JP2010193702A - Apparatus and method for controlling induction motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for controlling an induction motor, capable of being constructed at low cost and suppressing generation of an inrush current caused by star-delta switching. <P>SOLUTION: The apparatus for controlling an induction motor includes: first switches 110, 111, 112 for star-connecting a three-phase coil of the induction motor 300; second switches 120, 121, 122 for delta-connecting the three-phase coil; boosting circuits 150, 151, 152 for generating a boosting voltage obtained by boosting a power voltage of a power supply for driving the induction motor 300; third switches 160, 161, 162, 170, 171, 172, 180, 181, 182 for selecting a power voltage or boosting voltage so that the power voltage or the boosting voltage may be applied to the three-phase coil; and a control circuit 210 for controlling the first to third switches so that a boosting voltage may be applied to the star-connected three-phase coil after application of a power voltage and then power voltage may be applied to the delta-connected three-phase coil. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction motor control device and an induction motor control method.

  The star-delta starting method is widely used for starting induction motors, particularly squirrel-cage induction motors. This start-up system is often used for blowers, pumps, turbo blowers, and those that want to turn torque softly at the beginning of the start, for example, refrigerators and compressors. The voltage of 7% is theoretically fixed, and the voltage difference when shifting to the delta connection is large, which causes electrical and mechanical troubles. In particular, when used as a motor start circuit, a large current may flow in which the inrush current when switching from the star to the delta far exceeds the current when the delta circuit is directly input. In addition, the mechanical shock caused by this is inevitably caused by the stagnating torque several times the starting torque when it is put directly into the delta circuit. Damage and shortening of life are inevitable.

  For example, Patent Document 1 discloses an open circuit transition system in which an induction motor coil is temporarily disconnected from a power source when the induction motor is accelerated to a predetermined speed and then switched from star connection to delta connection. However, since the phase of the residual voltage in the coil does not match the phase of the power supply voltage, an excessive inrush current may occur depending on the phase difference between the two, welding of the contact of the magnetic contactor, power supply voltage A control circuit using a closed circuit transition system is shown in which the coil is not disconnected from the power source because troubles such as abnormal drop of the current and trip of the overcurrent breaker are likely to occur.

  That is, in the star delta starting device for an induction motor disclosed in Patent Document 1, a condition for appropriately setting the resistance value of the starting resistor inserted into each coil of the induction motor from the star connection state to the transient delta connection state. When the induction motor is in the transient delta connection state, the starting resistance at the maximum torque generation speed is not inserted, and when the switching to the transient delta connection of the induction motor in which the starting resistance is inserted for the torque to be possessed Set the torque ratio to a value between 1/4 and 1/3, or a value around 1/3, and suppress the value of inrush current that occurs when switching from star connection to delta connection. The induction motor can be started smoothly and reliably.

  Further, in Patent Document 2, the motor impedance seen from the power supply side changes suddenly to 1/3 when the coil is switched between the star connection and the delta connection, so that the current from the power supply is tripled. Since the converter may exceed the allowable current capacity limit range, the star connection and delta connection are alternately switched at a constant ratio by an electronic switch in order to seamlessly switch the star connection and delta connection coils steplessly. A star delta controller is shown which is adapted to switch to

JP 2000-116164 A JP 2001-339990 A

  However, the closed circuit transition method disclosed in Patent Document 1 switches the star connection to the delta connection while connecting or disconnecting the starting resistor to the coil, so that the coil is not disconnected from the power source, and an excessive inrush current is generated. Although there is an advantage that it does not occur, when the capacity increases, a resistor having a large capacity is required, and the cost increases accordingly.

  Further, in the star / delta control device disclosed in Patent Document 2, the control circuit for alternately switching the star connection and the delta connection at a constant ratio must be complicated and expensive, and an inverter is used. The method itself is expensive and has a short life. Moreover, since the inverter has a loss of several percent, if the loss during that period is converted into a monetary amount, the amount becomes so large that a new inverter control device can be purchased, which causes a problem in terms of cost.

  Therefore, an object of the present invention is to provide an induction motor control device that can be configured at low cost and can suppress the occurrence of an inrush current associated with star / delta switching.

  In order to solve the above-mentioned problem, an induction motor control device according to one aspect of the present invention includes a first switch for setting a three-phase coil of an induction motor to star connection, and a delta connection for the three-phase coil. The second switch, a booster circuit that generates a boosted voltage obtained by boosting the power supply voltage of the power supply for driving the induction motor, and the power supply voltage or the boosted voltage is applied to the three-phase coil. A third switch that selects a power supply voltage or the boosted voltage, and the boosted voltage is applied after the power supply voltage is applied to the star-connected three-phase coil, and then the delta-connected three-phase coil A control circuit that controls the first to third switches so that the power supply voltage is applied, and the booster circuit applies the boosted voltage to the star-connected three-phase coil. The voltage of the three-phase coil is higher than the voltage of the three-phase coil when the power supply voltage is applied to the star-connected three-phase coil, and the voltage of the three-phase coil is delta-connected. The power supply voltage is boosted so as to be lower than the voltage of the three-phase coil when the power supply voltage is applied.

In order to solve the above problems, an induction motor control method according to one aspect of the present invention includes:
In the induction motor control method for switching and controlling the coil in the induction motor connected to the three-phase power source between star connection and delta connection,
In the star connection state of the induction motor coil, an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state is applied to the induction motor coil, and the induction motor rotates at a constant rotational speed. When reaching the state, the application of the intermediate voltage is stopped and switching to the delta connection is performed, and the induction motor is accelerated in the star connection state and then switched to the delta connection.

And the apparatus which implements this induction motor control method is
Switching between an induction motor connected to a three-phase power source, a first switch having a star connection for a coil of the induction motor and a second switch having a delta connection, and the first switch and the second switch; In the induction motor control device having the control means for starting the induction motor with star connection and driving with delta connection,
Booster that is provided corresponding to each phase of the three-phase power source and applies a voltage that is an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state to the coil in the star connection state A state in which the voltage boosted by the step-up transformer is applied to a corresponding coil of the induction motor in a star connection state by the transformer and the first switch, and the induction motor has reached a rated rotational speed in the star connection And a plurality of switch groups for separating the step-up transformer, and the control means controls the switch group to apply a voltage boosted by the step-up transformer in a star connection state to the induction motor coil, The step-up transformer is disconnected while the electric motor rotates at a constant rotational speed, and the second switch forms a delta connection. And controlling so as to shift to.

  Thus, in the star connection state, by applying an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state to the induction motor coil, thereby accelerating the induction motor and switching to the delta connection, Since the voltage applied to the induction motor coil is intermediate, the voltage difference at the time of star / delta switching becomes small, so that the star / delta can be switched smoothly. In addition, by applying the intermediate voltage with a step-up transformer, the transformer is cheaper and has a longer life than the inverter, and the configuration can be simplified. Therefore, the induction motor control device itself can be provided at a lower cost.

  And in order to perform the application and separation of the intermediate voltage by the step-up transformer, the plurality of switch groups include a third switch connected between each phase of the three-phase power source and a corresponding coil of the induction motor, A fourth switch provided between one end of the primary side of each step-up transformer and each phase of the three-phase power supply; a coupling point coupled to the other end of the primary side of each step-up transformer; and the primary And a step-up side of the step-up transformer is connected between the third switch and the induction motor coil, so that an intermediate voltage can be obtained with a very simple configuration. Can be applied and disconnected. In addition, although these switch groups can be made inexpensive and have a long life by being composed of ordinary relays or the like, it is needless to say that they may be composed of semiconductor elements.

  The intermediate voltage between the coil voltage in the star connection state and the coil voltage in the delta connection state is applied in a state where the current of the induction motor coil becomes a constant value after the star connection. , A means for detecting the current flowing in the induction motor coil and a means for detecting the number of revolutions of the induction motor, and the control means is in a star connection state by the first switch, and the induction motor current from the current detection means is In response to the signal reaching the constant value state, the voltage boosted by the step-up transformer is applied to the induction motor coil, and the induction motor rotation speed from the induction motor rotation speed detection means is received. Stop application of the boost voltage from the boost transformer to the induction motor coil, and shift to the delta connection state by the second switch. Since it is configured to control ON / OFF of the switch group, the current flowing in the coil of the induction motor, the application of the boost voltage to the coil at the rotation speed, and the transition to the delta connection are performed, so that the star connection and acceleration are performed. Thus, the inrush current associated with the switching to the delta connection is not generated, and the switching can be performed reliably and efficiently.

