WO2011061866A1 - Induction motor control apparatus - Google Patents

Abstract

Disclosed is an induction motor control apparatus provided with: a step-down circuit comprising first coils having taps that are connected to three phase coils of an induction motor, first switches connected between a power supply for driving the induction motor and the first coils, and second switches connected to the first coils at the side that does not have the first switches connected; third switches connected between the power supply and the three phase coils; and a first control circuit that controls the first to third switches so as to have the first and second switches switched on after switching on the first switches, and have the power supply voltage applied to the three phase coils thereafter. The taps are installed so that the voltage at the taps when the first and second switches are switched on is higher than the tap voltage when the first switch is switched on.

Description

Induction motor controller

The present invention relates to an induction motor control device.

As a method of starting the induction motor, for example, there is a condorfa start (see, for example, JP-A-2001-218486). A starter that starts the induction motor with a condor system first applies a power supply voltage to the induction motor after applying a voltage lower than the power supply voltage of the induction motor. In this way, by changing the voltage applied to the induction motor, for example, the starting current can be suppressed as compared with the case where the induction motor is started by directly applying the power supply voltage to the induction motor.

<Cross-reference of related applications>
This application claims priority based on Japanese Patent Application No. 2009-264172 filed on November 19, 2009, the contents of which are incorporated herein by reference.

Incidentally, the level of the initial voltage first applied to the induction motor when the induction motor is started with a condorfa is generally preset in the starter. For example, when the initial voltage level is set low, the starting current can be reduced. However, in this case, since the difference between the initial voltage and the power supply voltage becomes large, when the power supply voltage is applied, the rotation speed of the induction motor changes abruptly.
On the other hand, when the initial voltage level is set high, the difference between the initial voltage and the power supply voltage becomes small, so that the change in the rotation speed of the induction motor when the power supply voltage is applied becomes moderate. However, in this case, the starting current increases because the level of the initial voltage is high.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an induction motor control device that can gently change the number of revolutions of the induction motor while suppressing the starting current.

In order to achieve the above object, an induction motor control apparatus according to one aspect of the present invention includes a first coil having a tap connected to a three-phase coil of an induction motor, a power source for driving the induction motor, and the A first switch connected between the first coil and a second switch connected to a side of the first coil to which the first switch is not connected, wherein the first and second switches are The step-down circuit that generates a voltage obtained by stepping down the power source voltage of the power source by being controlled, the third switch connected between the power source and the three-phase coil, and the first switch turned on A first control circuit that turns on the first and second switches later, and then controls the first to third switches so that the power supply voltage is applied to the three-phase coil, and the tap includes: Voltage of the tap when the serial first switch and the second switch is turned on, the first switch is provided so as to be higher than the voltage of the tap when it is turned on.

It is a figure which shows the structure of the starter 10 which is one Embodiment of this invention. 3 is a diagram illustrating an example of a coil 70. FIG. 3 is a flowchart for explaining the operation of the starter 10; It is a figure which shows the structure of the starter 11 which is one Embodiment of this invention. It is a figure which shows the structure of the starter 12 which is one Embodiment of this invention. It is a figure which shows the structure of 46 A of magnetic circuits. It is a figure for demonstrating the detail of the switch 90 and the coil 95. FIG. It is a figure which shows the structure of the magnetic circuit 46B. 3 is a diagram for explaining details of a switch 100 and a coil 110. FIG. 3 is a flowchart for explaining the operation of the starter 12; It is a figure which shows the structure of the starter 13 which is one Embodiment of this invention.

At least the following matters will become clear from the description of this specification and the accompanying drawings.

== First embodiment of the starter ==
First, the structure of the starter which is one Embodiment of this invention is demonstrated. FIG. 1 is a diagram illustrating a configuration of a starter 10 that is the first embodiment of the starter. The starter 10 (induction motor control device) is a device for receiving a voltage of a three-phase power supply and starting a squirrel-cage induction motor (hereinafter simply referred to as a motor) 15, and includes a step-down circuit 20-22, a switch 30 to 32, a timer 40, and a control circuit 41.

The motor 15 is a three-phase motor in which three-phase coils L1 to L3 are delta-connected. In this embodiment, the node to which the three-phase coil L1 and the three-phase coil L3 are connected is the node A, the node to which the three-phase coil L2 and the three-phase coil L1 are connected is the node B, and the three-phase coil L3 is A node to which the three-phase coil L2 is connected is referred to as a node C.

The step-down circuit 20 is a circuit that generates a voltage obtained by stepping down the U-phase voltage Vu of the three-phase power source at the tap t0, and includes a switch 60, a coil 70, and a switch 80.

The switch 60 is a relay switch that is turned on / off based on the control of the control circuit 41, and a voltage Vu is applied to one end.

