JP2009033942A - Induction motor starting controller and starting control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction motor starting controller which can perform induction motor starting control efficiently and conveniently at a low cost while suppressing adverse effect on the lifetime as compared with prior art by reducing the starting current of the induction motor. <P>SOLUTION: The induction motor starting controller 100 is provided with a magnetic energy regeneration bidirectional current switch 110 connected in series between an AC power supply 20 and an induction motor 10 and regulating a load voltage Vload applied to the induction motor 10, and a section 120 for controlling the magnetic energy regeneration bidirectional current switch 110 when starting the induction motor 10 so that an increase in number of revolutions of the induction motor 10 follows up an increase in load voltage Vload, thus increasing the load voltage Vload from 0 to the rated voltage Va of the induction motor 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction motor start control device and an induction motor start control method, and in particular, is a technique suitable for reducing the start current of an induction motor.

  An induction motor is an electric motor that generates a rotational torque corresponding to a slip by generating an induced current in an electric conductor of a rotor by a rotating magnetic field generated by a stator.

  When this induction motor is energized with an AC power source and directly turned on, a rated voltage is applied to the stator coil, but since the rotor is not rotating, the starting current flowing through the stator coil of the induction motor is It is determined by the primary and secondary total leakage reactance, and its value is generally small, so that a current 5 to 8 times the rated current flows through the stator coil of the induction motor. The flow of such a large current adversely affects the life of the induction motor from the standpoint of insulation of the motor winding.

  Therefore, various methods such as inverter startup, reactor startup, and Y-Δ startup have been conventionally employed as startup methods for preventing a large current from flowing through the induction motor.

JP 2004-260991 A Japanese Patent Laid-Open No. 2005-57980

  However, according to the inverter start-up as a conventional induction motor start-up method, the apparatus becomes complicated and the manufacturing cost is high, so it is mainly used for induction motors that require several hundred kW or more and a large motor capacity and high control performance. In the case of an electric motor that operates at a constant speed with a relatively small capacity of several to several tens of kW, a reactor starting method and a Y-Δ starting method are adopted as main starting methods.

  On the other hand, even when Y-Δ is started, a large inrush current flows when switching from Y to Δ, which adversely affects the life of the induction motor. Even when the reactor is started, the power factor at the time of starting is very low, so the starting efficiency is poor. Have startup problems. In addition, the double starting method has a problem in terms of manufacturing cost when used for a small capacity induction motor.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce the starting current of the induction motor and efficiently start it while suppressing the adverse effect on the life compared to the conventional one. It is to perform the control of the induction motor that can be performed simply and at low cost.

  In order to solve the above problems, according to one aspect of the present invention, a magnetic energy regenerative bidirectional current switch is connected in series between an AC power source and an induction motor and adjusts a load voltage applied to a coil of the induction motor. When starting the induction motor, the magnetic energy regenerative bidirectional current switch is controlled to increase the load voltage from 0 to the rated voltage of the induction motor so that the increase in the rotation speed of the induction motor follows the increase in the load voltage. An induction motor activation control device is provided.

  According to such a configuration, the magnetic energy regeneration bidirectional current switch can be controlled by the switch control unit. Then, by the controlled magnetic energy regenerative bidirectional current switch, a load voltage that increases from 0 to the rated voltage of the induction motor is applied to the induction motor so that the increase in the number of revolutions of the induction motor follows when the induction motor starts. Can be applied. In other words, the amplitude of the AC load voltage applied to the induction motor at the time of start-up is controlled from 0 so that the increase in the rotation speed of the induction motor follows the controlled magnetic energy regenerative bidirectional current switch. The voltage can be increased. Therefore, it is possible to prevent a large load voltage from being applied to the induction motor before the rotation speed of the induction motor increases.

  In addition, the magnetic energy regenerative bidirectional current switch is arranged in series on the first path with the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch opposite to each other in the conduction direction when the switch is off. A bridge circuit in which a second reverse conduction type semiconductor switch and a third reverse conduction type semiconductor switch are arranged in series on the second path so that conduction directions at the time of switch-off are opposite to each other; and a first reverse conduction type semiconductor switch And a capacitor connected between a first path between the second reverse conduction type semiconductor switch and a second path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch, The switch control unit includes a first reverse conducting semiconductor switch, a third reverse conducting semiconductor switch, a second reverse conducting semiconductor switch, and a fourth reverse at a switch switching timing every half cycle of the AC power supply voltage. By alternately turning on and off the semiconductor switch, the capacitor is charged and discharged, and by changing the switch switching timing, the charge amount and discharge amount of the capacitor are changed, and the load voltage is induced from 0 It may be increased up to the rated voltage of the motor.

  According to this configuration, the first reverse conducting semiconductor switch, the third reverse conducting semiconductor switch, the second reverse conducting semiconductor switch, the second reverse conducting semiconductor switch, and the second reverse conducting semiconductor switch at the switch switching timing for each half cycle of the AC power supply voltage. 4 Reverse conducting semiconductor switches are alternately turned on / off. By such switching, the capacitor of the magnetic energy regenerative bidirectional current switch is charged and discharged. If this discharge is not sufficient, the capacitor acts as a resistance to the circuit. Therefore, the magnetic energy regenerative bidirectional current switch can apply a low voltage lower than the supplied rated voltage to the induction motor immediately after startup.