  Further, an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state is generated by a step-up transformer, and the three-phase power source is connected to the induction motor coil when starting the induction motor The intermediate voltage is applied to the induction motor coil after the voltage drop of the three-phase power supply is recovered by operating a part of the step-up transformer as a reactor by passing a part of the step-up transformer. And a voltage detection means for the three-phase power supply, and the control means is connected to the three-phase power supply through a part of the step-up transformer in a star connection state by a first switch accompanying the start of the induction motor. Connected to the induction motor coil, receives a voltage drop recovery signal of the three-phase power supply by the voltage detection means and stops part of the step-up transformer The three-phase power supply is directly connected to the induction motor coil, and the voltage boosted by the step-up transformer is applied to the induction motor coil in response to the recovery signal of the voltage drop of the three-phase power supply by the voltage detecting means. Since the switch group is configured to control ON / OFF of the switch group so as to shift to the state, the voltage initially applied to the induction motor coil is connected to the reactor via a part of the step-up transformer. In the same state, a low voltage is applied, the next three-phase power is directly applied to the induction motor coil in the star connection state, the boosted voltage is applied, and the voltage by the delta connection is applied. Then, a high voltage is sequentially applied in four stages. Therefore, for example, when the three-phase power source is a generator, a generator having a capacity about three times the rated current is required when the star connection is directly shifted to the delta connection. In this embodiment, the voltage drop at each stage is 1 Since it is / 4, a generator with a small capacity of about 1 or 1.1 times the rated current is sufficient, and star delta switching can be performed economically. Moreover, even if a plurality of induction motors happen to start at the same time, there will be no problem because the respective inrush currents are small.

  It is possible to provide an induction motor control apparatus that can be configured at low cost and can suppress the occurrence of an inrush current associated with star / delta switching.

It is a figure which shows the structure of the induction motor control apparatus which is one Embodiment of this invention. It is an example of the flowchart which an induction motor control apparatus performs in Example 1. FIG. It is an example of the timing chart for demonstrating operation | movement of the induction motor control apparatus in Example 1. FIG. It is an example of the flowchart which an induction motor control apparatus performs in Example 2. FIG. It is an example of the timing chart for demonstrating operation | movement of the induction motor control apparatus in Example 2. FIG. It is a figure which shows the structure of the starter 100 which is one Embodiment of this invention. FIG. 3 is a diagram showing details of a coil 150. 3 is a flowchart for explaining the operation of the starter 100. 4 is a diagram for explaining a current flowing in a coil 150. FIG. It is a figure which shows the structure of the starter 500 which is one Embodiment of this invention.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Absent.

  In the induction motor control device shown in FIG. 1, when switching a coil (three-phase coil) in an induction motor connected to a three-phase power source to a star connection and a delta connection, the voltage of the coil in the star connection state is changed in the star connection state. And an intermediate voltage of the coil voltage in the delta connection state is applied to the induction motor coil, thereby accelerating the induction motor and thereafter switching to the delta connection.

  In this way, the voltage applied to the induction motor coil is the intermediate voltage, so that the voltage difference at the time of star / delta switching becomes small, and the star / delta can be switched smoothly accordingly. In addition, since the intermediate voltage is applied by the step-up transformer and a plurality of switch groups, the transformer is cheaper and has a longer life compared to the inverter, and the configuration can be simplified. Can be provided.

  The intermediate voltage is applied when the current of the induction motor coil is constant after the star connection, and the transition to the delta connection is performed when the induction motor is in the constant rotation speed state. Inrush current associated with switching to connection, acceleration, and transition to delta connection is not generated, and switching can be performed efficiently and reliably.

  In addition, as an initial start when the star connection state is established, the voltage application from the three-phase power source to the induction motor coil is routed through a part of the step-up transformer, and the reactor is interposed between the coil voltage in the star connection state. A lower voltage can be applied. In this way, a low voltage is applied to the induction motor before voltage application by the star connection, and then the three-phase power source is boosted in a state where the three-phase power source is directly applied to the induction motor coil in the star connection state. A state where an intermediate voltage is applied, a state where a voltage due to delta connection is applied, and a higher voltage can be sequentially applied in four stages. Therefore, even if the three-phase power supply is a generator, for example, the voltage drop at each stage is 1/4, so a generator with a small capacity of about 1 or 1.1 times the rated current is sufficient, It is possible to perform star / delta switching.

== Example 1 ==
FIG. 1 is a block diagram showing the configuration of an induction motor control device according to an embodiment of the present invention, FIG. 2 is a flowchart executed by the induction motor control device, and FIG. 3 explains the operation of the induction motor control device. It is a timing chart for. For the sake of explanation, the timing chart in FIG. 3 is different from the actual time interval. The “start (star)” shown at the top indicates the period during which the induction motor is started by star connection. "Voltage increase" indicates that the boosted voltage is applied to the coil of the induction motor in the star connection state and acceleration is performed, and "operation (delta)" indicates the operation state as delta connection. “PB” in (1) indicates that the induction motor is started by a push button. In the time chart, it is illustrated that the induction motor is operating until the induction motor is stopped. It is preferable that only the self-holding type is used, and it is only necessary to operate in such a manner, so that it does not stick to the push button.

  (2) to (5) show the ON / OFF states of SW1 to SW5 in FIG. 1, and (7) shows that the signal is generated in a state where the current of the induction motor at the start exceeds a constant state Im. Thus, it may be possible to measure the time until the current of the induction motor reaches the constant state Im in advance during a test run and to switch the switch by issuing a signal as shown in the figure by a timer. (8) indicates that a signal is generated when the number of revolutions of the induction motor (motor) exceeds N where the number of revolutions of the induction motor (motor) exceeds a constant value. It is also possible to measure the time until this occurs and switch the switch by issuing a signal as shown in the figure using a timer.

  Note that the timer that measures the time until the current of the induction motor reaches the constant state Im is a timer that starts measuring after the power supply voltage is applied to the star-connected three-phase coil, although not shown in FIG. For example, it is provided inside the control circuit 22. In addition, the timer that measures the time until the rotation speed of the induction motor reaches the fixed rotation speed N is a timer that starts measuring time after the boosted voltage is applied to the star-connected three-phase coil. However, for example, it is provided inside the control circuit 22.

  In FIG. 1, 10 is a control device that controls star / delta switching of the induction motor, and 12 is a plurality of switches SW4a, SW4b for connecting a three-phase power source 36 to a step-up transformer (Ta, Tb, Tc) 18. A fourth switch consisting of SW4c, 14 is a third switch consisting of SW3a, SW3b, SW3c for connecting the three-phase power source 36 to the coil (winding) of the induction motor (motor) 30, and 16 is a step-up transformer (Ta , Tb, Tc) 18 for boosting voltage switching for switching to, for example, 70% or 75% of the coil voltage of the induction motor (motor) 30 in the delta connection state according to the load of the induction motor (motor) 30 This tap switch 16 does not need to be switched if the load is constant. Reference numeral 20 denotes a fifth switch composed of SW5a, SW5b, and SW5c for switching connection / disconnection to the coupling point that couples the opposite ends of the step-up transformer (Ta, Tb, Tc) 18 to the three-phase power source 36. 22 is a control circuit which is a control means for controlling star / delta switching, 24 is a current detector for detecting a current flowing in the coil of the induction motor 30, and 32 is a second switch for delta connection of the coil of the induction motor 30 ( SW2) and 34 are also the first switch (SW1) for star connection, 38 is a voltage detector for detecting the voltage of the three-phase power source 36, and 40 is the rotational speed for detecting the rotational speed of the induction motor (motor) 30. It is a detector. The control circuit 22 is, for example, a sequencer that performs processing as shown in FIGS. 2 and 4 described later, and controls the on / off of the first switch (SW1) 34 to the fifth switch (SW5) 20. To do. The step-up transformer (Ta, Tb, Tc) 18 is a so-called single-winding transformer. Furthermore, the coil of the induction motor (motor) 30 corresponds to a three-phase coil.

  Among them, the step-up transformer (T) 18 is connected to each phase of the three-phase power source 36 through the fourth switch (SW4) 12 as shown in the figure, and the other end is the fifth switch (SW5). The respective phases are coupled via 20, and the reverse side end of the fifth switch (SW 5) 20 is connected between the third switch (SW 3) 14 and the induction motor (motor) 30 as the boosting side. Yes. Further, as described above, the fourth switch (SW4) 12, the third switch (SW3) 14, and the fifth switch (SW3) 20 each have a plurality of switches to form a switch group. Note that these switch groups can be made inexpensive and have a long life by being composed of ordinary relays or the like, but of course may be composed of semiconductor elements such as thyristors. The step-up transformer (T) 18, the fourth switch (SW4) 12, and the fifth switch (SW5) 20 correspond to a step-up circuit. Furthermore, the control device 10, the current detector 24, the voltage detector 38, and the rotation speed detector 40 correspond to the induction motor control device.