The coil 70 has a tap t0 connected to the node A, and is connected between the switch 60 and the switch 80. The coil 70 is wound around an iron core 200 of a single-winding transformer as shown in FIG.

The switch 80 is a relay switch that is turned on and off based on the control of the control circuit 41, similarly to the switch 60. One end of the switch 80 is connected to the coil 70, and the other end is connected to the switches 81 and 82. Therefore, although the details will be described later, when the switches 80 to 82 are turned on, the coils 70 to 72 are star-connected, and the node to which each of the switches 80 to 82 is connected becomes a so-called neutral point.

The step-down circuit 21 is a circuit that generates a voltage obtained by stepping down the V-phase voltage Vv of the three-phase power source at the tap t1, and includes a switch 61, a coil 71, and a switch 81. The step-down circuit 22 is a circuit that generates a voltage obtained by stepping down the W-phase voltage Vw of the three-phase power supply at the tap t2, and includes a switch 62, a coil 72, and a switch 82. The step-down circuit 21 has the same configuration as the step-down circuit 20 except that the tap t1 is connected to the node B. The step-down circuit 22 has the same configuration as the step-down circuit 20 except that the tap t2 is connected to the node C. Therefore, a detailed description of the step-down circuits 21 and 22 is omitted.

The switch 30 is a relay switch for applying the voltage Vu to the node A, and is controlled to be turned on and off by the control circuit 41. The switch 31 is a relay switch for applying the voltage Vv to the node B, and is turned on and off by the control circuit 41. The switch 32 is a relay switch for applying the voltage Vw to the node C, and is turned on and off by the control circuit 41.

The timer 40 measures the time from when the switches 60 to 62 are turned on.

The control circuit 41 (first control circuit) is a sequencer that controls the switches 30 to 32, 60 to 62, and 80 to 82 at a predetermined timing when a start signal for starting the motor 15 is input. Specifically, the control circuit 41 turns on the switches 60 to 62 (first switch) when a start signal is input. Thereafter, when the time counted by the timer 40 reaches a predetermined time T1, the control circuit 41 turns on the switches 80 to 82 (second switch) together with the switches 60 to 62. When the time measured by the timer 40 reaches a predetermined time T2 (> T1), the control circuit 41 turns off the switches 80 to 82 and then turns on the switches 30 to 32 (third switch), and then switches 60 -62 is turned off. Note that a series of control for the switch of the control circuit 41 at time T2 is executed in a sufficiently short time. The start signal is provided, for example, in an operation unit (not shown) of the starter 10 and is generated when a user turns on a start switch (not shown) for starting the motor 15. The coils 70 to 72 correspond to the first coil.

== Operation of Starter 10 ==
Here, operation | movement of the starter 10 is demonstrated, referring 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 10 are turned off.

First, when a user turns on a start switch (not shown), a start signal is input to the control circuit 41 (S100). As a result, the control circuit 41 turns on the switches 60 to 62 (S101). By the way, a part of the winding of the coil 70 exists from the node where the switch 60 and the coil 70 are connected to the tap t0. Therefore, when the switch 60 is turned on, a current corresponding to the voltage Vu is supplied to the node A through a part of the winding of the coil 70 described above. The same applies to the current supplied to the nodes B and C when the switches 61 and 62 are turned on. For this reason, when the switches 60 to 62 are turned on in the process 101, so-called reactor start of the motor 15 is executed.

As described above, when the switches 60 to 62 are turned on, the timer 40 starts measuring time. When the time measured by the timer 40 reaches time T1 (S102: YES), the control circuit 41 turns on the switches 80 to 82 together with the switches 60 to 62 (S103). When the switches 60 to 62 and 80 to 82 are turned on, the coils 70 to 72 are star-connected. Therefore, when the switches 60 to 62 and 80 to 82 are on, each of the step-down circuits 20 to 22 operates as a circuit for starting the motor 15 with a condor.

Here, in the present embodiment, when the motor 15 is reactor-started (processing: S101), the voltage at the taps t0 to t2 is, for example, 50% of the power supply voltage, and when the motor 15 is starting the condorfa (processing) : The positions of the taps t0 to t2 are determined so that the voltage of the taps t0 to t2 in S103) is, for example, 70% of the power supply voltage. For this reason, in the present embodiment, when the condor is started after the reactor 15 is started, the voltages of the three-phase coils L1 to L3 of the motor 15 are increased, and the rotational speed of the motor 15 is increased.

When the time counted by the timer 40 reaches time T2 (S104: YES), the control circuit 41 sequentially turns off the switches 80 to 82, turns on the switches 30 to 32, and turns off the switches 60 to 62 ( S105). As a result, the voltages Vu, Vv, and Vw are applied to the nodes A, B, and C, respectively, and the motor 15 is driven with the power supply voltage.