In addition, a command voltage generator that generates a command voltage that increases from 0 to the rated voltage of the induction motor at a speed capable of following the increase in the rotation speed of the induction motor when the induction motor is started up, and applied to the induction motor The load voltage detection unit that detects the load voltage and the gate phase angle that represents the time difference between the switch switching timing of the magnetic energy regenerative bidirectional current switch and the zero cross point of the AC power supply voltage are changed so that the load voltage follows the command voltage. And a gate phase angle changing unit that controls the magnetic energy regeneration bidirectional current switch at a switch switching timing based on the gate phase angle changed by the gate phase angle changing unit.
According to such a configuration, the command voltage generating unit generates the command voltage that increases from 0 to the rated voltage at a speed that allows the increase in the rotation speed of the induction motor to follow. On the other hand, the load voltage applied to the induction motor is detected by the load voltage detector. Then, the gate phase angle change unit changes the gate phase angle so that the load voltage follows the command voltage, and at the switch switching timing shifted from the zero cross point of the AC power supply voltage by this gate phase angle, the switch control unit Control the magnetic energy regenerative bidirectional current switch. Therefore, the magnetic energy regeneration bidirectional current switch can apply a load voltage that changes following the command voltage to the induction motor. At this time, the command voltage increases at such a speed that the increase in the rotation speed of the induction motor can be followed, so that it is possible to prevent a large voltage from being applied before the rotation speed of the induction motor increases.

The gate phase angle changing unit may change the gate phase angle to an angle of 90 ° or more and 270 ° or less when the induction motor is started.
According to such a configuration, the magnetic energy regenerative bidirectional current switch is controlled by the switch control unit based on the gate phase angle of 90 ° or more and 270 ° or less changed by the gate phase angle changing unit, so that it is applied to the induction motor. The load voltage can be made lower than the rated voltage of the AC power supply.

The gate phase angle changing unit may decrease the gate phase angle from 180 ° to 130 ° so that the load voltage follows the command voltage when the induction motor is started.
According to this configuration, the gate phase angle can be reduced from 180 ° to 130 ° by the gate phase angle changing unit. Accordingly, the load voltage output from the magnetic energy regenerative bidirectional current switch can be increased to the rated voltage of the induction motor.

In order to solve the above-mentioned problem, according to another aspect of the present invention, an induction motor start that controls the start of the induction motor using a magnetic energy regenerative bidirectional current switch that adjusts a load voltage applied to the induction motor is provided. A control method,
When starting the induction motor, the magnetic energy regenerative bidirectional current switch is controlled, and the load voltage applied to the induction motor is rated from 0 so that the increase in the rotation speed of the induction motor follows the increase in the load voltage. An induction motor activation control method is provided, characterized by increasing to a voltage.
According to this configuration, it is possible to prevent a large load voltage from being applied to the induction motor before the rotation speed of the induction motor increases.

  In addition, the magnetic energy regenerative bidirectional current switch is arranged in series on the first path with the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch opposite to each other in the conduction direction when the switch is off. A bridge circuit in which a second reverse conduction type semiconductor switch and a third reverse conduction type semiconductor switch are arranged in series on the second path so that conduction directions at the time of switch-off are opposite to each other; and a first reverse conduction type semiconductor switch And a capacitor connected between a first path between the second reverse conduction type semiconductor switch and a second path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch, Including a first reverse conducting semiconductor switch, a third reverse conducting semiconductor switch, a second reverse conducting semiconductor switch, and a fourth reverse conducting semiconductor switch at a switch switching timing every half cycle of the AC power supply voltage. Are alternately turned on / off, the capacitor is charged and discharged, and the switch switching timing is changed to change the charge amount and discharge amount of the capacitor, thereby changing the load voltage from 0 to the rating of the induction motor. The voltage may be increased.

  In addition, it generates a command voltage that increases from 0 to the rated voltage of the induction motor at a speed that allows the increase in the rotation speed of the induction motor to follow the magnetic force so that the load voltage applied to the induction motor follows the command voltage. Change the gate phase angle that represents the time difference between the switch timing of the energy regenerative bidirectional current switch and the zero cross point of the AC power supply voltage, and control the magnetic energy regenerative bidirectional current switch at the switch switching timing based on the changed gate phase angle. May be.

  Further, the gate phase angle may be changed to an angle of 90 ° or more and 270 ° or less when the induction motor is started.

  Further, the gate phase angle may be decreased from 180 ° to 130 ° so that the load voltage follows the command voltage when the induction motor is started.

  As described above, according to the present invention, it is possible to reduce the starting current of the induction motor, and to control the induction motor that can be efficiently started up while suppressing the adverse effect on the life compared with the conventional one, at a simple and low cost. Can be done.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<Conventional motor>
Before describing the induction motor activation control device according to the embodiment of the present application, a conventional induction motor activation method, in particular, direct-injection activation will be described with reference to FIG. FIG. 6 is a graph showing the starting current flowing in the motor during the conventional direct-input starting.

  In FIG. 6, a vertical induction motor having a rated voltage of 400 V and an output power of 5.5 kW is used as an induction motor (hereinafter also referred to as “motor”). Shows time change.

  As shown in FIG. 6, it can be seen that a starting current of 83.4 A flows through the motor by applying a voltage of 400 V to the motor immediately after starting. This starting current is one factor that shortens the life of the motor from the viewpoint of insulation resistance of the motor winding, and is not preferable from the viewpoint of energy efficiency.

  Note that the large current flows when the motor is started as described above, because the rated voltage is applied before the rotor of the motor starts rotating. In other words, when the rotational speed of the rotor of the motor is lower than the rotational speed during normal operation, the starting current flowing in the stator coil of the motor is determined by the primary and secondary total leakage reactance, and the value is generally Therefore, a current 5 to 8 times the rated current flows through the stator of the induction motor.

  Therefore, the inventors of the present invention have considered the problems at the time of starting up the induction motor, and intensively studied the control of the motor, and as a result, have arrived at the present invention. Hereinafter, a motor control device according to an embodiment of the present invention will be described.