Induction motor control apparatus 10 for controlling the (motor) 30 of the star-delta switching is started the process in step S10 shown in the flow diagram of FIG. 2, step S12, i.e., at time t ₁ in FIG. 3 (1) 2 is turned on, the first switch (SW1) 34 for star connection, the third switch (SW3) as shown in step S14 of FIG. 2, and (2) and (4) of FIG. ) 14 is turned ON. Therefore, the induction motor (motor) 30 is started in a star connection state. In the meantime, the fourth switch (SW4) 12 for applying the voltage from the three-phase power source 36 to the step-up transformer (T) 18 is turned on at step S16 in FIG. ₂ and time t2 in FIG.

Then, the control circuit 22 detects the current flowing through the coil of the induction motor (motor) 30 by the current detector 24 in step S18 of FIG. 2, and the current is converted into a star in the predetermined induction motor (motor) 30 in step S20. If the current exceeds the fixed current Im at the time of connection, that is, if a timer is used as described above, it is determined whether or not it is a problem at that time. If not reached (if the time set in the timer is not reached), step returning to S18, (when it becomes the time set in the timer) and has a place beyond issues a signal at time t ₃ as shown in FIG. 3 (7), the process proceeds to step S22.

Then, in step S22 in FIG. 2, the control circuit 22 performs a third switch (direct connection of the induction motor (motor) 30 in FIG. 1 with the star connection as shown in (4) and (6) in FIG. The SW3) 14 is turned off, and the fifth switch (SW5) 20 that couples one ends of the step-up transformer (T) 18 to each other is turned on. Therefore, the three-phase power source 36 is connected to the induction motor (motor) 30 via the step-up transformer (T) 18, and the boosted voltage is applied to the induction motor (motor) 30, so that the induction motor (motor) is 30 is accelerated. At this time, the step-up transformer (T) 18 has a boost voltage of an intermediate voltage between the coil voltage in the star connection state of the induction motor 30 and the coil voltage in the delta connection state, that is, 2 of the coil voltage in the star connection state. The winding ratio of the step-up transformer (T) 18 is determined so that the voltage becomes approximately 70% of the coil voltage in the delta connection state.

In this state, the control circuit 22 detects the rotation speed of the induction motor (motor) 30 by the rotation speed detector 40 of FIG. 1 in step S24 of FIG. 2, and the rotation speed is constant rotation in the star connection state in step S26. It is determined whether or not the rotation state has been reached by a number N, that is, when the timer is used as described above, and whether or not the time has been reached. returning to S24 repeat the same thing, (when it becomes the time set in the timer) if reached emits a signal at time t ₄ as shown in (8) in FIG. 3, the process proceeds to step S28.

  In step S28, as shown in (2) and (6) of FIG. 3, the first switch (SWI) 34 for star connection and the end of the step-up transformer (T) 18 are coupled to each other. The switch (SW5) 20 is turned off, and the second switch (SW2) 32 for delta connection and the three-phase power source 36 are directly connected to the induction motor (motor) as shown in (3) and (4) of FIG. The third switch (SW3) 14 for connection to 30 is turned ON to switch to the delta connection.

Therefore, the induction motor (motor) 30 is driven by a delta connection and enters an operating state. In addition, after that, when the fourth switch (SW4) 12 for connecting the three-phase power source 36 to the step-up transformer (T) 18 is turned OFF in step S30 of FIG. 2, the induction motor (motor) 30 is stopped. 2 of step S32, the PB is OFF at time t ₅ in (1) in FIG. 2, the processing in step S34 induction motor (motor) 30 is stopped and completed.

  By switching the star / delta of the induction motor (motor) 30 in this way, the voltage applied to the induction motor coil is an intermediate voltage so that the voltage difference at the time of star / delta switching is small, and in the star connection state. By applying a voltage higher than that in the star state, the induction motor (motor) 30 is accelerated, and the star / delta can be smoothly switched accordingly. In addition, by applying the intermediate voltage with a step-up transformer, the transformer is cheaper and has a longer life than the inverter, and the configuration can be simplified. Therefore, the induction motor control device itself can be provided at a lower cost.

== Example 2 ==
Next, a second embodiment of the control method for star / delta switching of the induction motor will be described. In the second embodiment, as an initial start when the star connection state is established, the voltage application from the three-phase power source to the induction motor coil is routed through a part of the step-up transformer 18 and the reactor is interposed. A voltage lower than the coil voltage in the star connection state is applied. In this case, a low voltage is applied to the induction motor (motor) 30 before the voltage application by the star connection, and then the three-phase power source is directly applied to the induction motor coil that is star-connected. It is possible to apply an intermediate voltage obtained by boosting the voltage to the induction motor coil connected in a star connection, a state in which a voltage by delta connection is applied, and a high voltage sequentially in four stages.

  The second embodiment will be described in accordance with the flow chart shown in FIG. 4 and the time chart shown in FIG. 5, using the control block diagram of FIG. 1 as it is. For the sake of explanation, the timing chart of FIG. 5 is different from the actual time interval. “Initial” shown at the top is in the star connection state, and a part of the step-up transformer 18 is used as a reactor. Then, in the initial start state in which a low voltage is applied, “start (star)” stops a part of the step-up transformer 18 as a reactor, and the period for starting the induction motor by the star connection is set to “acceleration ( "Star boosting" indicates that the boosted voltage is applied to the coil of the induction motor in the star connection state and acceleration is performed, and "operation (delta)" indicates that the operation is in the delta connection state. “PB” in (11) is a push button for starting the induction motor, and preferably has a type in which only the ON signal is self-held as described above. (12) to (15) show the ON / OFF states of SW1 to SW5 in FIG. 1, (17) and (18) show that the voltage drop of the three-phase power supply 36 at the time of initial startup and start-up by star connection is restored. It shows that a signal is emitted in the state of voltage V (the original voltage of the three-phase power supply 36), and this measures the time until the voltage drop of the induction motor recovers to V in advance during a trial run. In addition, the switch may be switched by issuing a signal as shown in the figure using a timer. (19) indicates that a signal is generated when the number of revolutions of the induction motor (motor) exceeds N where the number of revolutions of the induction motor exceeds a constant value. It is also possible to measure the time until this occurs and switch the switch by issuing a signal as shown in the figure using a timer.

  In the star / delta switching control method of the first embodiment described above, a voltage is directly applied from the three-phase power source 36 to the star-connected induction motor (motor) 30 when starting the induction motor (motor) 30. In this case, the value is Although it is low, inrush current occurs. Therefore, for example, when the induction motor (motor) 30 is driven by a private generator, it is necessary to provide a private generator having a current capacity larger than the rated current of the induction motor (motor) 30. In the switching control method, as described above, star delta switching can be performed economically with a generator having a small capacity of about 1 or 1.1 times the rated current.

Flow processing in step S40 shown in diagram of Fig. 4 is started, step S42, i.e., when the PB shown in the time t ₆ (1) of FIG. 5 is turned ON, step S44 in FIG. 4, FIG. 5 As shown in (12) and (15), the first switch (SWI) 34 and the fourth switch (SW4) 12 for star connection are turned ON. Therefore, a voltage is applied to the coil of the induction motor (motor) 30 from the three-phase power source 36 via the fourth switch (SW4) 12 and the step-up transformer (T) 18, and the power input to the step-up transformer (T) 18 is applied. The coil from the end to the boost side end acts as a reactor, causing a voltage drop, and a lower voltage is applied accordingly.

  If this voltage is about 40% of the coil voltage at the time of delta connection, the induction motor (motor) 30 may not rotate. In this case, it is connected to the coil of the induction motor (motor) 30. Since the voltage drop due to the above is recovered in a short time, the control circuit 22 monitors the voltage of the three-phase power source 36 with the voltage detector 38 of FIG. 1 in step S46, and the initial starting voltage drop is recovered in step S48. It is determined whether or not the predetermined voltage V has been reached, that is, whether or not that time has been reached in the case of using the evening imager as described above. If not recovered (when the time set in the timer is not reached), the process returns to step S46 to continue monitoring the voltage. If recovered (when the time set in the timer is reached), the process proceeds to step S50.