Thus, by using the starter 10, the motor 15 is started by the reactor start and accelerated by the condorfa start. Furthermore, the motor 15 is normally operated by applying a power supply voltage. Further, since the voltages of the three-phase coils L1 to L3 sequentially change to 50%, 70%, and 100% of the power supply voltage, the starter 10 smoothly executes acceleration of the motor 15 while suppressing the starting current. It becomes possible.

== Second embodiment of the starter ==
FIG. 4 is a diagram illustrating a configuration of a starter 11 that is the second embodiment of the starter. The starter 11 (induction motor controller) includes step-down circuits 20 to 22, switches 30 to 32, a timer 40, a voltage detector 42, a current detector 43, a rotation speed detector 44, and a control circuit 45. The In the starter 11, the same reference numerals as those of the starter 10 shown in FIG. 1 are the same. Therefore, here, the voltage detector 42, the current detector 43, and the rotation speed detector 44, which are blocks added to the starter 10, and the control circuit 45 changed from the control circuit 41 of the starter 10, Will be described.

The voltage detector 42 detects the levels of the voltages Vu, Vv, and Vw and outputs voltage signals indicating the respective levels to the control circuit 45.

The current detector 43 detects the currents Ia, Ib, and Ic supplied to the nodes A, B, and C, and outputs current signals indicating the respective current values to the control circuit 45.

The rotation speed detector 44 detects the rotation speed of the motor 15 and outputs a rotation speed signal indicating the rotation speed to the control circuit 45.

The control circuit 45 (first control circuit) is a sequencer that controls the switches 30 to 32, 60 to 62, and 80 to 82 under a predetermined condition when a start signal for starting the motor 15 is input.

Specifically, the control circuit 45 turns on the switches 60 to 62 when a start signal is input. Thereafter, the control circuit 45 determines whether the time measured by the timer 40 reaches a predetermined time T1, the levels of the voltages Vu, Vv, Vw become the predetermined voltage V1, or the current values of the currents Ia, Ib, Ic are predetermined. When the current value I1 or the rotational speed of the motor 15 reaches a predetermined rotational speed N1, the switches 80 to 82 are turned on together with the switches 60 to 62. Here, Condition 1 is a condition that must be satisfied when the control circuit 45 turns on the switches 80 to 82 together with the switches 60 to 62.

Then, the control circuit 45 determines whether the time measured by the timer 40 is a predetermined time T2 (> T1), the levels of the voltages Vu, Vv, Vw are the predetermined voltage V2, or the currents Ia, Ib, Ic. When the current value reaches the predetermined current value I2 or the rotational speed of the motor 15 reaches the predetermined rotational speed N2 (> N1), the switches 30 to 32 are turned on after the switches 80 to 82 are turned off, and then the switch 60 is turned on. -62 is turned off. Here, Condition 2 is a condition that should be satisfied when the control circuit 45 turns off the switches 80 to 82. Further, a series of control for the switch of the control circuit 45 when the condition 2 is satisfied is executed in a sufficiently short time.

Such a starter 11 operates in the same manner as the starter 10 shown in FIG. Specifically, when a start signal is input, the motor 15 is reactor-started. When the condition 1 is satisfied, the motor 15 is started by a condor. Thereafter, when the condition 2 is satisfied, the motor 15 is driven with the power supply voltage.

== Third embodiment of starter ==
FIG. 5 is a diagram showing a configuration of a starter 12 which is the third embodiment of the starter. The starter 12 (induction motor controller) includes step-down circuits 25 to 27, switches 30 to 32, a timer 40, a magnetic circuit 46, and a control circuit 47. In the starter 12, the same reference numerals as those of the starter 10 shown in FIG. Therefore, here, the step-down circuits 25 to 27, the magnetic circuit 46A, and the control circuit 47 will be described.

The step-down circuit 25 is a circuit that generates a voltage obtained by stepping down the voltage Vu at the tap t0, and includes a switch 60, coils 70 and 75, and a switch 80. In the step-down circuit 25, a coil 75 is connected between the switch 60 and the coil 70 described above. The coil 75 is an element for increasing inductive reactance from the switch 60 to the tap t0.

The step-down circuit 26 is a circuit that generates a voltage obtained by stepping down the voltage Vv at the tap t1, and includes a switch 61, coils 71 and 76, and a switch 81. The step-down circuit 27 is a circuit that generates a voltage obtained by stepping down the voltage Vw at the tap t2, and includes a switch 62, coils 72 and 77, and a switch 82. Since the step-down circuits 26 and 27 have the same configuration as that of the step-down circuit 25, a detailed description is omitted here. The coils 75 to 77 correspond to the second coil.

The magnetic circuit 46 is a circuit that reduces the magnetic fields of the coils 75 to 77 based on the control from the control circuit 47.