<Configuration of Motor Control Device 100 according to One Embodiment of the Present Invention>
First, with reference to FIG.1 and FIG.2, the structure of the motor control apparatus which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is an explanatory diagram for explaining an outline of a configuration of a motor control device according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining an example of a circuit configuration of the motor control device according to the present embodiment. It is explanatory drawing of.

  As shown in FIG. 1, the motor control device 100 according to the present embodiment is an example of an induction motor activation control device, and is arranged between an AC power supply 20 and a motor 10. The motor control device 100 is applied with an AC power supply voltage from the AC power supply 20 and applies an AC load voltage to the motor 10. The rated voltage (amplitude value) of the AC power supply voltage from the AC power supply 20 is Va, and the amplitude value of the AC load voltage applied to the motor 10 is Vload. Hereinafter, for convenience of explanation, the AC load voltage and the amplitude value of the load voltage are collectively referred to as “load voltage Vload”. When the magnitude of the voltage is described, the “load voltage Vload” The load voltage amplitude value is assumed to be indicated.

  In other words, the motor control device 100 applies the load voltage Vload to the motor 10 by transforming the rated voltage Va from the AC power supply. The motor control device 100 also adjusts the load voltage Vload applied to the motor 10 when the motor 10 is started. The motor 10 is activated when a switch 30 disposed between the AC power supply 20 and the motor control device 100 is turned on.

  As shown in FIG. 1, the motor control device 100 includes a MERS 110, a switch control unit 120, a phase detection unit 130, a gate phase angle change unit 140, a command voltage generation unit 150, and a load voltage detection unit 160. Have.

  The load voltage detection unit 160 detects a load voltage Vload that is a voltage applied to the motor 10, and outputs the detected load voltage Vload to the gate phase angle change unit 140. Note that the voltage detected by the load voltage detector 160 may be an effective value of Vload.

  For example, FIG. 2 shows a circuit configuration example of the load voltage detection unit 160 when the AC power supply 20 is a three-phase power supply and the motor 10 is a three-phase induction motor. As illustrated in FIG. 2, the load voltage detection unit 160 includes, for example, a three-phase to two-phase conversion circuit 161, an effective value circuit 162, and a low-pass filter 163.

  The three-phase to two-phase conversion circuit 161 converts Vload, which is an input three-phase AC voltage, into two phases. The effective value circuit 162 calculates the effective voltage of the interphase voltage of Vload converted into two phases. Further, the low pass filter 163 outputs Vrms from which low frequency noise of the effective voltage is removed to the gate phase angle changing unit 140.

  The command voltage generation unit 150 is configured by, for example, a lamp generator, and taps a voltage or the like from a path between the switch 30 and the MERS 110 to detect that the motor 10 is started, that is, the rated voltage Va is applied. To start operation. Then, the command voltage generation unit 150 that has started the operation generates a command voltage Vo that ramps up to the rated voltage of the motor 10 over a predetermined time when the motor 10 is started up, and sends it to the gate phase angle changing unit 140. Output. This command voltage Vo is a voltage used to adjust the increase amount of the load voltage Vload of the motor 10 at the time of startup.

  Based on the load voltage Vload detected by the load voltage detection unit 160 and the command voltage Vo generated by the command voltage generation unit 150, the gate phase angle changing unit 140 is a gate phase used as a temporal reference in the control of the MERS 110. Change the angle α. Then, the gate phase angle changing unit 140 outputs the changed gate phase angle α to the switch control unit 120. The gate phase angle α represents a temporal reference for when the switching of the MERS 110 is performed with respect to the cycle of the power supply voltage Va.

  A circuit configuration example of the gate phase angle changing unit 140 will be described with reference to FIG. As illustrated in FIG. 2, the gate phase angle changing unit 140 includes, for example, a difference circuit 141, a gain circuit 142, a limiter 143, and a gate phase angle determination circuit 144.

  The difference circuit 141 calculates a difference voltage ΔV between the load voltage Vload (for example, Vrms) detected by the load voltage detector 160 and the command voltage Vo generated by the command voltage generator 150. The gain circuit 142 amplifies the difference voltage ΔV calculated by the difference circuit 141 by K times, and outputs a change amount Δα of the gate phase angle α. That is, the gain circuit 142 calculates Δα = K × ΔV.

  The limiter 143 does not output when the change amount Δα of the gate phase angle α output from the gain circuit 142 is less than the lower limit value, and outputs the upper limit value when the change amount Δα exceeds the upper limit value. When it is less than the upper limit value, the change amount Δα is output. This lower limit value is an offset value in the circuit configuration, and the upper limit value is the maximum value of the change amount Δα of the gate phase angle α. The lower limit value and the upper limit value are set in advance based on the circuit configuration, actual measurement values, and the like.

  The gate phase angle determination circuit 144 determines the gate phase angle α by changing the gate phase angle α by the change amount Δα output from the limiter 143 or its upper limit value from the already set value. Then, the gate phase angle determination circuit 144 outputs the newly determined gate phase angle α to the switch control unit.

  The phase detection unit 130 taps the voltage between the AC power supply 20 and the MERS 110 and between the MERS 110 and the motor 10 to detect the phase of the power supply voltage having the rated voltage Va and the phase of the load voltage Vload. . Then, the phase detection unit 130 supplies information regarding these phases to the switch control unit 120.

  The switch control unit 120 controls the MERS 110 based on the phase of the power supply voltage and the load voltage Vload detected by the phase detection unit 130 and the gate phase angle α output by the gate phase angle changing unit 140. The control by the switch control unit 120 will be described later.

  A circuit configuration example of the switch control unit 120 will be described with reference to FIG. As illustrated in FIG. 2, the switch control unit 120 includes a switch switching timing determination circuit 121 and a gate signal generation circuit 122.