Control circuit at step S50 22, as shown in FIG. 5 (17), and outputs a signal at time t ₇ as an initial starting voltage V has recovered, the third switch (SW3) 14 to ON, the fourth The switch (SW4) is turned off and the voltage of the three-phase power source 36 is applied as it is to the coil of the induction motor (motor) 30 in the star connection state, so that the start state in the star connection state is obtained. In this state, the control circuit 22 monitors the voltage of the three-phase power source 36 with the voltage detector 38 of FIG. 1 and recovers the starting voltage drop caused by the star connection state in step S52 and recovers the predetermined voltage. If it is V, that is, if the timer is used as described above, it is determined whether or not the time has been reached, and if it has not recovered (when the time set in the timer has not been reached), monitoring continues and recovery If it is (when the time set in the timer is reached), the process proceeds to step S54.

Control circuit 22 in this step S54, as shown in FIG. 5 (18), and outputs a signal at time t ₈ as the starting voltage has recovered to the V, (14), as shown in (15), The third switch (SW3) 14 having the induction motor (motor) 30 in FIG. 1 as a direct star connection is turned OFF, and the fourth switch (SW4) and one end of the step-up transformer (T) 18 are coupled to each other. Switch (SW5) 20 is turned ON. Therefore, the three-phase power source 36 is connected to the induction motor (motor) 30 via the step-up transformer (T) 18, and the boosted voltage is applied to the induction motor (motor) 30, so that the induction motor (motor) is 30 is accelerated. The boost voltage of the step-up transformer (T) 18 at this time is an intermediate voltage between the coil voltage in the star connection state of the induction motor (motor) 30 and the coil voltage in the delta connection state, that is, as described above, the star connection state. The coil voltage is increased by 20% and is approximately 70% of the coil voltage in the delta connection state.

In this state, the control circuit 22 detects the rotational speed of the induction motor (motor) 30 by the rotational speed detector 40 of FIG. 1 in step S56 of FIG. 4, and in step S58, the rotational speed is constant rotation in the star connection state. It is determined whether or not the number of revolutions N has been reached, that is, whether or not the time has been reached when using the timer as described above, and if it has not reached (when the time set in the timer has not been reached). It repeats the same returns to the step S56, if reached (when it becomes the time set in the timer), as shown in (19) in FIG. 5, emits a signal at time t _9, the step S60 move on.

  In step S28, as shown in (12) and (66) of FIG. 5, the first switch (SW1) 34 for star connection and the end of the step-up transformer (T) 18 are coupled to each other. The switch (SW5) 20 is turned off, and the second switch (SW2) 32 for delta connection and the three-phase power source 36 are directly connected to the induction motor (motor) as shown in (13) and (14) of FIG. The third switch (SW3) 14 for connection to 30 is turned ON to switch to the delta connection.

Therefore, the induction motor (motor) 30 is driven by a delta connection and enters an operating state. After that, when the fourth switch (SW4) 12 for connecting the three-phase power source 36 to the step-up transformer (T) 18 is turned OFF in step S62 of FIG. 2, the induction motor (motor) 30 is stopped as shown in FIG. In step S64, at time _t10 in (1) of FIG. 5, the PB is turned OFF, the induction motor (motor) 30 is stopped, and the process ends in step S66.

  In this way, the voltage applied to the coil of the induction motor (motor) 30 is set to the initial starting voltage shown in step S44, the star connection starting voltage shown in step S50, the boosted voltage in the star connection state shown in step S54, step S60. As shown in step S48 and step S52, it is determined whether or not the voltage drop has been recovered and the next step is performed. Has moved to. Therefore, for example, when the three-phase power source 36 is a generator as described above, a generator having a capacity about three times the rated current is required when the star connection is directly changed to the delta connection. The voltage drop at is 1/4, and a generator with a small capacity of about 1 or 1.1 times the rated current is sufficient, and star-delta switching can be performed economically.

  The induction motor control device can be configured with a simple configuration at a low cost and with a long service life, and it is possible to switch the star delta efficiently without causing an inrush current due to the switching. As a method and apparatus, it has a great effect.

== First embodiment of the starter ==
The structure of the starter which is one Embodiment of this invention is demonstrated. FIG. 6 is a diagram illustrating a configuration of a starter 100 that is the first embodiment of the starter. The starter 100 (induction motor control device) is a device for receiving a voltage of a three-phase power source and starting a squirrel-cage induction motor (hereinafter simply referred to as a motor) 300. Switches 110 to 112, 120 to 122, 130 to 133, 160 to 162, 170 to 172, 180 to 182, coils 150 to 152, timer 200, and control circuit 210. Motor 300 is a three-phase motor including three-phase coils L1 to L3.

  The switches 110 to 112 are switches for setting the three-phase coils L1 to L3 to star connection. When all of switches 110-112 are turned on, three-phase coils L1-L3 are star-connected. The switches 110 to 112 are relay switches that are turned on / off based on the control of the control circuit 210. Although not specifically described below, the other switches of the present embodiment are relay switches that are controlled to be turned on and off by the control circuit 210, similarly to the switches 110 to 112.

  The switches 120 to 122 are switches for delta connection of the three-phase coils L1 to L3 of the motor 300. When all of switches 120-122 are turned on, three-phase coils L1-L3 are delta-connected. In this embodiment, the node to which the three-phase coil L1 and the switch 120 are connected is the node A, the node to which the three-phase coil L2 and the switch 121 are connected is the node B, and the three-phase coil L3 and the switch 122 are Let the node to be connected be node C. The switches 110 to 112 correspond to a first switch, and the switches 120 to 122 correspond to a second switch.

  A U-phase voltage Vu of the three-phase power source is applied to the switch 130, a V-phase voltage Vv of the three-phase power source is applied to the switch 131, and a W-phase voltage Vw of the three-phase power source is applied to the switch 132. Is applied.

  The coil 150 generates a boosted voltage obtained by boosting the voltage Vu at the terminal Ta. The coil 150 includes a tap terminal (hereinafter simply referred to as a tap) t0 and a tap t10 between one terminal Ta (first terminal) and the other terminal Tb (second terminal). The terminal Ta is connected to the switch 170, and the terminal Tb is connected to the switch 160. The tap t0 (third terminal) is connected to the switch 130, and the tap t10 (fourth terminal) provided between the tap t0 and the terminal Tb is connected to the switch 180. In FIG. 6, the coil 150 is illustrated in a simplified manner for the sake of easy understanding of the configuration of the starter 100, but the actual coil 150 is, for example, a single-turn transformer 400 as illustrated in FIG. 7. The iron core 410 is wound around. Note that the coil 150 of the present embodiment is wound N1 times from the terminal Ta to the tap t0 and N2 times from the tap t0 to the tap t10, for example.

  One end of the switch 160 is connected to the terminal Tb, and the other end is connected to the switches 161 and 162. For this reason, when the switches 160 to 162 are turned on, the coils 150 to 152 are star-connected. That is, the node to which each of the switches 160 to 162 is connected is a so-called neutral point. In a state where the coils 150 to 152 are star-connected, the coils 150 to 152 operate as boosting coils that boost the voltage at the tap t0. For this reason, when the voltage Vu is applied to the tap t0, a boosted voltage obtained by boosting the voltage Vu is generated at the terminal Ta. Note that the switches 160 to 162 correspond to a fourth switch.

  The coil 151 generates a boosted voltage obtained by boosting the V-phase voltage Vv of the three-phase power source at the terminal Tc. The coil 152 generates a boosted voltage obtained by boosting the W-phase voltage Vw of the three-phase power source at the terminal Te. Since the coils 151 and 152 are the same as the coil 150, detailed description of the coils 151 and 152 is omitted.

  The switch 170 connects the terminal Ta of the coil 150 and the node A, the switch 171 connects the terminal Tc of the coil 151 and the node B, and the switch 172 connects the terminal Te of the coil 152 and the node C. . Note that the switches 170 to 172 correspond to a fifth switch.

  The switch 180 connects the tap t10 of the coil 150 and the node A, the switch 181 connects the tap t11 of the coil 151 and the node B, and the switch 182 connects the tap t12 of the coil 152 and the node C. . Note that the switches 180 to 182 correspond to a sixth switch. The switches 160 to 162, 170 to 172, and 180 to 182 correspond to a third switch.

  For example, the timer 200 measures the time from when the switches 130 to 132 are turned on and the power sources Vu, Vv, and Vw are applied to the taps t0 to t2.

  The control circuit 210 (control circuit) is a sequencer that controls on / off of the above-described switch at a predetermined timing when a start signal for starting the motor 300 is input. The start signal is provided, for example, in an operation unit (not shown) of the starter 100, and is generated when a user turns on a start switch (not shown) for starting the motor 300. The control circuit 210 first star-forms the three-phase coils L1 to L3, and gradually increases the voltage applied to the three-phase coils L1 to L3 during that time. Thereafter, the control circuit 210 drives the motor 300 by delta-connecting the three-phase coils L1 to L3.