== First Embodiment of Magnetic Circuit ==
A magnetic circuit 46A, which is a first embodiment of the magnetic circuit 46, includes switches 90 to 92 (fourth switch) and coils 95 to 97 (third coil) as shown in FIG. Here, for example, details of the switch 90 and the coil 95 will be described with reference to FIG. In the present embodiment, the coils 75 and 95 are wound around the iron core 210, and the coil 70 is wound around the iron core 220. Further, it is assumed that the coil 75 is wound around the iron core 210 so as to generate a magnetic field in a downward direction on the paper surface when the switch 60 is turned on and a current is supplied.

The switch 90 is a relay switch that is turned on / off based on the control of the control circuit 47, and is connected between the coil 75 and the coil 95.

The coil 95 has one end connected to one end of the switch 60 and the coil 75, and the other end connected to the other end of the coil 70 and the coil 75 via the switch 90. The coil 95 is wound around the iron core 210 so as to generate a magnetic field in the upward direction on the paper surface when the switch 60 and the switch 90 are turned on and a current is supplied. That is, when the switch 60 is turned on, the coil 75 generates a magnetic field in the downward direction on the paper surface. However, when the switch 90 is further turned on, the coil 95 generates a magnetic field in the upward direction on the paper surface, and thus the magnetic field generated by the coil 75 decreases. It will be. In the present embodiment, the number of turns of the coil 95 is determined so that the magnetic field of the iron core 210 becomes zero when the switches 60 and 90 are turned on. For this reason, when the switches 60 and 90 are turned on, the inductive reactance of the coil 75 becomes negligibly small.

The switch 91 and the coil 96 have the same configuration as the switch 90 and the coil 95, and the coil 96 is wound around the same iron core (not shown) so as to cancel the magnetic field of the coil 76. For this reason, when the switches 61 and 91 are turned on, the inductive reactance of the coil 76 can be ignored.

The switch 92 and the coil 97 have the same configuration as the switch 90 and the coil 95, and the coil 97 is wound around the same iron core (not shown) so as to cancel the magnetic field of the coil 77. For this reason, when the switches 62 and 92 are turned on, the inductive reactance of the coil 77 can be ignored.

== Second Embodiment of Magnetic Circuit ==
A magnetic circuit 46B, which is a second embodiment of the magnetic circuit 46, includes switches 100 to 102 (fourth switch) and coils 110 to 112 (third coil) as shown in FIG. Here, for example, details of the switch 100 and the coil 110 will be described with reference to FIG.

In this embodiment, the coils 75 and 110 are wound around the iron core 250, and the coil 70 is wound around the iron core 260.

The switch 100 is a relay switch that is turned on / off based on the control of the control circuit 47, and is connected between both ends of the coil 110.

The coil 110 is wound around the same iron core 250 as the coil 75. Therefore, when a magnetic field is generated in the iron core 250 while the switch 100 is on, a current that decreases the magnetic field of the iron core 250 flows through the coil 110. On the other hand, when the switch 100 is off, no current flows through the coil 110, so the magnetic field of the iron core 250 is not affected by the coil 110. In the present embodiment, it is assumed that the number of turns of the coil 110 is determined so that the magnetic field of the iron core 250 becomes zero when the switches 60 and 100 are turned on. For this reason, when the switches 60 and 110 are turned on, the inductive reactance of the coil 75 becomes negligibly small.

The switch 101 and the coil 111 have the same configuration as the switch 100 and the coil 110, and the coil 111 is wound around the same iron core (not shown) so as to cancel the magnetic field of the coil 76. For this reason, when the switches 61 and 101 are turned on, the inductive reactance of the coil 76 can be ignored.

The switch 102 and the coil 112 have the same configuration as the switch 100 and the coil 110, and the coil 112 is wound around the same iron core (not shown) so as to cancel the magnetic field of the coil 77. For this reason, when the switches 62 and 102 are turned on, the inductive reactance of the coil 77 can be ignored.

== Details of Control Circuit 47 ==
When the start signal for starting the motor 15 is input, the control circuit 47 (first and second control circuits) in FIG. 5 switches the switches 30 to 32, 60 to 62, 80 to 82, at a predetermined timing. This is a sequencer for controlling 90 to 92 (or 100 to 102). Specifically, the control circuit 47 turns on the switches 60 to 62 when a start signal is input. Thereafter, when the time measured by the timer 40 reaches a predetermined time T1, the control circuit 41 turns on the switches 80 to 82 and 90 to 92 (or 100 to 102) together with the switches 60 to 62. When the time counted by the timer 40 reaches a predetermined time T2 (> T1), the control circuit 47 turns off the switches 80 to 82 and 90 to 92 (or 100 to 102) and then turns on the switches 30 to 32. Thereafter, the switches 60 to 62 are turned off. Note that a series of control for the switch of the control circuit 47 at time T2 is executed in a sufficiently short time.