  The switch switching timing determination circuit 121 sets the gate phase angle changed by the gate phase angle changing unit 140 from the zero cross point of the phase of the power supply voltage detected by the phase detecting unit 130, as the switch switching timing for switching ON / OFF of the switch of the MERS 110. Determine by shifting by α. Then, the switch switching timing determination circuit 121 outputs the determined switch switching timing to the gate signal generation circuit 122.

  The gate signal generation circuit 122 generates a gate signal for turning on / off the switch of the MERS 110 and outputs the gate signal to each switch of the MERS 110. At this time, the gate signal generation circuit 122 switches the switch of the MERS 110 between ON and OFF at the switch switching timing determined by the switch switching timing determination circuit 121.

  The MERS 110 is an example of a magnetic energy recovery bidirectional current switch (MERS) disclosed in Patent Document 1, and is disposed between the AC power supply 20 and the motor 10. The MERS 110 is a circuit that is controlled by the switch control unit 120, transforms a power supply voltage having the rated voltage Va supplied from the AC power supply 20, and applies the load voltage Vload to the motor 10. Can be adjusted. Incidentally, the control of the induction motor by such a magnetic energy regenerative bidirectional current switch is also disclosed in Patent Document 2.

(Configuration of MERS110)
The configuration of the MERS 110 will be described with reference to FIG.
As shown in FIG. 1, the MERS 110 includes a bridge circuit and a capacitor C.

  The bridge circuit is configured by four reverse conducting semiconductor switches 111 to 114 arranged in two paths, and the capacitor C is disposed between the two paths of the bridge circuit.

  More specifically, the bridge circuit includes an AC terminal d (hereinafter referred to as a terminal d) connected to the motor 10 via a terminal b from an AC terminal a (hereinafter referred to as a terminal a) connected to the AC power supply 20. And a second path that is a path from the terminal a to the terminal d via the terminal c, and the first path has a reverse conduction type between the terminal d and the terminal b. The semiconductor switch 111 is disposed, and the reverse conducting semiconductor switch 114 is disposed between the terminal b and the terminal a. In the second path, the reverse conducting semiconductor switch 112 is disposed between the terminal d and the terminal c, and the reverse conducting semiconductor switch 113 is disposed between the terminal c and the terminal a. And the capacitor | condenser C is arrange | positioned between the terminal b and the terminal c.

  Each of the reverse conducting semiconductor switches 111 to 114 is a switch that conducts in one direction (hereinafter referred to as “forward direction”) when the switch is OFF, and conducts in another direction (hereinafter referred to as “reverse direction”) when the switch is ON. For example, it is configured by parallel connection of a semiconductor switch and a diode. More specifically, each of the reverse conducting semiconductor switches 111 to 114 includes one diode D1 to D4 and one semiconductor switch S1 to S4 connected in parallel to the diode D1 to D4.

  However, the reverse conduction type semiconductor switch is not limited to such an example, and may be any switch as long as the above conduction control is possible. For example, it may be a power MOS FET, a reverse conduction type GTO thyristor, or the like. A parallel connection of a semiconductor switch such as an IGBT and a diode may be used.

  The reverse conducting semiconductor switches 111 to 114 are arranged so that the forward direction is as follows. That is, assuming that the reverse conducting semiconductor switch 111 and the reverse conducting semiconductor switch 113 are a first pair and the reverse conducting semiconductor switch 112 and the reverse conducting semiconductor switch 114 are a second pair, the first pair of reverse conducting semiconductor switches. 111 and reverse conduction type semiconductor switch 113 are arranged so that the forward direction is the same direction, and the second pair of reverse conduction type semiconductor switch 112 and reverse conduction type semiconductor switch 114 are such that the forward direction is the same direction. The first pair and the second pair are arranged such that the forward directions are opposite to each other.

  In other words, reverse conduction type semiconductor switches arranged in parallel are arranged so that each forward direction is reverse, and reverse conduction type semiconductor switches arranged in series are arranged so that each forward direction is reverse. Is done. In other words, the reverse conducting semiconductor switches arranged on the diagonal line are arranged so that the forward directions are the same.

  The switches ON / OFF of the reverse conducting semiconductor switches 111 to 114, that is, the semiconductor switches S1 to S4 are turned ON / OFF by inputting ON signals to the respective gates G1 to G4. More specifically, each of the gates G1 to G4 is connected to the switch control unit 120, and a gate signal (ON signal) generated by the switch control unit 120 is input. That is, when the gate signal of the switch control unit 120 is input, each reverse conducting semiconductor switch 111 to 114 conducts not only in the forward direction but also in the reverse direction.

(Characteristics of MERS110)
Here, the characteristic of MERS110 is demonstrated by demonstrating the operation | movement of MERS110.

  In the MERS 110, the reverse conducting semiconductor switches in the pair are turned ON / OFF at the same time, and when one pair is ON, the other pair is turned OFF. Here, switching from the state where one pair is turned on and the other pair is turned off to the state where one pair is turned off and the other pair is turned on is called “switching”, and this switching is performed. The time point is referred to as “switch switching timing”.

  This switching is performed in a cycle that is half the cycle of the power supply voltage of the AC power supply 20. A time point when the power supply voltage becomes 0 is referred to as a “zero cross point”, and the time difference between the zero cross point and the switch switching timing is the above-described “gate phase angle α”. In other words, switching is performed at a period in which the phase is shifted from the zero cross point by the gate phase angle α.

  Furthermore, the gate phase angle α is determined to be 0 ° when all reverse conducting semiconductor switches are conducted in the direction in which the power supply voltage is applied. That is, at α = 0 °, when Va is applied in the direction shown in FIG. 1, the reverse conducting semiconductor switches 111 and 113 are turned on, and the terminal a → terminal b → terminal d and the terminal a → terminal as the conduction paths. c → terminal d is secured. When Va is applied in the direction opposite to that shown in FIG. 1, the reverse conducting semiconductor switches 112 and 114 are turned on, and the terminal d → terminal c → terminal a and the terminal d → terminal b → terminal are connected as conduction paths. a is secured.

