JP2005318754A - Inverter device for motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the rise of a terminal voltage caused by the overcharging of a smoothing capacitor, when all switching elements that constitute a voltage-type inverter are controlled into off-states. <P>SOLUTION: This inverter device for motor drive comprises: a rectifier 2 that rectifies an AC voltage; the smoothing capacitor 3 that smoothes a DC voltage output by the rectifier 2; and the voltage-type inverter 4 that converts main circuit voltages appearing at both ends of the smoothing capacitor 3 into AC voltages applied to a motor 5 by the switching operation of the semiconductor switching element. The inverter device also comprises a control means that makes the semiconductor switching element constituting the voltage-type inverter 4 conduct the switching operation so that a current flows to the motor 5 when the main circuit voltages appearing at both the ends of the smoothing capacitor 3 become higher than a threshold voltage, when the semiconductor switching elements that constitute the voltage-type inverter 4 stop their swithcing operations. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inverter device for driving a motor.

  FIG. 8 is a diagram illustrating a configuration example of a conventional inverter device for driving a motor. As shown in FIG. 8, the conventional motor drive inverter device includes a rectifier 2 that rectifies the output AC voltage of the AC power supply 1, a smoothing capacitor 3 that smoothes the output DC voltage of the rectifier 2, and both ends of the smoothing capacitor 3. In the basic configuration of the voltage type inverter 4 that switches the appearing DC voltage and applies the AC voltage to the electric motor 5, as a configuration for controlling the voltage type inverter 4, a start command, a stop command, a rotation speed command, etc. An operation command setter 9 for setting an operation command, a gate signal generation circuit 20 for generating a gate signal for driving the electric motor 5 in accordance with the operation command set by the operation command setter 9, and a gate signal generation circuit 20 A gate drive circuit 1 for applying a voltage corresponding to the gate electrode of the switching element constituting the voltage type inverter 4 by the generated gate signal It is equipped with a door.

  In this type of motor drive inverter device, for example, as shown in FIG. 9, a regenerative converter is often connected in parallel. Hereinafter, a description will be given with reference to FIG. In FIG. 9, the regenerative converter 50 includes a transistor bridge 102 connected to an output terminal (point A) of the AC power supply 1 via a series circuit of a resistor 100 and an AC reactor 101 as disclosed in Patent Document 1, for example. The motor 105 connected to the inverter bridge 104 is driven by a configuration in which the AC side terminal is connected and the smoothing capacitor 103 and the inverter bridge 104 are connected between the DC side terminals of the transistor bridge 102.

  At this time, the AC reactor 40 for power factor improvement is arranged between the rectifier 2 and the point A that is the connection end of the AC power source 1 and the regenerative converter 50, and the line between the AC reactor 40 and the rectifier 2. A noise filter line capacitor 41 is connected between them. The noise filter line-to-line capacitor 41 is disclosed in, for example, Patent Document 2, but the DC choke coil shown in Patent Document 2 is omitted here.

  Here, the operation in the configuration shown in FIG. 9 to which the regenerative converter 50 is connected will be described. FIG. 10 is a diagram for explaining the regenerative current that flows from the regenerative converter 50 to the AC power supply side in FIG. 9. FIG. 11 is a diagram for explaining the state of the line voltage at the point A shown in FIG.

  In FIG. 9, when a regenerative operation occurs in the regenerative converter 50, a difference voltage between the maximum phase voltage and the minimum phase voltage among the three phase voltages of the AC power supply 1 is applied to the series circuit of the resistor 100 and the AC reactor 101. Accordingly, the regenerative current increases while being limited by the impedance, and a regenerative current as shown in FIG. 10 flows. At this time, since the regenerative current changes the phase flowing every 60 degrees of the power supply frequency, as shown in FIG. 10, the regenerative current shows a change that suddenly drops to zero voltage every 60 degrees.