== Operation of Starter 12 ==
Here, the operation of the starter 12 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 12 are turned off. Furthermore, it is assumed here that a magnetic circuit 46A is used as the magnetic circuit.

First, when a user turns on a start switch (not shown), a start signal is input to the control circuit 47 (S200). As a result, the control circuit 47 turns on the switches 60 to 62 (S201). When the switch 60 is turned on, a current corresponding to the voltage Vu is supplied to the node A via the coil 75 and a part of the winding of the coil 70. The same applies to the current supplied to the nodes B and C when the switches 61 and 62 are turned on. Therefore, when the switches 60 to 62 are turned on in the process 201, so-called reactor start of the motor 15 is executed.

In addition, when the switches 60 to 62 are turned on, the timer 40 starts measuring time. When the time measured by the timer 40 reaches time T1 (S202: YES), the control circuit 47 turns on the switches 80 to 82 and 90 to 92 together with the switches 60 to 62 (S203). When the switches 60 to 62 and 80 to 82 are turned on, the coils 70 to 72 and 75 to 77 are star-connected. However, when the switches 90 to 92 are turned on, the inductive reactance of the coils 75 to 77 is sufficiently small as described above, so that the influence of the coils 75 to 77 can be ignored. Therefore, for example, in the step-down circuit 25, depending on the ratio of a part of the winding of the coil 70 existing from the node where the coil 75 and the coil 70 are connected to the tap t0 to the winding of the remaining coil 70. Voltage is generated at tap t0. The step-down circuits 26 and 27 operate in the same manner as the step-down circuit 25, and the motor 15 is started by a condor.

Here, in the present embodiment, the positions of the taps t0 to t2 are determined so that the voltage at the taps t0 to t2 when the motor 15 is started with the condorfa (process: S203) is, for example, 70% of the power supply voltage. ing. Furthermore, the inductances of the coils 75 to 77 are determined so that the voltage at the taps t0 to t2 when the motor 15 is being reactor-started (process: S201) is, for example, 50% of the power supply voltage. For this reason, in the present embodiment, when the condor is started after the reactor 15 is started, the voltages of the three-phase coils L1 to L3 of the motor 15 are increased, and the rotational speed of the motor 15 is increased.

When the time counted by the timer 40 reaches time T2 (S204: YES), the control circuit 47 sequentially turns off the switches 80 to 82 and 90 to 92, turns on the switches 30 to 32, and switches 60 to 62. Is turned off (S105). As a result, the voltages Vu, Vv, and Vw are applied to the nodes A, B, and C, respectively, and the motor 15 is driven with the power supply voltage.

Thus, by using the starter 12, the motor 15 is started by the reactor start and accelerated by the condorfa start. Furthermore, the motor 15 is normally operated by applying a power supply voltage. Further, since the voltages of the three-phase coils L1 to L3 sequentially change to 50%, 70%, and 100% of the power supply voltage, the starter 12 smoothly accelerates the motor 15 while suppressing the starting current. It becomes possible.

Note that although the magnetic circuit 46A is used here, the starter 12 operates in the same manner even when the magnetic circuit 46B is used.

== Fourth embodiment of the starter ==
FIG. 11 is a diagram illustrating a configuration of a starter 13 that is the fourth embodiment of the starter. The starter 13 (induction motor controller) includes step-down circuits 25 to 27, switches 30 to 32, a timer 40, a voltage detector 42, a current detector 43, a rotation speed detector 44, a magnetic circuit 46A, and a control circuit 48. Consists of including. In the starter 13, the same reference numerals as those of the starters 11 and 12 are the same. Therefore, here, the control circuit 48 will be described.

When a start signal for starting the motor 15 is input, the control circuit 48 (first and second control circuits) switches 30 to 32, 60 to 62, 80 to 82, 90 to 92 under predetermined conditions. It is a sequencer that controls.

Specifically, the control circuit 48 turns on the switches 60 to 62 when a start signal is input. Thereafter, the control circuit 48 determines whether the time measured by the timer 40 reaches the predetermined time T1, the levels of the voltages Vu, Vv, Vw become the predetermined voltage V1, or the current values of the currents Ia, Ib, Ic are predetermined. When the current value I1 or the rotational speed of the motor 15 reaches a predetermined rotational speed N1, the switches 80 to 82 and 90 to 92 are turned on together with the switches 60 to 62. Here, a condition to be satisfied when the control circuit 45 turns on the switches 80 to 82 and 90 to 92 together with the switches 60 to 62 is defined as a condition A.