  Specifically, when the start signal is input, the control circuit 210 turns on the switches 110 to 112 and the switches 180 to 182 and then turns on the switches 130 to 132. Hereinafter, a state in which the switches 110 to 112, 130 to 132, and 180 to 182 are turned on is referred to as a first state.

  Thereafter, when the time measured by the timer 200 reaches a predetermined time T1, the control circuit 210 turns on the switches 170 to 172 in addition to the switches 110 to 112, 130 to 132, and 180 to 182 that are turned on. Hereinafter, a state in which the switches 110 to 112, 130 to 132, 170 to 172, and 180 to 182 are turned on is referred to as a second state.

  When the time measured by the timer 200 reaches a predetermined time T2 (> T1), the control circuit 210 switches the switch 180 among the switches 110 to 112, 130 to 132, 170 to 172, and 180 to 182 that are turned on. After ˜182 is turned off, the switches 160 to 162 are turned on. Hereinafter, a state in which the switches 110 to 112, 130 to 132, 160 to 162, and 170 to 172 are turned on is referred to as a third state.

  Further, when the time measured by the timer 200 reaches a predetermined time T3 (> T2), the control circuit 210 switches the switch 110 among the switches 110 to 112, 130 to 132, 160 to 162, and 170 to 172 that are turned on. After turning off .about.112 and 160 to 162, the switches 120 to 122 and 180 to 182 are turned on. Hereinafter, a state in which the switches 120 to 122, 130 to 132, 170 to 172, and 180 to 182 are turned on is referred to as a fourth state.

  In addition, a series of control for the switch of the control circuit 210 at the time T1 to T3 is executed in a sufficiently short time.

== Operation of Starter 100 ==
Here, the operation of the starter 100 will be described with reference to the flowchart shown in FIG. The main body of each process in the flowchart of FIG. In the initial state before the start switch (not shown) is turned on, all the switches of the starter 100 are turned off.

  First, when a user turns on a start switch (not shown), a start signal is input to the control circuit 210 (S100). As a result, the control circuit 210 turns on the switches 130 to 132 after turning on the switches 110 to 112 and 180 to 182 (S101).

  Here, a part of the coil 150 (winding of the number of turns N2) exists from the tap t0 to the tap t10. Therefore, when the switches 130 and 180 are turned on, a current corresponding to the voltage Vu is supplied to the node A through a part of the winding of the coil 150 described above. The same applies to the node B when the switches 131 and 181 are turned on and the current supplied to the node C when the switches 132 and 182 are turned on. For this reason, when the process 101 is executed, the three-phase coils L <b> 1 to L <b> 3 that are star-connected are started so-called reactors. In the present embodiment, taps t0 to t2 and tap t10 are set so that the voltage of the three-phase coils L1 to L3 when the motor 300 is being reactor started (process: S101) is, for example, 29% of the power supply voltage. Suppose that the position of -12 is defined.

  As described above, when the switch 130 is turned on and the power supply voltage Vu is applied to the tap t0, the timer 200 starts measuring time. When the time measured by the timer 200 reaches time T1 (S102: YES), the control circuit 210 further turns on the switches 170 to 172 (S103).

  When the switch 170 is turned on, for example, as shown in FIG. 9, the coil 150 includes a tap t0, a coil 150, a tap t10, a current Ia flowing to the node A via the switch 180 in this order, a tap t0, a coil A current Ib that flows to the node A through the 150, the terminal Ta, and the switch 170 in sequence is newly generated. The current Ib flows in the opposite direction to the current Ia. The current Ib has a current value such that the ampere turns of the winding N1 and the winding N2 in the coil 150 are equal. That is, when the switch 170 is turned on, the current Ib flows such that the magnetic field of the iron core 410 becomes zero, so that the reactance component of the coil 150 becomes almost zero and the voltage at the node A becomes the voltage Vu. As a result, when the process S103 is executed, the power supply voltage is applied to the star-connected three-phase coils L1 to L3. When the power supply voltage is applied to the star-connected three-phase coils L1 to L3, the voltages of the three-phase motors L1 to L3 are about 58% of the power supply voltage. As described above, when the process S103 is executed, the voltage of the three-phase coils L1 to L3 of the motor 300 increases from 29% to 58% of the power supply voltage, so that the rotation speed of the motor 300 increases.

  When the time measured by the timer 200 reaches time T2 (> T1) (S104: YES), the control circuit 210 is turned on among the switches 110-112, 130-132, 170-172, 180-182 that are turned on. After the switches 180 to 182 are turned off, the switches 160 to 162 are turned on (S105). As described above, for example, when the switch 160 is turned on and the voltage Vu is applied to the tap t0, a boosted voltage higher than the power supply voltage is generated at the terminal Ta. Therefore, in the process 105, a boosted voltage higher than the power supply voltage is applied to the star-connected three-phase coils L1 to L3. For this reason, since the voltage of the three-phase coils L1 to L3 of the motor 300 further increases from 58% of the power supply voltage, the rotation speed of the motor 300 increases. The voltage of the three-phase coils L1 to L3 when the boosted voltage is applied to the star-connected three-phase coils L1 to L3 is higher than the value of 58% of the power supply voltage and from the value of 100% of the power supply voltage. It is assumed that the positions of taps t0 to t2 are designed so as to be low. Specifically, in this embodiment, when the boosted voltage is applied to the star-connected three-phase coils L1 to L3, the voltage of the three-phase coils L1 to L3 is, for example, a tap so as to be 70% of the power supply voltage. The positions of t0 to t2 are determined.

  When the time measured by the timer 200 reaches time T3 (> T2) (S106: YES), the control circuit 210 includes the switches 110 to 112, 130 to 132, 160 to 162, and 170 to 172 that are turned on. After the switches 110 to 112 and 160 to 162 are turned off, the switches 120 to 122 and 180 to 182 are turned on (S107).

  When the switches 110 to 112 are turned off and the switches 120 to 122 are turned on, the three-phase coils L1 to L3 are in delta connection. Similarly to the process S103, when the switches 160 to 162 are turned off and the switches 170 to 172 and 180 to 182 are turned on, the voltages of the nodes A to C become voltages Vu, Vv, and Vw, respectively. Therefore, when the process S107 is executed, the power supply voltage (100%) is applied to the three-phase coils L1 to L3 that are delta-connected. And if process S107 is performed, the starter 100 will continue to drive the motor 300 with a power supply voltage.

  Thus, by using the starter 100, the voltage applied to the three-phase coils L1 to L3 gradually increases to about 29%, about 58%, about 70%, and 100% of the power supply voltage. Therefore, the starter 100 can smoothly accelerate the motor 300 while suppressing the starting current, particularly the inrush current.

== Second embodiment of the starter ==
FIG. 10 is a diagram illustrating a configuration of a starter 500 that is the second embodiment of the starter. The starter 500 (induction motor controller) includes switches 110-112, 120-122, 130-133, 160-162, 170-172, 180-182, coils 150-152, timer 200, voltage detector 250, current. A detector 260, a rotational speed detector 270, and a control circuit 280 are included.
In the starter 500, the same reference numerals as those of the starter 100 shown in FIG. 6 are the same. Therefore, here, the voltage detector 250, the current detector 260, the rotation speed detector 270, and the control circuit 280 will be described.

The voltage detector 250 detects the levels of the voltages Vu, Vv, and Vw and outputs voltage signals indicating the respective levels to the control circuit 280.
The current detector 260 detects the currents Ix, Iy, and Iz supplied to the nodes A, B, and C, and outputs current signals indicating the respective current values to the control circuit 280.
The rotational speed detector 270 detects the rotational speed of the motor 300 and outputs a rotational speed signal indicating the rotational speed to the control circuit 280.
The control circuit 280 is a sequencer that controls a switch included in the starter 500 under a predetermined condition when a start signal for starting the motor 300 is input.

Specifically, when the start signal is input, the control circuit 280 sets the state of the switch included in the starter 500 to the first state described above.
Thereafter, the control circuit 280 determines whether the time measured by the timer 200 reaches the predetermined time T1, the levels of the voltages Vu, Vv, and Vw become the predetermined voltage V1, or the current values of the currents Ix, Iy, and Iz are predetermined. When the current value I1 becomes equal to or the rotational speed of the motor 300 reaches a predetermined rotational speed N1, the switch state is set to the second state described above. Here, condition 1 is a condition to be satisfied when the control circuit 280 sets the switch state to the second state.

  Then, the control circuit 280 determines whether the time measured by the timer 200 is a predetermined time T2 (> T1), the levels of the voltages Vu, Vv, and Vw are the predetermined voltage V2, or the currents Ix, Iy, and Iz. When the current value reaches a predetermined current value I2 or the rotational speed of the motor 300 reaches a predetermined rotational speed N2 (> N1), the switch state is set to the third state described above. Here, the condition to be satisfied when the control circuit 280 sets the switch state to the third state is defined as condition 2.