  Therefore, as shown in FIG. 11, the output terminal of the AC power source 1 is in accordance with the ratio between the power source impedance of the AC power source 1 and the impedance of the series circuit of the resistor 100 and the AC reactor 101 that are constituent elements of the regenerative converter 50. A sudden drop occurs in the line voltage at the point A. In particular, the resistor 100 is often used with a very small resistance value in order to reduce loss, and the AC reactor 101 is often used with a small inductance value from the viewpoint of miniaturization. In addition, since resonance due to a capacitive component existing in the system or the like is also added, when the power supply capacity of the AC power supply 1 is relatively small, a sudden drop as shown in FIG. 11 may reach near zero voltage.

  When the conventional inverter device for driving a motor shown in FIG. 8 is connected to the output terminal A of the AC power supply 1 causing a sudden drop as described above via the AC reactor 40 and the line-to-line capacitor 41, the AC reactor 40 Due to resonance between the line capacitor 41 and the line capacitor 41, the voltage of the line capacitor 41 may be higher than the voltage of the AC power supply 1.

  A voltage higher than the voltage of the AC power supply 1 generated in the line capacitor 41 is rectified by the rectifier 2 and supplied to the smoothing capacitor 3. At this time, in the normal operation in which the switching element constituting the voltage type inverter 4 is switched and the voltage and current are supplied to the electric motor 5, the charging power to the smoothing capacitor 3 by the above high voltage is supplied. Is consumed by the loss generated in the switching element of the voltage type inverter 4, the loss such as the iron loss and the copper loss generated in the electric motor 5, and the shaft output of the electric motor 5, so that the smoothing capacitor 3 is overcharged. There is nothing.

Japanese Patent Laid-Open No. 5-304779 Japanese Utility Model Publication No. 1-61893

  However, when the motor command is stopped when the switching element of the voltage type inverter 4 is completely cut off by the stop command of the operation command setter 9 and no voltage or current is supplied to the motor 5, the smoothing capacitor 3 uses the energy supplied from the outside. Since the discharge cannot be performed, the voltage of the smoothing capacitor 3 is overcharged to a voltage higher than the peak value of the AC power supply 1 and becomes a high voltage, and there is a problem that the components in the inverter device are damaged due to overvoltage.

  The above is the case where there is no circuit that discharges the smoothing capacitor of the inverter device when the motor is stopped. However, even if a load such as a control power supply is taken from the smoothing capacitor, the same smoothing is required for a very light load. Capacitor overcharge is likely to occur.

  In the circuit shown in FIG. 9, even when there is no AC reactor 40 for power factor improvement, a transformer for voltage conversion is provided between the impedance of the wiring or between the AC power source 1 and the line capacitor 41. In some cases, resonance occurs between the impedance of the transformer and the line capacitor 41, and the smoothing capacitor 3 may be overcharged and become a high voltage as described above.

  On the other hand, even when the regenerative converter 50 is not connected, when a device configured with a semiconductor switch or the like that sharply distorts the power supply voltage is connected to the same AC power supply 1 as the motor drive inverter device, Similar problems may occur.

  The present invention has been made in view of the above, and when all of the switching elements constituting the voltage type inverter are controlled to be in the OFF state, the terminal voltage is maintained even when the smoothing capacitor is overcharged. An object of the present invention is to obtain an inverter device for driving an electric motor provided with a mechanism for suppressing the ascent.

  In order to achieve the above-described object, the present invention provides a rectifier that rectifies an AC voltage, a smoothing capacitor that smoothes a DC voltage output from the rectifier, and a main circuit voltage that appears at both ends of the smoothing capacitor. And a voltage-type inverter that generates an AC voltage to be applied to the motor by operation. When the semiconductor switching element that constitutes the voltage-type inverter stops switching operation, both ends of the smoothing capacitor And a control means for causing the semiconductor switching elements constituting the voltage-type inverter to perform a switching operation so that a current flows through the electric motor when the main circuit voltage appearing in is higher than a threshold voltage.