Then, the control circuit 48 determines whether the time measured by the timer 40 is a predetermined time T2 (> T1), the levels of the voltages Vu, Vv, Vw are the predetermined voltage V2, or the currents Ia, Ib, Ic. When the current value reaches a predetermined current value I2 or the rotational speed of the motor 15 reaches a predetermined rotational speed N2 (> N1), the switches 80 to 82 and 90 to 92 are turned off, and then the switches 30 to 32 are turned on. Thereafter, the switches 60 to 62 are turned off. Here, a condition to be satisfied when the control circuit 45 turns off the switches 80 to 82 and the like is defined as a condition B. Further, a series of control for the switch of the control circuit 45 when the condition B is satisfied is executed in a sufficiently short time.

Such a starter 13 operates in the same manner as the starter 12 shown in FIG. Specifically, when a start signal is input, the motor 15 is reactor-started. When the condition A is satisfied, the motor 15 is started with a condor. Thereafter, when the condition B is satisfied, the motor 15 is driven with the power supply voltage.

The starters 10 to 13 that are one embodiment of the present invention have been described above. The starters 10 to 13 start the condorfa after starting the reactor of the motor 15. After that, the starters 10 to 13 drive the motor 15 with the power supply voltage. In the taps t0 to t2 of the present embodiment, the voltages at the taps t0 to t2 when the motor 15 is started by the reactor are, for example, 50% of the power supply voltage, and the taps t0 to t2 when the motor 15 is started by the condorfa Is set to 70% of the power supply voltage, for example. For this reason, in this embodiment, the voltages of the three-phase coils L1 to L3 of the motor 15 increase in three stages, 50%, 70%, and 100% of the power supply voltage. Therefore, for example, in this embodiment, the motor current is suppressed while suppressing the starting current of the three-phase coils L1 to L3 as compared with the case of the general condorfa starting in which the voltages of the three-phase coils L1 to L3 are changed in two stages. The number of revolutions of 15 can be increased gently. 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. The step-down circuits 20 to 22 are the same as circuits generally used when starting a condorfa. However, in this embodiment, the reactor 15 of the motor 15 can be started by providing a period during which the switches 60 to 62 are turned on first. For this reason, in this embodiment, an additional component is not needed with respect to the circuit at the time of a general condor start, and the increase in cost can also be suppressed.

In this embodiment, the switches 80 to 82 are turned off before the switches 30 to 32 are turned on. Therefore, when the switches 30 to 32 are turned on, the current returning from the three-phase power source to the three-phase power source through the switches 30 to 32, the taps t0 to t2, the switches 80 to 82, and the neutral point is surely cut off. can do.

In the starters 12 and 13 of the present embodiment, coils 75 to 77 are connected between the switches 60 to 62 and the coils 70 to 72. The magnetic circuits 46A and 46B reduce the magnetic field of the coils 75 to 77 so that the inductive reactance of the coils 75 to 77 can be ignored when the motor 15 is started by the condor. For this reason, the voltages at the taps t0 to t2 when the motor 15 is started by the condorfa are freely determined based on the positions of the taps t0 to t2. Further, the voltage at the taps t0 to t2 when the motor 15 is being reactor started can be freely determined by changing the inductance of the coils 75 to 77. Therefore, the starters 12 and 13 are tapped more freely than the starters 10 and 11 that adjust the voltage at the start of the reactor and the condorfa by changing only the position of the taps t0 to t2, for example. The voltage from t0 to t2 can be adjusted.

In the magnetic circuit 46A, the coil 95 is connected in parallel to the coil 75 so that the magnetic field of the coil 75 is reduced when the switch 90 is turned on. By using the magnetic circuit having such a configuration, the magnetic field of the coil 75 can be reliably reduced. In order to make the inductive reactance of the coil 75 negligible, for example, a relay switch (not shown) that can short-circuit both ends of the coil 75 may be provided. However, since a large current flows through a relay switch that shorts both ends of the coil 75, a load is applied to the contact point of the relay switch. Since the coil 90 is connected in series to the switch 90 of this embodiment, the above-described problem does not occur.

The magnetic circuit 46B is provided with a coil 110 that is magnetically coupled to the coil 75 and reduces the magnetic field of the coil 75 when the switch 100 is turned on. By using the magnetic circuit having such a configuration, the magnetic field of the coil 75 can be reliably reduced. In addition, the switch 100 does not flow a large current generated when both ends of the coil 75 as described above are short-circuited. For this reason, it becomes possible to prevent the contact of the switch 100 from deteriorating. Further, the switch 100 is electrically insulated from the step-down circuit 25. For this reason, for example, even if the voltage Vu or the like is a high voltage, the switch 100 can be turned on / off at a voltage sufficiently lower than the voltage Vu.