  Then, the control circuit 280 determines whether the time measured by the timer 200 is a predetermined time T3 (> T2), the levels of the voltages Vu, Vv, Vw are the predetermined voltage V3, or the currents Ix, Iy, Iz. When the current value reaches a predetermined current value I3 or the rotational speed of the motor 300 reaches a predetermined rotational speed N3 (> N2), the switch state is set to the aforementioned fourth state. Here, the condition to be satisfied when the control circuit 280 sets the switch state to the fourth state is defined as condition 3.

  Such a starter 500 operates in the same manner as the starter 100 shown in FIG. Specifically, when a start signal is input, the three-phase coils L1 to L3 are star-connected and the motor 300 is reactor-started. When condition 1 is satisfied, a power supply voltage is applied to the motor 300. When condition 2 is satisfied, a boosted voltage is applied to the motor 300. Furthermore, when the condition 3 is satisfied, the three-phase coils L1 to L3 are delta-connected, and a power supply voltage is applied to the motor 300. For this reason, even when the starter 500 is used, the motor 300 can be smoothly accelerated while suppressing the starting current of the motor 300.

  In the above, the starter 100,500 which is one Embodiment of this invention was demonstrated. For example, in the starter 100, the control circuit 210 switches 160 to 162, 170 to 172, 180 so that the boosted voltage is applied after the power supply voltage is applied to the three-phase coils L1 to L3 that are star-connected. Control ~ 182. Further, after that, the control circuit 210 uses the three-phase coils L1 to L3 as delta connections, and switches 110 to 112, 120 to 122, 160 to 162, and 170 to apply power supply voltages to the three-phase coils L1 to L3. 172, 180-182 are controlled. The voltage of the three-phase coils L1 to L3 when the boosted voltage is applied to the star-connected three-phase coils L1 to L3 is designed to be 70% of the power supply voltage, for example. For this reason, in this embodiment, the voltage of the three-phase coils L1 to L3 of the motor 300 increases in three stages, 58%, 70%, and 100%. For example, in this embodiment, compared with a general star / delta start in which a motor is started by applying a power supply voltage to a three-phase coil of delta connection after applying a power supply voltage to a three-phase coil of star connection The number of rotations of the motor 300 can be gradually increased while suppressing the inrush current of the three-phase coils L1 to L3. As a result, since the power supply voltages Vu, Vv, and Vw of the three-phase power supply can be suppressed from being lowered, it is not necessary to use a generator with a large capacity even when power is supplied from a generator or the like. Furthermore, unlike the techniques disclosed in Patent Documents 1 and 2, the starter 100 can be configured at low cost because it does not require expensive resistors or inverters.

  For example, the tap t10 is provided between the tap t0 and the terminal Tb. For this reason, when the switch 170 that connects the terminal Ta and the three-phase coil L1 and the switch 180 that connects the tap t10 and the three-phase coil L1 are turned on, as shown in FIG. The direction of flow is reversed. Furthermore, the currents Ia and Ib flow through the coil 150 so that the ampere turn from the tap t0 to the terminal Ta of the coil 150 is equal to the ampere turn from the tap t0 to the tap t10. As described above, by using the coil 150 having a general configuration that generates the boosted voltage, the tap t10 and the switch 180 that connects the tap t10 and the three-phase coil L1 are provided, so that the three-phase coils L1 to L3 are provided. A power supply voltage can be applied.

  In addition, when a start signal is input, the control circuit 210 turns on the switches 130 to 132 after turning on the switches 110 to 112 and the switches 180 to 182. Thereafter, the control circuit 210 turns on the switches 170 to 172 in addition to the switches 110 to 112, 130 to 132, and 180 to 182 that are turned on. Therefore, when starting the motor 300, the starter 100 applies a voltage of 29% of the power supply voltage before applying a voltage of 58% of the power supply voltage to the star-connected three-phase coils L1 to L3. The motor 300 can be reactor-started. Thus, in this embodiment, the voltage of the three-phase coils L1 to L3 of the motor 300 increases in four stages, 29%, 50%, 70%, and 100% of the power supply voltage. For this reason, the motor 300 can be started smoothly while reducing the starting current of the motor 300. Furthermore, the level of the boosted voltage is freely determined based on the position of the tap t0. Further, the voltage of the three-phase motor L1 when the reactor is started is freely determined based on the position of the tap t10. For this reason, the voltage of the three-phase coils L1 to L3 when the reactor is started and when the boost voltage is applied to the three-phase coils L1 to L3 is adjusted to a desired level by changing the positions of the taps t0 and t10. be able to. As a result, a voltage suitable for the motor driven by the starter 100 can be freely set, and the starting current and the like can be optimized according to the motor to be used.

  In addition, the starter 100 is provided with a timer 200 that measures the time after the power supply voltage is applied to the tap t0, that is, the time after the switch 130 is turned on. Then, when the time measured by the timer 200 reaches the time T1, the control circuit 210 controls the switch so that the power supply voltage is applied to the star-connected three-phase coils L1 to L3 from the reactor start. That is, the control circuit 210 can reliably accelerate the motor 300 when a predetermined time T1 has elapsed since the motor 300 was started.

  The control circuit 210 controls the switch so that the boosted voltage is applied to the star-connected three-phase coils L1 to L3 when the time measured by the timer 200 reaches the time T2. For this reason, the control circuit 210 can further accelerate the motor 300 at an appropriate timing.

  In addition, when the time measured by the timer 200 reaches time T3, the control circuit 210 controls the switches so that the star-connected three-phase coils L1 to L3 are changed to the delta connection and the power supply voltage is applied. For this reason, the control circuit 210 can accelerate the motor 300 while switching the four stages at appropriate timing.

  Further, the induction motor control device shown in FIG. 1 includes a first switch (SW1) 34 for setting the three-phase coil of the induction motor (motor) 30 to star connection, and a first switch for setting the three-phase coil to delta connection. 2 switch (SW2) 32. Furthermore, the induction motor control device of the present embodiment includes a step-up transformer (T) 18 that generates a boost voltage obtained by boosting the power supply voltage of the three-phase power source 36 for driving the induction motor (motor) 30, and the fourth switch 12. (SW4), a fifth switch (SW5) 20, a third switch 14 for selecting the power supply voltage or the boosted voltage so that the power supply voltage or the boosted voltage is applied to the three-phase coil, and a control circuit 22. The control circuit 22 applies the above-described boosted voltage after the power supply voltage is applied to the star-connected three-phase coil, and then applies the power supply voltage to the delta-connected three-phase coil. The switch (SW1) 34 to the third switch (SW3) 14 are controlled. Further, the step-up transformer (T) 18, the fourth switch (SW4) 12, and the fifth switch (SW5) 20 are voltages of the three-phase coil when the boost voltage is applied to the star-connected three-phase coil. Is higher than the voltage of the three-phase coil when the power supply voltage is applied to the star-connected three-phase coil and lower than the voltage of the three-phase coil when the power supply voltage is applied to the three-phase coil connected to the delta connection. The power supply voltage is boosted so that In the induction motor control device of the present embodiment, the aforementioned boosted voltage is applied after the power supply voltage is applied to the star-connected three-phase coil. Therefore, in this embodiment, the voltage of the three-phase coil is first about 58% of the power supply voltage. Then, the voltage of the three-phase coil becomes higher than about 58% of the power supply voltage and lower than 100% of the power supply voltage, and then becomes 100% of the power supply voltage. For this reason, the star delta can be switched smoothly as compared with the case where the voltage of the three-phase coil is changed from about 58% of the power supply voltage to 100% of the power supply voltage immediately. As a result, in the induction motor control device of the present embodiment, it is possible to suppress the occurrence of an inrush current when switching from the star connection to the delta connection. Furthermore, the induction motor control apparatus according to the present embodiment can be configured at low cost because an expensive resistor, an inverter, or the like is not required as in the techniques disclosed in Patent Documents 1 and 2.

In addition, the control circuit 22 of the present embodiment includes a timer that measures the time from when the power supply voltage is applied to the star-connected three-phase coil. When the timer times a predetermined time, for example, FIG. as shown in t _3, the boosted voltage is applied to the third switch (SW3) 14 off the three-phase coil. For this reason, the control circuit 22 can reliably accelerate the induction motor (motor) 30 when a predetermined time elapses after the power supply voltage is applied to the star-connected three-phase coil.