  According to the present invention, when all of the switching elements constituting the voltage type inverter are controlled to be in the OFF state, resonance between the line capacitor provided in the AC input stage and the reactor, or the AC voltage is excessive surge voltage. When an overvoltage occurs due to the superimposition of the capacitor and the smoothing capacitor is overcharged, the semiconductor switching element that constitutes the voltage type inverter performs a switching operation so that a current flows to the motor. Charging energy is consumed due to switching loss of the semiconductor switching element, loss generated in the electric motor, loss in wiring, and the like. Therefore, it is possible to suppress an increase in the terminal voltage of the smoothing capacitor, and it is possible to prevent the components in the inverter device from being damaged due to overvoltage resistance.

  According to the present invention, when all the switching elements constituting the voltage type inverter are controlled to be in the OFF state, an increase in the terminal voltage due to overcharging of the smoothing capacitor is suppressed, and the components in the inverter device are over withstand voltage. There exists an effect that it can prevent damaging.

  Exemplary embodiments of an inverter device for driving a motor according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of an inverter device for driving an electric motor according to Embodiment 1 of the present invention. As shown in FIG. 1, the inverter device for driving an electric motor according to Embodiment 1 includes a rectifier 2 that rectifies an output AC voltage of an AC power supply 1, a smoothing capacitor 3 that smoothes an output DC voltage of the rectifier 2, and a smoothing capacitor 3. In the basic configuration of the voltage type inverter 4 that switches the main circuit voltage appearing at both ends and applies an AC voltage to the motor 5, the main circuit voltage detection circuit 6, the overvoltage suppression start voltage A setting device 7, a comparator 8, an operation command setting device 9, a normal operation gate signal creation circuit 10, a stop overvoltage suppression gate signal creation circuit 11, a gate signal switching circuit 12, and a gate drive circuit 13 are provided.

  The main circuit voltage detection circuit 6 detects the main circuit voltage appearing at both ends of the smoothing capacitor 3 and supplies it to one input terminal (reverse phase input terminal) of the comparator 8. The overvoltage suppression start voltage setting unit 7 can set an overvoltage suppression start voltage. The overvoltage suppression start voltage set by the overvoltage suppression start voltage setting unit 7 is applied to the other input terminal (positive phase input terminal) of the comparator 8. The comparator 8 compares the magnitude relationship between the overvoltage suppression start voltage set by the overvoltage suppression start voltage setter 7 and the main circuit voltage detected by the main circuit voltage detection circuit 6, and shows a binary value indicating the comparison result. Is supplied to the overvoltage suppression gate signal generation circuit 11 at the time of stop.

  The operation command setter 9 can set operation commands such as a start command, a stop command, and a rotation speed command for the electric motor 5. The operation command set by the operation command setting unit 9 is input to the normal operation gate signal generation circuit 10. The normal operation gate signal generation circuit 10 generates a stop determination signal b which is a binary level signal for distinguishing whether the operation command input from the operation command setting unit 9 is a stop command or an operation command other than the stop command. It is generated, and it is output to the overvoltage suppression gate signal generation circuit 11 and the gate signal switching circuit 12 when stopped. At the same time, the normal operation gate signal generation circuit 10 supplies the normal operation to the date electrodes of the switching elements constituting the voltage type inverter 4 in order to drive the motor 5 in accordance with the operation command input from the operation command setter 9. An hour gate signal a is created and output to the gate signal switching circuit 12.

  When the stop overvoltage suppression gate signal generation circuit 11 is at a predetermined logic level indicating that the switching element constituting the voltage type inverter 4 is in the OFF state, the stop determination signal b input from the normal operation gate signal generation circuit 10 On the basis of the output of the comparator 8, a stop overvoltage suppression gate signal c to be applied to the gate electrode of the switching element constituting the voltage type inverter 4 is created and output to the gate signal switching circuit 12.

  Specifically, when the output of the comparator 8 indicates that the main circuit voltage that is the terminal voltage of the smoothing capacitor 3 is larger than the overvoltage suppression start voltage, the stop overvoltage suppression gate signal creation circuit 11 A stop overvoltage suppression gate signal c for controlling the switching elements constituting the voltage type inverter 4 is generated so as to decrease the main circuit voltage by discharging the charged charge of the current. On the other hand, when the output of the comparator 8 indicates that the main circuit voltage is smaller than the overvoltage suppression start voltage, the stop overvoltage suppression gate signal creation circuit 11 turns off all the switching elements constituting the voltage type inverter 4. The stop overvoltage suppression gate signal c to be controlled to the state is created.