  When the gate phase angle α is shifted from 0 °, a time during which one of the pair of reverse conducting semiconductor switches does not conduct in the direction in which the power supply voltage is applied occurs. In other words, when α ≠ 0 °, for example, when Va is applied in the direction shown in FIG. 1, only the reverse conducting semiconductor switches 112 and 114 are turned on for the time interval corresponding to the size of α, and the capacitor A state in which a voltage is applied to C (a state in which the conduction path is changed from terminal a → terminal b → terminal c → terminal d) occurs. Similarly, when the voltage is applied in the reverse direction, only the reverse conducting semiconductor switches 111 and 113 are turned on and the voltage is applied to the capacitor C during the time interval corresponding to the magnitude of α (the conduction path is Terminal d → terminal b → terminal c → terminal a). The voltage applied to the capacitor C is applied in one direction regardless of the direction of the power supply voltage (in FIG. 1, terminal b → terminal c).

  Therefore, if the gate phase angle α is shifted from 0 °, the period during which the capacitor C is charged with respect to the cycle of the power supply voltage, and all the reverse conducting semiconductor switches are conducted in the direction in which the power supply voltage is applied. There occurs a period during which the capacitor C is discharged. As a result, by controlling the gate phase angle α, the charging and discharging of the capacitor C can be adjusted, and the voltage (load voltage Vload in FIG. 2) output from the MERS 110 can be controlled. . Here, the magnitude of the output voltage is expressed by Vload = Va × sin α / cos Φ. Note that Φ is a power factor angle of the motor 10.

  The change of the output voltage Vload with respect to the gate phase angle α will be described in detail as follows.

  When Va is applied as the power supply voltage, the capacitor C is charged and discharged by switching of the MERS 110, and when discharging, the capacitor C outputs the voltage of the vector Vmers. However, the vector Vmers is delayed or preceded by the gate phase angle α with respect to the vector Va. Therefore, the sum voltage of the vector Va and the vector Vmers is output from the MERS 110 as Vload. A current I having a leading phase or a lagging phase Φ flows through a load to which Vload is applied due to a reactance component or the like.

  Further, since the vector Vload is the sum of the vector Va and the vector Vmers, depending on | Vmers |, | Vload |> | Va | is satisfied when 0 ° <α <90 °. Therefore, the MERS 110 can output a voltage higher than Va according to the gate phase angle α. On the other hand, when α> 90 °, | Vload | <| Va |. The value of the gate phase angle α at which | Vload | = | Va |, which is the boundary between the two, varies depending on the change of | Vmers |, but does not become 90 ° or less. | Vmers | varies depending on the capacitance of the capacitor C, the characteristics of the load, the magnitude of the gate phase angle α, and the like.

  FIG. 3 shows a measurement example of the output voltage | Vload | that changes with respect to the gate phase angle α. FIG. 3 is a graph showing an example of a change in the output voltage of the MERS 110 with respect to the gate phase angle.

  As shown in FIG. 3, when α = 0 °, a voltage substantially equal to the input voltage Va is output. However, when α is increased, Vload larger than Va is output, and when α = 130 °, | Vload | = | Va |. When α is further increased, | Vload | becomes smaller than | Va |, and | Vload | = 0 when α = 180 °. Note that when α> 180 °, Vload shows a change that is reversed when α = 180 °.

  Therefore, in this measurement example, by setting 130 ° <α <230 °, | Vload | can be made less than | Va |. Further, the gate phase angle α at which | Vload | = | Va | varies depending on characteristics such as the capacitance of the capacitor C, the reactance component of the load, and the like, and by appropriately selecting these, 90 ° <α <230 ° | Vload | can be less than | Va |.

<Operation of Motor Control Device 100 According to One Embodiment of the Present Invention>
The configuration of the motor control device 100 according to an embodiment of the present invention has been described above.
Next, the operation of the motor control device 100 having the above configuration will be described with reference to FIG. FIG. 4 is a flowchart for explaining one operation of the motor control device 100 according to the present embodiment.

(Command voltage generation step S101)
First, when a switch 30 that is an example of a switch that controls ON / OFF of the motor 10 is turned on, the AC power source 20, the MERS 110 of the motor control device 100, and the motor 10 form one closed circuit. When this closed circuit is formed, the command voltage generator 150 starts operating. The command voltage generation unit 150 that has started the operation outputs the command voltage Vo to the gate phase angle changing unit 140.

  The command voltage Vo is a voltage that increases in a ramp shape from 0 V to the rated voltage Va over a predetermined time from the start of the start of the motor 10. That is, the command voltage Vo increases in a linear function from 0 V to the rated voltage Va. The increase in the command voltage Vo is set in advance with reference to actually measured values. The increase amount per unit time of the command voltage Vo is set to an amount that can follow the increase in the rotation speed of the rotor of the motor 10.

  In other words, when the increase amount of the command voltage Vo is increased, the load voltage Vload also increases following the increase of the command voltage Vo by the operation of the motor control device 100 described later. That is, when the rotational speed of the rotor of the motor 10 is low, that is, when the increase in the rotational speed of the rotor of the motor 10 does not follow the increase in the load voltage Vload, the motor 10 is started greatly. Current I flows. Accordingly, the maximum value of the starting current I to the motor 10 is determined in advance, the actual starting current I flowing to the motor 10 is actually measured, and the increase amount of the load voltage Vload is within a range where the starting current I does not exceed the maximum value. Determine. The increase amount of the command voltage Vo can be determined from the increase amount of the load voltage Vload determined by the actual measurement.