Further, the induction motor control device of the present embodiment is provided with a current detector 24 that detects the value of the current flowing through the three-phase coil of the induction motor 30. Then, the control circuit 22, when the current detected by the current detector 22 becomes equal to or higher than a constant current Im, for example, as shown in t ₃ in FIG. 3, in order to apply a boosted voltage to the three-phase coils are star-connected The third switch (SW3) 14 is turned off. For this reason, in the present embodiment, when the desired starting current (Im) is reached, the voltage of the three-phase coil is immediately increased, and the induction motor (motor) 30 can be accelerated.

In addition, the induction motor control device of the present embodiment is provided with a voltage detector 38 for detecting the voltage level of the three-phase power source 36. Then, the control circuit 22, when the voltage detected by the voltage detector 38, for example, the starting voltage V, as shown in t ₈ in FIG. 5, first in order to apply a boosted voltage to the three-phase coils are star-connected 3 switch (SW3) 14 is turned off. For this reason, in this embodiment, when the desired starting voltage V is reached, the voltage of the three-phase coil can be immediately increased, and the induction motor (motor) 30 can be accelerated.

In addition, the control circuit 22 of the present embodiment includes a timer that measures the time after the boosted voltage is applied to the star-connected three-phase coil. When the timer times a predetermined time, for example, FIG. as shown in t _4, the first switch (SW1) is turned off to turn on the second switch (SW2) and third switch (SW3) 14. That is, the control circuit 22 always changes the three-phase motor to the delta connection when a predetermined time elapses after the boosted voltage is applied to the star-connected three-phase coil. For this reason, in this embodiment, a three-phase motor can be reliably changed into a delta connection, and a 100% power supply voltage can be applied to a three-phase motor.

  In the present embodiment, the control circuit 22 includes a timer (first timer) for measuring the time after the power supply voltage is applied to the star-connected three-phase coil, and a booster for the star-connected three-phase coil. Although a timer (second timer) for measuring the time after the voltage is applied may be included, the present invention is not limited to this. For example, a configuration including only one of them may be used. Also, without providing different timers for the two timers, for example, the time after one power supply voltage is applied to the star-connected three-phase coil and the boosted voltage is applied to the star-connected three-phase coil It is good also as time-measurement after being done.

The induction motor control device according to the present embodiment is provided with a rotation speed detector 40 that detects the rotation speed of the induction motor (motor) 30. Then, the control circuit 22, the rotational speed detected by the rotational speed detector 40, for example, a N, as shown in t ₄ in FIG. 3, in order to change the three-phase motor from star connection to the delta connection, the The first switch (SW1) is turned off, and the second switch (SW2) and the third switch (SW3) 14 are turned on. For this reason, in this embodiment, when the induction motor (motor) 30 has a desired number of revolutions, the three-phase motor can be reliably changed to the delta connection, and a 100% power supply voltage can be applied to the three-phase motor.

  Further, a power supply voltage is applied to one end of the third switch (SW3) 14, and the other end is connected to a three-phase motor. A power supply voltage is applied to one end of the fourth switch (SW4) 12, and the other end is connected to a terminal on the input side of the step-up transformer (T) 18. An output-side terminal for generating a boosted voltage of the step-up transformer (T) 18 is connected to the other end of the third switch (SW3) 14. One end of the fifth switch (SW5) 20 is connected to a terminal different from the above-described two terminals among the three terminals of the step-up transformer (T) 18. The step-up transformer (T) 18 is supplied with the power supply voltage when the fourth switch (SW4) 12 is turned on, and boosts the power supply voltage when the fifth switch (SW5) 20 is turned on. As described above, in the present embodiment, the boosted voltage is generated using the booster transformer (T) 18. However, for example, a booster voltage higher than the power supply voltage may be generated using a general compound winding transformer. . However, by using the step-up transformer (T) 18 that is a single-winding transformer as in this embodiment, it is possible to reduce the cost and size of the induction motor control device, compared to the case of using a double-winding transformer.

  Further, in the present embodiment, for example, as shown in the process S44 of FIG. 4, before the power supply voltage is applied to the star-connected three-phase coil, a voltage lower than the power supply voltage is applied to the star-connected three-phase coil. The first switch (SW1) 34 and the fourth switch (SW4) 12 are turned on so that the second switch (SW2) 32, the third switch (SW3) 14, and the fifth switch (SW5) are applied. ) 20 is off. By putting such a process before the process (S50) of applying the power supply voltage to the star-connected three-phase coil, the voltage of the three-phase coil can be changed more gently. As a result, the rotation of the induction motor (motor) 30 can be gradually increased.

  Further, in this embodiment, when the boosted voltage is applied to the star-connected three-phase coil, the voltage of the three-phase coil (about 75%) is applied when the power supply voltage is applied to the star-connected three-phase coil. The three-phase coil voltage (about 58%) and the power supply voltage (100%) are boosted so that the power supply voltage is increased. For this reason, the change at the time of star connection and the change width of the voltage of the three-phase coil when shifting from the star connection to the delta connection are substantially the same, and the voltage of the three-phase coil can be changed gently.

  In addition, the said Example is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  For example, the control circuits 22, 210, and 280 are sequencers, but may be configured to include a microcomputer and a memory. In this case, the microcomputer executes the program stored in the memory, thereby executing the flowchart shown in FIG. 2, FIG. 5, or FIG. 8, and controlling the on / off of the switch.

  Further, for example, in the first embodiment, the voltage of the three-phase coil in three stages is changed from about 58% of the power supply voltage to, for example, 75% and 100%, in the star connection. is doing. For example, a step-up transformer, a switch, or the like that generates a boost voltage for setting the voltage of the star-connected three-phase coil to 90% of the power supply voltage, for example, may be provided separately from the step-up transformer (T) 18 and the like. good. Then, the control circuit 22 applies a boosted voltage at which the voltage of the three-phase coil becomes, for example, 75% of the power supply voltage to the star-formed three-phase coil, and then the voltage of the three-phase coil is higher than 75% of the power supply voltage. A boosted voltage lower than 100%, for example, 90%, may be applied to the three-phase coil. That is, by increasing the number of step-up transformers and the like, it is possible to change the voltage of the three-phase coil from 58% to 100% of the power supply voltage in finer steps. By setting it as such a structure, inrush current can be suppressed more.

10 Control device 12 4th switch (SW4)
14 Third switch (SW3)
16 Tap switch 18 Step-up transformer 20 Fifth switch (SW5)
22, 210, 280 Control circuit 24, 260 Current detector 30, 300 Induction motor (motor)
32 Delta connection second switch (SW2)
34 First switch for star connection (SWI)
36 Three-phase power supply 38,250 Voltage detector 40,270 Speed detector 100,500 Starter 110-112, 120-122, 130-132, 160-162, 170-172, 180-182 Switch 150-152 Coil 200 timer

Claims (22)