  When the logic level of the stop determination signal b indicates an operation command other than the stop command, the gate signal switching circuit 12 selects the normal operation gate signal a created by the gate signal creation circuit 10 and sends it to the gate drive circuit 13. On the other hand, when the logic level of the stop determination signal b indicates a stop command operation command, the stop overvoltage suppression gate signal c created by the stop overvoltage suppression gate signal creation circuit 11 is selected and sent to the gate drive circuit 13. give. The gate drive circuit 13 applies a voltage corresponding to the gate electrode of the switching element constituting the voltage type inverter 4 by the gate signal input from the gate signal switching circuit 12, and sets the voltage type inverter 4 to a desired operation state.

  FIG. 2 is a diagram showing a configuration example in which a regenerative converter is connected in parallel with the motor drive inverter device shown in FIG. In FIG. 2, the regenerative converter connected in parallel is the regenerative converter 50 shown in FIG. 9, and thus the internal configuration is not shown. In the configuration example shown in FIG. 2, the regenerative converter 50 is connected in parallel, and the power factor improvement is performed between the AC power source 1 and the rectifier 2 as a circuit configuration applied to a general motor drive inverter device. An AC reactor 40 is connected, and a line capacitor 41 for noise filter is connected between the lines between the rectifier 2 and the AC reactor 40.

  Also in this configuration, as described with reference to FIG. 9, the regenerative operation of the regenerative converter 50 connected to the AC power supply 1 causes a steep drop in the line voltage at the point A that is the output end of the AC power supply 1. Therefore, this drop voltage resonates between the AC reactor 40 and the line capacitor 41, and the voltage of the line capacitor 41 rises higher than the voltage of the AC power supply 1. Since the voltage higher than the AC power supply 1 generated in the line capacitor 41 is rectified by the rectifier 2 and supplied to the smoothing capacitor 3, the operation for overcharging the smoothing capacitor 3 is similarly performed. .

  However, when the electric motor driving inverter device according to the first embodiment shown in FIG. 1 is used, the voltage rise of the smoothing capacitor 3 can be suppressed. Hereinafter, the operation of the inverter device for driving the motor according to the first embodiment when the line voltage at the point A which is the output terminal of the AC power supply 1 has a steep drop will be described with reference to FIG.

  In FIG. 2, the voltage for starting overvoltage suppression set by the overvoltage suppression start voltage setting unit 7 and the terminal voltage of the smoothing capacitor 3 detected by the main circuit voltage detection circuit 6 are compared by the comparator 8. The comparison result of the magnitude relationship is input to the overvoltage suppression gate signal generation circuit 11 at the time of stop. In addition, operation commands such as a start command, a stop command, and a rotation speed command of the electric motor 5 set by the operation command setting unit 9 are input to the gate signal generation circuit 10 during normal operation.

  When the operation command input from the operation command setter 9 is a stop command, the normal operation gate signal generation circuit 10 generates a “1” level stop determination signal b and is input from the operation command setter 9. When the operation command is a start command other than the stop command, a rotation speed command, or the like, a stop determination signal b of “0” level is generated, and the stop overvoltage suppression gate signal generating circuit 11 and the gate signal switching circuit 12 are connected to each other. Output. Then, the normal operation gate signal generation circuit 10 generates a normal operation gate signal a for driving the electric motor 5 in accordance with the operation command input from the operation command setter 9 and outputs it to the gate signal switching circuit 12. .

  Further, the stop overvoltage suppression gate signal generation circuit 11 is based on the output of the comparator 8 when the stop determination signal b input from the normal operation gate signal generation circuit 10 is at the “1” level. A stop overvoltage suppression gate signal c to be applied to the gate electrode of the switching element constituting the circuit is created and output to the gate signal switching circuit 12.