In addition, the starters 10 and 11 are provided with a timer 40 that measures the time from when the switches 60 to 62 are turned on. When the timer 40 measures the time T1, the control circuits 41 and 45 turn on the switches 60 to 62 and 80 to 82 to start the motor 15 with a condor. Therefore, the starters 10 and 11 can reliably accelerate the motor 15 when a predetermined time elapses after the switches 60 to 62 are turned on.

Further, the starter 11 is provided with a rotation speed detector 44 for detecting the rotation speed of the motor 15. Then, when the rotational speed detected by the rotational speed detector 44 becomes N1, for example, the control circuit 45 turns on the switches 60 to 62 and 80 to 82 to start the motor 15 with a condor. For this reason, the starter 11 can reliably accelerate the motor 15 when the motor 15 reaches a desired rotational speed.

Further, the starter 11 is provided with a current detector 43 that detects the value of the current flowing through the three-phase coils L1 to L3. Then, when the current detected by the current detector 43 becomes, for example, I1, the control circuit 45 turns on the switches 60 to 62 and 80 to 82 to start the motor 15 with a condor. Therefore, the starter 11 can reliably accelerate the motor 15 when the current value flowing through the three-phase coils L1 to L3 reaches a desired value.

Further, the starter 11 is provided with a voltage detector 42 for detecting the voltage levels of the voltages Vu, Vv, and Vw. When the voltage detected by the voltage detector 42 becomes, for example, the voltage V1, the control circuit 45 turns on the switches 60 to 62 and 80 to 82 to start the motor 15 with a condor. Therefore, the starter 11 can reliably accelerate the motor 15 when the voltage levels of the voltages Vu, Vv, and Vw reach desired values.

In addition, the starters 12 and 13 are provided with a timer 40 that measures the time from when the switches 60 to 62 are turned on. When the timer 40 measures the time T1, the control circuits 47 and 48 turn on the switches 60 to 62 and 80 to 82, and further control the magnetic circuits 46A and 46B so that the magnetic fields of the coils 75 to 77 are reduced. Therefore, the starters 10 and 11 can reliably accelerate the motor 15 at a desired voltage when a predetermined time has elapsed after the switches 60 to 62 are turned on.

Further, the starter 13 is provided with a rotation speed detector 44 for detecting the rotation speed of the motor 15. Then, the control circuit 48 turns on the switches 60 to 62 and 80 to 82 when the rotation speed detected by the rotation speed detector 44 becomes N1, for example, and further magnetically reduces the magnetic fields of the coils 75 to 77. The circuit 46A is controlled. For this reason, the starter 11 can reliably accelerate the motor 15 at a desired voltage when the motor 15 reaches a desired rotational speed.

Further, the starter 13 is provided with a current detector 43 for detecting the current value flowing through the three-phase coils L1 to L3. Then, when the current detected by the current detector 43 becomes I1, for example, the control circuit 48 turns on the switches 60 to 62 and 80 to 82, and further sets the magnetic circuit 46A so that the magnetic fields of the coils 75 to 77 are reduced. Control. Therefore, the starter 13 can reliably accelerate the motor 15 with a desired voltage when the current value flowing through the three-phase coils L1 to L3 reaches a desired value.

Further, the starter 13 is provided with a voltage detector 42 for detecting the voltage levels of the voltages Vu, Vv, and Vw. Then, when the voltage detected by the voltage detector 42 becomes, for example, the voltage V1, the control circuit 48 turns on the switches 60 to 62 and 80 to 82, and further reduces the magnetic field of the coils 75 to 77. 46A is controlled. For this reason, the starter 11 can reliably accelerate the motor 15 at the desired voltage when the voltage levels of the voltages Vu, Vv, and Vw reach desired values.

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.

The control circuit 41 is a sequencer, but may be configured by, for example, a microcomputer and a memory. In this case, the microcomputer executes the program stored in the memory and executes the flowchart shown in FIG. As a result, even when the control circuit 41 is realized by a microcomputer or the like, the same effect as the starter 10 can be obtained.

10-13 Starter 15 Induction conductor (motor)
20 to 22 Step-down circuit 25 to 27 Step-down circuit 30 to 32 Switch 60 to 62 Switch 80 to 82 Switch 90 to 92 Switch 100 to 102 Switch 40 Timer 41, 45, 47, 48 Control circuit 42 Voltage detector 43 Current detector 44 Rotational speed detector 46A, 46B Magnetic circuit 70 to 72 Coil 75 to 772 Coil 95 to 97 Coil 110 to 112 Coil

Claims (13)