(Load voltage detection step S103)
Next, the load voltage detection unit 160 detects the load voltage Vload of the motor 10.
More specifically, for example, the load voltage detection unit 160 taps a voltage from a path between the MERS 110 and the load voltage Vload. Then, the three-phase to two-phase conversion circuit 161 converts the three-phase voltage into a two-phase voltage, and the effective value circuit 162 calculates the effective voltage between the two phases from the converted two-phase voltage. Thereafter, the low-frequency noise is removed from the effective voltage by the low-pass filter 163. The load voltage Vload (effective voltage from which low frequency noise has been removed, for example, Vrms) is output to the gate phase angle changing unit 140.

(Comparison step S105 between the command voltage Vo and the load voltage Vload)
The gate phase angle changing unit 140 that receives the command voltage Vo and the load voltage Vload compares the command voltage Vo with the load voltage Vload. If the difference between the two is less than the offset value, the operation ends. If the difference between the two is equal to or greater than the offset value, the process proceeds to the next step.

  More specifically, for example, the difference circuit 141 calculates the difference voltage ΔV obtained by subtracting the load voltage Vload from the command voltage Vo. Then, the gain circuit 142 calculates the change amount Δα of the gate phase angle α by multiplying the difference voltage ΔV by K, and when the change amount Δα is equal to or less than the offset value, the limiter 143 outputs the change amount. End the operation without On the other hand, when the change amount Δα is equal to or greater than the offset value, the change amount Δα is output to the gate phase angle determination circuit 144. At this time, if the change amount Δα is equal to or greater than the offset value and exceeds the predetermined upper limit value, the upper limit value is output to the gate phase angle determination circuit 144 instead of the change amount Δα.

  This offset value is a value determined in advance from an actual measurement value, a circuit configuration, and the like, and can be changed as appropriate. Even if the gate phase angle α is set to an angle (for example, 130 °) such that | Vload | = | Va |, the load voltage Vload applied to the motor 10 is not limited to the circuit resistance or reactance component from the power supply voltage Va. Descent due to etc. The magnitude of the dropped voltage value can be measured and set as the offset value. Further, the offset value can be made zero by adjusting the control gain in consideration of the resistance and reactance component of each circuit.

  The upper limit value is also a value determined in advance from an actual measurement value, a circuit configuration, and the like, and can be changed as appropriate. If the change amount Δα of the gate phase angle α is set to a large value, the change amount of the gate phase angle α is too large, and the difference between the command voltage Vo and the load voltage Vload increases. Therefore, this upper limit value is preferably determined in advance from an actual measurement value, a circuit configuration, or the like.

(Gate phase angle changing step S107)
The description returns to the operation of the motor control device 100.
The case where the change amount Δα of the gate phase angle α is output from the limiter 143 in the comparison step S105 will be described below. The same applies to the case where the upper limit value is output instead of the change amount Δα. Therefore, the case where the change amount Δα is output will be described below.

  That is, as the next operation, the gate phase angle changing unit 140 changes the gate phase angle α by the change amount Δα and sets it as a new gate phase angle α and outputs it to the switch control unit 120.

  More specifically, the gate phase angle determination circuit 144 that has received the change amount Δα sets the new gate phase angle α to a value obtained by changing the change amount Δα from the previously set gate phase angle α. . Then, the gate phase angle determination circuit 144 outputs the newly set gate phase angle α to the switch control unit 120.

(Switch control step S109)
Then, a gate for turning on / off each of the reverse conducting semiconductor switches 111 to 114 of the MERS 110 at the switch switching timing based on the gate phase angle α by the switch control unit 120 that has received the newly set gate phase angle α. A signal is generated and sent to MERS 110. As a result, the MERS 110 is controlled by this gate signal.

  The MERS 110 that has received the input of the gate signal applies the load voltage Vload changed based on the gate phase angle α to the motor 10 as described above due to the change in the gate phase angle α.

  The series of operations of the motor control device 100 has been described above. In this operation, the operation after the load voltage detection step (S103) is sequentially executed while the switch control step (S109) is performed. Therefore, after the motor 10 is started, in the load voltage detection step (S103) to the switch control step (S109), the difference voltage ΔV (the change amount Δα in this embodiment) between the command voltage Vo and the load voltage Vload is an offset value. Repeat until less than. On the other hand, independently of this operation, the command voltage Vo generated in the command voltage generation step (S101) changes from 0 V to the rated voltage Va over a predetermined time. Accordingly, the load voltage Vload output from the MERS 110 changes following the change in the command voltage Vo through the load voltage detection step (S103) to the switch control step (S109).

  As a result, the load voltage Vload increases to the vicinity of the rated voltage Va which is the maximum value of the command voltage Vo, and after a predetermined time, the rated voltage Va similar to that during normal operation is applied to the motor 10 (Vload≈Va ). Then, the motor control device 100 that has finished the operation at the time of starting the motor 10 performs the normal operation of the motor 10 by performing switching at the gate phase angle α determined last.

<Example of Operation of Motor Control Device 100 according to One Embodiment of the Present Invention>
An example of this operation will be described with reference to FIG.
FIG. 5 is a graph for explaining an example of the operation of the motor control device 100 according to the present embodiment.

  5A is a graph showing the time change of the voltage such as the load voltage Vload and the starting current I flowing through the motor 10, and FIG. 5B is a graph showing the time change of the gate phase angle α. . In the following description, for example, the rated voltage Va of the AC power supply 20 is about 400 V, and the rated current I is about 9.4 A. At this time, for example, the offset value is about 25 V in terms of voltage.