  FIG. 3 is a flowchart for explaining the operation of the gate signal switching circuit 12. In FIG. 3, the gate signal switching circuit 12 takes in the normal operation gate signal a and the stop determination signal b, which are the outputs of the normal operation gate signal generation circuit 10 (step ST1), and stops the overvoltage suppression gate signal generation circuit at stop. 11 is captured (step ST2), and it is determined whether the stop determination signal b is at "0" level or "1" level (step ST3).

  When the stop determination signal b is “0” level, the gate signal switching circuit 12 selects the normal operation gate signal a fetched from the normal operation gate signal generation circuit 10 (step ST4), and also determines the stop determination. When the signal is “1”, the stop overvoltage suppression gate signal c taken from the stop overvoltage suppression gate signal creation circuit 11 is selected (step ST5), and each is output to the gate drive circuit 13 (step ST6). .

  As a result, the gate drive circuit 13 applies the voltage indicated by the normal operation gate signal a or the stop overvoltage suppression gate signal c output from the gate signal switching circuit 12 to the gate electrode of the switching element constituting the voltage type inverter 4. Then, the voltage type inverter 4 is driven according to the output of the gate signal switching circuit 12.

  Here, when the stop determination signal b input from the normal operation gate signal generation circuit 10 is “1” level, the output of the comparator 8 becomes a negative voltage level. When the main circuit voltage, which is the terminal voltage of the smoothing capacitor 3, is larger than the overvoltage suppression start voltage, the stop overvoltage that controls the switching elements constituting the voltage type inverter 4 so that a current flows through the motor 5. A suppression gate signal c is created.

  That is, when the operation command setter 9 sets all the switching elements constituting the voltage type inverter 4 to the OFF state and the motor 5 is in the stopped state, the resonance phenomenon between the AC reactor 40 and the line-to-line capacitor 41. As a result, the smoothing capacitor 3 is overcharged, and the main circuit voltage, which is the terminal voltage of the smoothing capacitor 3, rises far beyond the peak value of the AC power supply 1, and the rising main circuit voltage is increased by the overvoltage suppression start voltage setting device 7. When the set overvoltage suppression start voltage is exceeded, the switching element of the voltage type inverter 4 is driven so that a current flows through the electric motor 5, so that the loss generated in the switching element of the voltage type inverter 4 and the iron generated in the electric motor 5 The energy of the smoothing capacitor 3 can be discharged due to loss such as loss, copper loss, etc. Is control.

  As a method of controlling the switching element that constitutes the voltage type inverter 4 so that a current flows through the electric motor 5, an overvoltage suppression gate signal at the time of stop that allows the electric current to flow in a state where the electric motor 5 generates as little rotational torque as possible is used. There is a method of generating and a method of generating a stop overvoltage suppression gate signal that allows current to flow while the electric motor 5 generates rotational torque. The former method is advantageous in that it does not affect the load connected to the electric motor 5. For example, there are various methods shown in the following (a) to (c). Of course, in applications where there is no problem even if the electric motor 5 rotates somewhat, it is needless to say that the latter method may be adopted and an electric current may be supplied so that the electric motor 5 rotates. In this case, there is an advantage that the energy of the smoothing capacitor 3 can be discharged also by the shaft output of the electric motor 5 or the like.

  (A) The voltage type inverter 4 is operated so that a substantially direct current flows through the electric motor 5. This is the simplest method. (B) The voltage type inverter 4 is operated so as to alternately switch the energization phase of the current supplied to the electric motor 5. It is possible to prevent the current of the voltage type inverter 4 and the electric motor 5 from being concentrated on one phase. (C) The voltage type inverter 4 is operated so as to supply a high-frequency current to the electric motor 5. This is effective when the electric motor 5 is an induction motor. Hereinafter, a description will be given with reference to FIG.

  FIG. 4 is a diagram showing the relationship between the slip of the induction motor, the torque, and the primary current. As shown in FIG. 4, when the slip is large, a large motor current (1) flows, while the motor torque ( 2) becomes smaller. Therefore, when the electric motor 5 is an induction motor, it can be realized by applying a high-frequency current in a state where a high-frequency voltage is applied and the slip is increased to reduce the motor torque. According to this, the current of the voltage type inverter 4 and the electric motor 5 becomes equal to three phases, and the loss is distributed to the three phases, so that the reliability is further improved.