1. A first coil having a tap connected to a three-phase coil of the induction motor; a first switch connected between a power source for driving the induction motor and the first coil; and the first coil A second switch connected to a side to which the first switch is not connected, and a voltage that causes the tap to generate a voltage obtained by stepping down the power supply voltage of the power supply by controlling the first and second switches. Circuit,
   A third switch connected between the power source and the three-phase coil;
   A first control circuit that controls the first to third switches so as to turn on the first and second switches after turning on the first switch and then apply the power supply voltage to the three-phase coil;
   With
   The tap is
   The tap voltage when the first switch and the second switch are turned on is provided to be higher than the tap voltage when the first switch is turned on,
   An induction motor control device characterized by the above.
2. The induction motor control device according to claim 1,
   The first control circuit includes:
   Turning off the third switch after turning off at least the second switch of the first and second switches that are both turned on so that the power supply voltage is applied to the three-phase coil;
   An induction motor control device characterized by the above.
3. The induction motor control device according to claim 1 or 2, wherein
   A second coil connected between the first switch and the first coil;
   A magnetic circuit for reducing the magnetic field of the second coil;
   A second control circuit for controlling the magnetic circuit so that the magnetic field of the second coil decreases when the first and second switches are turned on;
   Further comprising,
   An induction motor control device characterized by the above.
4. The induction motor control device according to claim 3,
   The magnetic circuit is:
   A fourth switch;
   A third coil connected in parallel to the second coil to reduce the magnetic field of the second coil when the fourth switch connected in series is turned on;
   Including
   The second control circuit includes:
   Turning on the fourth switch when the first and second switches are turned on;
   An induction motor control device characterized by the above.
5. The induction motor control device according to claim 3,
   The magnetic circuit is:
   A fourth switch;
   A third coil that is magnetically coupled to the second coil and reduces the magnetic field of the second coil when the fourth switch is turned on;
   Including
   The second control circuit includes:
   Turning on the fourth switch when the first and second switches are turned on;
   An induction motor control device characterized by the above.
6. The induction motor control device according to claim 1 or 2, wherein
   A timer for measuring the time from when the first switch is turned on;
   The first control circuit includes:
   When the timer times a predetermined time, turning on both the first and second switches;
   An induction motor control device characterized by the above.
7. The induction motor control device according to claim 1 or 2, wherein
   A rotation speed detector for detecting the rotation speed of the induction motor;
   The first control circuit includes:
   When the rotational speed detected by the rotational speed detector after the first switch is turned on reaches a predetermined rotational speed, both the first and second switches are turned on;
   An induction motor control device characterized by the above.
8. The induction motor control device according to claim 1 or 2, wherein
   A current detector for detecting a current value flowing through the three-phase coil;
   The first control circuit includes:
   When the current value detected by the current detector becomes a predetermined value after the first switch is turned on, both the first and second switches are turned on;
   An induction motor control device characterized by the above.
9. The induction motor control device according to claim 1 or 2, wherein
   A voltage detector for detecting a level of the power supply voltage;
   The first control circuit includes:
   When the voltage level detected by the voltage detector reaches a predetermined level after the first switch is turned on, both the first and second switches are turned on.
   An induction motor control device characterized by the above.
10. The induction motor control device according to claim 3,
    A timer for measuring the time from when the first switch is turned on;
    The first control circuit includes:
    When the timer counts a predetermined time, both the first and second switches are turned on,
    The second control circuit includes:
    Controlling the magnetic circuit so that the magnetic field of the second coil decreases when the timer times a predetermined time;
    An induction motor control device characterized by the above.
11. The induction motor control device according to claim 3,
    A rotation speed detector for detecting the rotation speed of the induction motor;
    The first control circuit includes:
    When the rotational speed detected by the rotational speed detector after the first switch is turned on reaches a predetermined rotational speed, both the first and second switches are turned on,
    The second control circuit includes:
    Controlling the magnetic circuit so that the magnetic field of the second coil decreases when the number of rotations detected by the rotation number detector after the first switch is turned on reaches a predetermined number of rotations;
    An induction motor control device characterized by the above.
12. The induction motor control device according to claim 3,
    A current detector for detecting a current value flowing through the three-phase coil;
    The first control circuit includes:
    When the current value detected by the current detector reaches a predetermined value after the first switch is turned on, both the first and second switches are turned on,
    The second control circuit includes:
    Controlling the magnetic circuit so that the magnetic field of the second coil decreases when the current value detected by the current detector reaches a predetermined value after the first switch is turned on;
    An induction motor control device characterized by the above.
13. The induction motor control device according to claim 3,
    A voltage detector for detecting a level of the power supply voltage;
    The first control circuit includes:
    When the voltage level detected by the voltage detector after the first switch is turned on reaches a predetermined level, both the first and second switches are turned on,
    The second control circuit includes:
    Controlling the magnetic circuit such that the magnetic field of the second coil decreases when the voltage level detected by the voltage detector reaches a predetermined level after the first switch is turned on;
    An induction motor control device characterized by the above.

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