A first switch for star connection of the three-phase coil of the induction motor;
A second switch for delta connection of the three-phase coil;
A booster circuit for generating a boosted voltage obtained by boosting a power supply voltage of a power supply for driving the induction motor;
A third switch for selecting the power supply voltage or the boosted voltage so that the power supply voltage or the boosted voltage is applied to the three-phase coil;
The boosted voltage is applied after the power supply voltage is applied to the star-connected three-phase coil, and then the power supply voltage is applied to the three-phase coil that is delta-connected. A control circuit for controlling the switch;
With
The booster circuit includes:
The voltage of the three-phase coil when the boosted voltage is applied to the star-connected three-phase coil is the voltage of the three-phase coil when the power supply voltage is applied to the star-connected three-phase coil. Boosting the power supply voltage to be lower than the voltage of the three-phase coil when the power supply voltage is applied to the three-phase coil that is higher and delta-connected,
An induction motor control device characterized by the above. The induction motor control device according to claim 1,
The booster circuit includes:
A coil in which the power supply voltage is applied to a third terminal provided between the first terminal and the second terminal;
The third switch is
The fourth switch connected in series to the coil so that the boosted voltage is generated at the first terminal when turned on;
A fifth switch connected between the one terminal and the three-phase coil;
A sixth switch connected between the three-phase coil and a fourth terminal provided between the third terminal and the second terminal of the coil;
Including
The control circuit includes:
Turn on the first switch, the fifth switch, and the sixth switch among the first to sixth switches so that the power supply voltage is applied to the three-phase coil that is star-connected,
The sixth switch among the first switch, the fifth switch, and the sixth switch that are turned on is turned off so that the boosted voltage is applied to the three-phase coil that is star-connected. And turning on the fourth switch,
The first and fourth switches among the first switch, the fourth switch, and the fifth switch that are turned on so that the power supply voltage is applied to the three-phase coils that are delta-connected. And turning on the second and sixth switches,
An induction motor control device characterized by the above. The induction motor control device according to claim 2,
The control circuit includes:
After turning on the first and sixth switches among the first to sixth switches so that a voltage lower than the power supply voltage is applied to the star-connected three-phase coils, the three-phase coils that are star-connected Turning on the fifth switch in addition to the first and sixth switches being turned on so that the power supply voltage is applied to the phase coil;
An induction motor control device characterized by the above. The induction motor control device according to claim 3,
A timer for measuring a time from when the power supply voltage is applied to the third terminal;
The control circuit includes:
In addition to the first and sixth switches being turned on, the fifth switch is turned on so that the power supply voltage is applied to the star-connected three-phase coil when the timer counts a predetermined first time. Turning on,
An induction motor control device characterized by the above. The induction motor control device according to claim 4,
The control circuit includes:
The first switch that is turned on so that the boosted voltage is applied to the star-connected three-phase coil when the timer times a predetermined second time longer than the predetermined first time, Among the switch of 5 and the sixth switch, turning off the sixth switch and turning on the fourth switch;
An induction motor control device characterized by the above. The induction motor control device according to claim 5,
The control circuit includes:
The first switch that is turned on so that the power supply voltage is applied to the three-phase coil that is delta-connected when the timer measures a predetermined third time that is longer than the predetermined second time, Among the four switches and the fifth switch, turning off the first and fourth switches and turning on the second and sixth switches;
An induction motor control device characterized by the above. The induction motor control device according to claim 1,
The control circuit includes:
Including a first timer for measuring the time from when the power supply voltage is applied to the star-connected three-phase coil,
Controlling the third switch so that the boosted voltage is applied to the star-connected three-phase coil when the first timer measures a predetermined time;
An induction motor control device characterized by the above. The induction motor control device according to claim 1,
A current detector for detecting a current value flowing through the three-phase coil;
The control circuit includes:
When the power supply voltage is applied to the star-connected three-phase coil and the current value detected by the current detector becomes a predetermined value, the boosted voltage is applied to the star-connected three-phase coil. Controlling the third switch;
An induction motor control device characterized by the above. The induction motor control device according to claim 1,
A voltage detector for detecting a level of the power supply voltage;
The control circuit includes:
The boosted voltage is applied to the star-connected three-phase coil when the voltage level detected by the voltage detector reaches a predetermined level after the power supply voltage is applied to the star-connected three-phase coil. Controlling the third switch;
An induction motor control device characterized by the above. An induction motor control device according to claim 7,
The control circuit includes:
A second timer for measuring the time from when the boosted voltage is applied to the star-connected three-phase coil;
The control circuit includes:
Controlling the first to third switches so that the power supply voltage is applied to the three-phase coils connected in delta when the second timer times a predetermined time;
An induction motor control device characterized by the above. The induction motor control device according to claim 8 or 9, wherein
The control circuit includes:
Including a timer for measuring the time after the boosted voltage is applied to the three-phase coil connected in a star connection;
Controlling the first to third switches so that the power supply voltage is applied to the three-phase coils connected in delta when the timer counts a predetermined time;
An induction motor control device characterized by the above. An induction motor control device according to claim 7-9,
A rotation speed detector for detecting the rotation speed of the induction motor;
The control circuit includes:
When the boosted voltage is applied to the star-connected three-phase coil and the rotational speed detected by the rotational speed detector reaches a predetermined rotational speed, the power supply voltage is applied to the delta-connected three-phase coil. Controlling the first to third switches to be
An induction motor control device characterized by the above. The induction motor control device according to claim 1,
The third switch is
The power supply voltage is applied to one end, the other end is connected to the three-phase motor,
The booster circuit includes:
A fourth switch to which the power supply voltage is applied at one end;
A single-winding transformer in which the other end of the fourth switch is connected to the first terminal and the other end of the third switch is connected to the second terminal;
A fifth switch having one end connected to the third terminal of the single-winding transformer, so that when the single-turn transformer is turned on, the voltage of the first terminal can be boosted and output from the second terminal;
Including
The single-winding transformer is
When the fourth and fifth switches are turned on, the boosted voltage is output from the second terminal,
The control circuit includes:
The first to fifth switches are applied so that the boosted voltage is applied after the power supply voltage is applied to the star-connected three-phase coil, and the power supply voltage is further applied to the three-phase coil connected in delta connection. Controlling,
An induction motor control device characterized by the above. An induction motor control device according to claim 13,
The control circuit includes:
Before the power supply voltage is applied to the star-connected three-phase coil, the first and fourth switches are turned on so that a voltage lower than the power supply voltage is applied to the star-connected three-phase coil, Turning off the second, third, and fifth switches;
An induction motor control device characterized by the above. The induction motor control device according to claim 1,
The booster circuit includes:
The voltage of the three-phase coil when the boosted voltage is applied to the star-connected three-phase coil is the voltage of the three-phase coil when the power supply voltage is applied to the star-connected three-phase coil. And boosting the power supply voltage to be an intermediate voltage between the power supply voltage,
An induction motor control device characterized by the above. In the induction motor control method for switching and controlling the coil in the induction motor connected to the three-phase power source between star connection and delta connection,
In the star connection state of the induction motor coil, an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state is applied to the induction motor coil, and the induction motor rotates at a constant rotational speed. The induction motor control is characterized in that when the state reaches the state of stopping, the application of the intermediate voltage is stopped and the switching to the delta connection is performed, and the induction motor is accelerated in the star connection state and then switched to the delta connection. Method.   The intermediate voltage between the coil voltage in the star connection state and the coil voltage in the delta connection state is applied in a state where the current of the induction motor coil becomes a constant value after the star connection. Item 17. The induction motor control method according to Item 16.   Generation of an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state is performed by a step-up transformer, and the connection of the three-phase power source to the induction motor coil at the time of starting the induction motor, A part of the step-up transformer is operated as a reactor through a part of the step-up transformer, and after the voltage drop of the three-phase power supply is recovered, the intermediate voltage is applied to the induction motor coil. The induction motor control method according to claim 17. Switching between an induction motor connected to a three-phase power source, a first switch having a star connection for a coil of the induction motor and a second switch having a delta connection, and the first switch and the second switch; In the induction motor control device having the control means for starting the induction motor with star connection and driving with delta connection,
Booster that is provided corresponding to each phase of the three-phase power source and applies a voltage that is an intermediate voltage between the voltage of the coil in the star connection state and the voltage of the coil in the delta connection state to the coil in the star connection state A state in which the voltage boosted by the step-up transformer is applied to a corresponding coil of the induction motor in a star connection state by the transformer and the first switch, and the induction motor has reached a rated rotational speed in the star connection And a plurality of switch groups for separating the step-up transformer, and the control means controls the switch group to apply a voltage boosted by the step-up transformer in a star connection state to the induction motor coil, Disconnect the step-up transformer while the motor is rotating at a constant rotational speed, and connect the delta connection with the twelfth switch. Induction motor control device and controls so as to shift to state.   The plurality of switch groups include a third switch connected between each phase of the three-phase power source and a corresponding coil of the induction motor, one end on the primary side of each step-up transformer, and the three-phase power source. A fourth switch provided between each phase of the step-up transformer and a fifth switch connected between the coupling point of the other primary side ends of the respective step-up transformers and the other end of the primary side 20. The induction motor control device according to claim 19, wherein a step-up side of the step-up transformer is connected between the third switch and the induction motor coil.   A detecting means for detecting a current flowing in the induction motor coil; and a detecting means for detecting the number of revolutions of the induction motor. The control means is a star-connected state by the first switch, and the induction motor current from the current detecting means is constant. In response to the signal reaching the value state, the voltage boosted by the step-up transformer is applied to the induction motor coil, and the induction motor rotation speed detection means from the induction motor rotation speed detection means receives the signal reaching the constant value state. The switch group is configured to control ON / OFF so as to stop application of the boost voltage from the boost transformer to the induction motor coil and shift to the delta connection state by the second switch. The induction motor control device according to claim 20.   The three-phase power supply voltage detection means, the control means in the star connection state by the first switch accompanying the start of the induction motor, the three-phase power supply via the part of the step-up transformer Connected to the induction motor coil, received a voltage drop recovery signal of the three-phase power supply by the voltage detection means, stopped part of the step-up transformer and directly connected the three-phase power supply to the induction motor coil, ON / OFF of the switch group is controlled so as to shift to a state in which a voltage boosted by the step-up transformer is applied to the induction motor coil in response to a re-restoration signal of the voltage drop of the three-phase power supply by the voltage detecting means. The induction motor control device according to claim 21, wherein the induction motor control device is configured as described above.

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