  On the other hand, when the stop determination signal b input from the normal operation gate signal generation circuit 10 is “1” level, the over-voltage suppression gate signal generation circuit 11 at the time of stop becomes an overvoltage when the output of the comparator 8 becomes a positive voltage level. When the main circuit voltage that is the terminal voltage of the smoothing capacitor 3 is smaller than the overvoltage suppression start voltage set by the suppression start voltage setting unit 7, the main circuit voltage need not be suppressed. 4 generates a stop overvoltage suppression gate signal c that turns off all of the switching elements constituting the circuit 4.

  In the case where the operation command other than the stop command is set by the operation command setting unit 9 and the motor 5 is driven by the normal operation gate signal a from the normal operation gate signal generation circuit 10, The operation is the same as in the case of using the motor drive inverter device. That is, the smoothing capacitor 3 due to the resonance of the AC reactor 40 and the line-to-line capacitor 41 is caused by the loss generated in the switching element of the voltage type inverter 4, the loss such as iron loss or copper loss generated in the motor 5, and the shaft output of the motor 5. The charged power is not consumed and the smoothing capacitor 3 is not overcharged, and the operation of the electric motor 5 set by the operation command setter 9 is not affected.

  As described above, according to the first embodiment, when the stop command is set as the operation command by the operation command setting device 9, the smoothing capacitor 3 is switched to AC by the resonance phenomenon between the AC reactor 40 and the line-to-line capacitor 41. Since overcharging exceeding the peak value of the power supply 1 is suppressed, it is possible to prevent the components inside the inverter device from being damaged due to overvoltage resistance.

  In FIG. 1 and FIG. 2, the characteristics of the stop overvoltage suppression gate signal c created by the stop overvoltage suppression gate signal creation circuit 11 are defined using the comparator 8, but the present invention is limited to this configuration. Any configuration may be used as long as it can create a gate signal that can suitably suppress the overvoltage of the smoothing capacitor 3 by the stop overvoltage suppression gate signal creation circuit 11.

Embodiment 2. FIG.
5 is a block diagram showing a configuration of an inverter device for driving an electric motor according to Embodiment 2 of the present invention. In FIG. 5, the same reference numerals are given to components that are the same as or equivalent to the components shown in FIG. 1 (Embodiment 1). Here, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 5, the inverter device for driving a motor according to the second embodiment includes a rectifier 2 that rectifies the output AC voltage of the AC power supply 1, a smoothing capacitor 3 that smoothes the output DC voltage of the rectifier 2, and a smoothing capacitor 3. In the basic configuration of the voltage type inverter 4 that switches the main circuit voltage appearing at both ends and applies an AC voltage to the electric motor 5, the operation command setter 9, the normal operation gate signal are used as a configuration for controlling the voltage type inverter 4. A creation circuit 10, a gate drive circuit 13, a resistor 60, a switch 61, and a switch control circuit 62A are provided.

  The resistor 60 is provided between one output terminal of the rectifier 2 and a corresponding terminal of the smoothing capacitor 3. The switch 61 is a switch element such as a contactor or a thyristor, and is arranged so as to short-circuit / non-short-circuit both ends of the resistor 60 under the control of the switch control circuit 62A. In many cases, the resistor 60 and the switch 61 are mounted in advance as a circuit that operates only when the power is turned on in order to suppress the inrush current to the smoothing capacitor 3. It is.

  As described in the first embodiment, the normal operation gate signal generation circuit 10 outputs the stop determination signal b of “1” level when the operation command input from the operation command setter 9 is a stop command. When the operation command created and input from the operation command setting unit 9 is a start command other than the stop command, a rotation speed command, or the like, the stop determination signal b of “0” level is generated. The stop determination signal b is supplied to the switch control circuit 62A.

  Further, as described in the first embodiment, the normal operation gate signal generation circuit 10 generates the normal operation gate signal a for driving the motor 5 in accordance with the operation command input from the operation command setting unit 9. In the second embodiment, the gate signal a during normal operation is directly supplied to the gate drive circuit 13.