  As shown in FIG. 5A, when the time is 0 second, the switch 30 is turned on and the motor 10 is started. The command voltage generation unit 150 outputs a command voltage Vo that increases over a period of about 25 seconds from 0 V to the rated voltage Va, for example.

  By outputting the command voltage Vo, the gate phase angle α is changed as shown in FIG. 5B through the above operation. The change amount Δα of the gate phase angle α is determined by multiplying the difference voltage ΔV between the command voltage Vo and the load voltage Vload by K as described above.

A qualitative description of how the gate phase angle α is changed is as follows.
As shown in (A), for example, there is a difference of a difference voltage ΔV1 between the command voltage Vo and the load voltage Vload at 15 seconds after the switch 30 is turned on. This ΔV1 is multiplied by K, and a change amount Δα1 shown in (B) is calculated. When Δα1 is not less than the offset value and not more than the upper limit value, the gate phase angle α1 set at the time of 15 seconds is changed by Δα1, and a new gate phase angle α2 is set. Then, at the next time point (for example, Δt seconds from the time point of 15 seconds), the switch switching timing is determined by the gate phase angle α2, and the MERS 110 is controlled at this switch switching timing. As a result, the load voltage Vload that was V1 at the time of 15 seconds is increased to V2 at the next time (for example, Δt seconds after the time of 15 seconds). Therefore, by repeating this operation, the load voltage Vload increases following the increase in the command voltage Vo.

  As shown in FIG. 5B, the gate phase angle α changed as described above is changed from about 165 ° immediately after startup (0 seconds) to 130 ° at about 13 seconds and about 25 seconds. And has been reduced. Although it is possible to set the gate phase angle α immediately after activation to 180 °, it is 165 ° in this example. This is because the voltage applied when the motor 10 was started last time remains as a residual voltage in the winding of the stator of the motor 10, and as shown in FIG. This comes from taking a predetermined value that is not zero. Therefore, by removing this residual voltage, the gate phase angle α at the time of 0 second can be set to 180 °. Needless to say, by removing this residual voltage, the load voltage Vload at 0 second can be reduced to zero.

  The starting current I flowing through the motor 10 at this time is shown in FIG. The starting current I gradually increases after starting the motor 10 (from the time of 0 second), drops after reaching a maximum of 35.9 A, and after about 22 seconds, is almost equal to the rated current value of the motor 10. It is equal to about 9.37A.

  As described above, in the case of the conventional direct-injection start-up, the motor 10 according to the present embodiment has a motor 10 at the time of start-up as compared with the motor 10 having a start-up current of about 83.4 A at the maximum. It can be seen that the maximum value of the start-up current I flowing through can be reduced to about ½ times. It is possible to further reduce the maximum value of the starting current I flowing through the motor 10 by changing the increase amount of the command voltage Vo, the circuit configuration, and the like.

<Effects of the motor control device 100 according to the present embodiment>
The configuration and operation of the motor control device 100 according to one embodiment of the present invention have been described above. According to the motor control device 100, since the soft start can be performed by reducing the starting current I flowing in the motor 10 when the motor 10 is started, the load applied to the winding of the motor 10 can be reduced. Longer life of the motor 10 can be realized.

  Since the configuration of the motor control device 100 is simple as described above and each component circuit is also inexpensive, the manufacturing cost is lower than that required for other startup methods such as reactor startup and Y-Δ startup. It is possible to reduce.

  Further, the capacitor C of the MERS 110 can regenerate part of the difference in electric energy between the rated voltage Va supplied from the AC power supply 20 and the load voltage Vload output from the MERS 110. Therefore, it is possible to increase the power factor when the motor 10 is started.

  Moreover, since the motor control apparatus 100 can reduce the starting current I of the motor 10 and improve the power factor, it can reduce the power consumption at the time of starting the motor 10 and increase the energy efficiency. Can do.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above embodiment, the circuit configuration example of the switch control unit 120, the gate phase angle changing unit 140, and the load voltage detecting unit 160 has been described. However, the present invention is not limited to such an example, and the switch control unit 120, the gate phase angle changing unit 140, and the load voltage detecting unit 160 may be configured by any circuit that can perform the above-described operation.

  In the above embodiment, the gate phase angle changing unit 140 includes the gate phase angle determination circuit 144. However, the present invention is not limited to such an example, and the gate phase angle changing unit 140 may not include the gate phase angle determination circuit 144, for example. In this case, for example, the gate phase angle changing unit 140 outputs the change amount Δα or the upper limit value of the gate phase angle α to the switch control unit 120, and the switch control unit 120 switches the switch by the change amount Δα or the upper limit value. The timing may be changed.

  In the above embodiment, the command voltage Vo is a voltage that increases in a ramp shape from 0 V to the rated voltage Va, but the present invention is not limited to such an example. The command voltage Vo may be ramp-like, that is, increase in a linear function with respect to time, for example, may increase in a quadratic function with respect to time, or may increase in an inverse function. . In addition, the command voltage Vo can be set so as to increase gradually over a predetermined time.

  In the above-described embodiment, the limiter 143 is disposed at the subsequent stage of the gain circuit 142, and the offset value and the upper limit value are values corresponding to the change amount Δα of the gate phase angle α. However, the present invention is not limited to such an example. For example, the limiter 143 may be disposed in the previous stage of the gain circuit 142 and may set an offset value and an upper limit value as values for the difference voltage ΔV output from the difference circuit 141. Since the offset value and the upper limit value in this case are determined in the same manner as in the above embodiment, a detailed description thereof is omitted here.