  The switch control circuit 62A controls the switch 61 to be in an open circuit state when the stop determination signal b from the gate signal generation circuit 10 during normal operation is “1” level, and the current from the rectifier 2 is limited by the resistor 60. In the case where the smoothing capacitor 3 is charged and the stop determination signal is “0” level, the switch 61 is controlled to be closed, the resistor 60 is short-circuited, and the current from the rectifier 2 is limited. The smoothing capacitor 3 operates without being charged.

  In the inverter device for driving a motor according to the second embodiment configured as described above, even when the AC reactor 40, the line-to-line capacitor 41, and the regenerative converter 50 shown in FIG. In response to the stop command, the switching element of the voltage type inverter 4 is completely cut off and no voltage or current is supplied to the motor 5, so that the smoothing capacitor 3 is excessive due to the resonance phenomenon between the AC reactor 40 and the line capacitor 41. It is possible to suppress the terminal voltage from greatly exceeding the peak value of the AC power supply 1 by being charged.

  That is, when the stop command from the operation command setting unit 9 is set, the switching element of the voltage type inverter 4 is completely cut off, and in the state where no voltage or current is supplied to the motor 5, the gate signal generation circuit 10 during normal operation is The stop determination signal b of “1” level is output to the switch control circuit 62A. When the stop determination signal is “1” level, the switch control circuit 62A controls the switch 61 to be in an open circuit state, so that the resistor 60 is interposed between the rectifier 2 and the smoothing capacitor 3. Become.

  Accordingly, the output terminal voltage of the AC power supply 1 is distorted due to the operation of the regenerative converter 50, etc., which resonates between the AC reactor 40 and the line capacitor 41 and becomes higher than the voltage of the AC power supply 1 and is smoothed from the rectifier 2. Even if an excessive charging current tries to flow through the capacitor 3, the resistor 60 limits the charging current, so that the voltage increase of the smoothing capacitor 3 can be suppressed.

  Since the smoothing capacitor 3 is usually provided with a circuit for discharging even though the power consumption is small for voltage detection or the like, if the overcharge to the smoothing capacitor 3 can be limited by the resistor 60, the smoothing capacitor 3 Therefore, it is possible to prevent the terminal voltage of the inverter device from rising above a certain level, and it is possible to prevent the internal components of the inverter device from being damaged due to excessive breakdown voltage.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing a configuration of an inverter device for driving an electric motor according to Embodiment 3 of the present invention. In FIG. 6, components that are the same as or equivalent to the components shown in FIG. 1 (Embodiment 1) and FIG. 5 (Embodiment 2) are assigned the same reference numerals. Here, the description will be focused on the portion related to the third embodiment.

  As shown in FIG. 6, the inverter device for driving an electric motor according to the third embodiment includes a rectifier 2 that rectifies the output AC voltage of the AC power supply 1, a smoothing capacitor 3 that smoothes the output DC voltage of the rectifier 2, and a smoothing capacitor 3. FIG. 5 (Embodiment 2) shows a configuration for controlling the voltage type inverter 4 in the basic configuration of the voltage type inverter 4 that switches the main circuit voltage appearing at both ends of the circuit and applies an AC voltage to the motor 5. In the configuration, a switch control circuit 62B is provided instead of the switch control circuit 62A, and the main circuit voltage detection circuit 6, the overvoltage suppression start voltage setting device 7 and the comparator 8 shown in FIG. 1 (Embodiment 1) are provided. Is provided.

  The switch control circuit 62B compares the magnitude relationship between the voltage for starting overvoltage suppression set by the overvoltage suppression start voltage setting unit 7 and the terminal voltage of the smoothing capacitor 3 detected by the main circuit voltage detection circuit 6. An output signal from the comparator 8 is input, and a stop determination signal b is input from the gate signal generation circuit 10 during normal operation, and the switch 61 is controlled based on both signals.