It is explanatory drawing for demonstrating the outline | summary of a structure of the motor control apparatus which concerns on one Embodiment of this invention. It is explanatory drawing for demonstrating an example of the circuit structure of the motor control apparatus which concerns on the same embodiment. It is a graph which shows an example of the change of the output voltage of MERS with respect to a gate phase angle. 3 is a flowchart for explaining an operation of the motor control device according to the embodiment. It is a graph for demonstrating an example of operation | movement of the motor control apparatus which concerns on the same embodiment. It is a graph which shows the starting current which flows into a motor at the time of the conventional direct drive.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 20 AC power supply 30 Switch 100 Motor control apparatus 110 MERS
DESCRIPTION OF SYMBOLS 120 Switch control part 121 Switch switching timing determination circuit 122 Gate signal generation circuit 130 Phase detection part 140 Gate phase angle change part 141 Difference circuit 142 Gain circuit 143 Limiter 144 Gate phase angle determination circuit 150 Command voltage generation part 160 Load voltage detection part 161 Three-phase to two-phase conversion circuit 162 RMS circuit 163 Low-pass filter 111, 112, 113, 114 Reverse conduction type semiconductor switch D1, D2, D3, D4 Diode S1, S2, S3, S4 Semiconductor switch G1, G2, G3, G4 Gate C Capacitor L Reactance component R Resistance component

Claims (10)

A magnetic energy regenerative bidirectional current switch that is connected in series between the AC power source and the induction motor and adjusts a load voltage applied to the induction motor;
At the time of starting the induction motor, the magnetic energy regenerative bidirectional current switch is controlled so that the increase of the rotation speed of the induction motor follows the increase of the load voltage from 0 to the induction motor. A switch controller that increases to the rated voltage;
An induction motor activation control device comprising: The magnetic energy regenerative bidirectional current switch is
The first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch are arranged in series in the first path with the conduction directions at the time of switch off being opposite to each other, and the second reverse conduction type semiconductor switch is arranged in the second path. A bridge circuit in which the third reverse conducting semiconductor switch and the third reverse conducting semiconductor switch are arranged in series with the conducting directions at the time of switch-off being opposite to each other;
The first path between the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch, and the first path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch. A capacitor connected between the two paths;
Including
The switch control unit
The first reverse conduction type semiconductor switch, the third reverse conduction type semiconductor switch, the second reverse conduction type semiconductor switch, and the fourth reverse conduction type semiconductor switch at a switch switching timing for each half cycle of the AC power supply voltage. And alternately turning on and off to charge and discharge the capacitor, and
The induction according to claim 1, wherein the switch switching timing is changed to change a charge amount and a discharge amount of the capacitor to increase the load voltage from 0 to a rated voltage of the induction motor. Electric motor start control device. A command voltage generator that generates a command voltage that increases from 0 to the rated voltage of the induction motor at a speed that allows an increase in the number of rotations of the induction motor to follow when the induction motor is started;
A load voltage detector for detecting a load voltage applied to the induction motor;
A gate phase angle changing unit that changes a gate phase angle representing a time difference between the switch switching timing of the magnetic energy regenerative bidirectional current switch and a zero cross point of the AC power supply voltage so that the load voltage follows the command voltage. When,
Further comprising
The switch control unit controls the magnetic energy regeneration bidirectional current switch at the switch switching timing based on the gate phase angle changed by the gate phase angle changing unit. Induction motor start control device.   The induction motor activation control device according to claim 3, wherein the gate phase angle changing unit changes the gate phase angle to an angle of 90 ° or more and 270 ° or less when the induction motor is activated.   The gate phase angle changing unit reduces the gate phase angle from 180 ° to 130 ° so that the load voltage follows the command voltage when the induction motor is started. 4. The induction motor activation control device according to 4. An induction motor activation control method for controlling activation of the induction motor using a magnetic energy regenerative bidirectional current switch for adjusting a load voltage applied to the induction motor,
When starting up the induction motor, the magnetic energy regenerative bidirectional current switch is controlled to reduce the load voltage applied to the induction motor to 0 so that the increase in the rotation speed of the induction motor follows the increase in the load voltage. The induction motor starting control method is characterized in that the induction motor is increased to the rated voltage of the induction motor. The magnetic energy regenerative bidirectional current switch is
The first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch are arranged in series in the first path with the conduction directions at the time of switch off being opposite to each other, and the second reverse conduction type semiconductor switch is arranged in the second path. A bridge circuit in which the third reverse conducting semiconductor switch and the third reverse conducting semiconductor switch are arranged in series with the conducting directions at the time of switch-off being opposite to each other;
The first path between the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch, and the first path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch. A capacitor connected between the two paths;
Including
The first reverse conduction type semiconductor switch, the third reverse conduction type semiconductor switch, the second reverse conduction type semiconductor switch, and the fourth reverse conduction type semiconductor switch at a switch switching timing every half cycle of the AC power supply voltage, , Alternately on / off to charge and discharge the capacitor, and
The charge amount and discharge amount of the capacitor are changed by changing the switch switching timing to increase the load voltage from 0 to a rated voltage of the induction motor. Induction motor activation control method. Generating a command voltage that increases from 0 to the rated voltage of the induction motor at a speed at which an increase in the rotation speed of the induction motor can follow,
The gate phase angle representing the time difference between the switch switching timing of the magnetic energy regeneration bidirectional current switch and the zero cross point of the AC power supply voltage is changed so that the load voltage applied to the induction motor follows the command voltage. ,
The induction motor activation control method according to claim 7, wherein the magnetic energy regeneration bidirectional current switch is controlled at the switch switching timing based on the changed gate phase angle.   The induction motor activation control method according to claim 8, wherein the gate phase angle is changed to an angle of 90 ° or more and 270 ° or less when the induction motor is activated.   The induction motor start control according to claim 9, wherein the gate phase angle is reduced from 180 ° to 130 ° so that the load voltage follows the command voltage when the induction motor is started. Method.

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