  That is, when the terminal voltage of the smoothing capacitor 3 is higher than the voltage for starting the overvoltage suppression set by the overvoltage suppression start voltage setting unit 7 and the stop determination signal b is at the “1” level. Similarly to the switch control circuit 62A, the switch 61 is controlled to be in an open circuit state, and the resistor 60 is interposed between the rectifier 2 and the smoothing capacitor 3.

  Here, in the second embodiment, when the stop determination signal b changes from “1” level to “0”, the switch control circuit 62A changes the switch 61 from the open circuit state to the closed circuit state. While the switch 61 is open, the power input from the AC power supply 1 to the smoothing capacitor 3 is restricted by the resistor 60, so that the voltage of the smoothing capacitor 3 decreases and the output of the electric motor 5 is output. May be reduced.

  On the other hand, in the third embodiment, if the set voltage in the overvoltage suppression start voltage setting unit 7 is set higher than the voltage of the AC power supply 1, the switch 61 causes the terminal voltage of the smoothing capacitor 3 to be overvoltage suppressed. The circuit is opened when the voltage is higher than or equal to the voltage set by the start voltage setter 7, and the circuit is closed when the voltage is lower than that. Therefore, the voltage shortage of the smoothing capacitor 3 at the start of operation can be suppressed while suppressing the voltage rise of the smoothing capacitor 3. There is a new effect.

Embodiment 4 FIG.
FIG. 7 is a block diagram showing a configuration of an inverter device for driving an electric motor according to Embodiment 4 of the present invention. In FIG. 7, the same reference numerals are given to components that are the same as or equivalent to the components shown in FIG. 1 (Embodiment 1). Here, the description will be focused on the portion related to the fourth embodiment.

  As shown in FIG. 7, the inverter device for driving a motor according to the fourth embodiment includes a rectifier 2 that rectifies the output AC voltage of the AC power supply 1, a smoothing capacitor 3 that smoothes the output DC voltage of the rectifier 2, and a smoothing capacitor 3. FIG. 1 (Embodiment 1) shows a configuration for controlling the voltage type inverter 4 in the basic configuration with the voltage type inverter 4 that switches the main circuit voltage appearing at both ends of the inverter and applies an AC voltage to the motor 5. In the configuration, a stop overvoltage level setter 70 is provided instead of the overvoltage suppression start voltage setter 7, a stop overvoltage detection circuit 71 is provided instead of the stop overvoltage suppression gate signal creation circuit 11, and a gate signal The switching circuit 12 is deleted.

  When the stop determination signal b from the normal operation gate signal generation circuit 10 is “1” level, the stop overvoltage detection circuit 71 has a negative voltage level at the output of the comparator 8 and the terminal voltage of the smoothing capacitor 3 is When the voltage is higher than the voltage set by the stop overvoltage level setting unit 70, the power supply voltage distortion is assumed to be large, and the stop overvoltage abnormal signal d is output to the outside.

  According to this configuration, it can be determined from the outside that the distortion of the power supply system voltage that is the output terminal voltage of the AC power supply 1 has become very large. For example, the power supply of the system is shut off or connected to the same power supply system It is possible to take measures to reduce voltage distortion, such as disconnecting the regenerative converter that is connected to another system, and other devices connected to the same system may be overvoltaged due to voltage distortion at the same time. There is an effect that it is possible to suppress the occurrence.

  Here, although not shown, the rectifier 2 that rectifies the output AC voltage of the AC power supply 1, the smoothing capacitor 3 that smoothes the output DC voltage of the rectifier 2, and the main circuit voltage that appears across the smoothing capacitor 3 are switched. In the basic configuration of the voltage type inverter 4 that applies the AC voltage to the electric motor 5, the configuration of controlling the voltage type inverter 4 can be configured by combining the first, third, and fourth embodiments.

  According to this configuration, when the stop overvoltage suppression gate signal creation circuit 11, the gate signal switching circuit 12 and the switch control circuit 62B are operated so as to suppress the voltage rise of the smoothing capacitor 3, the stop overvoltage abnormality is externally provided. Since the signal d can be output, it is possible to take an external measure after reliably suppressing the overvoltage, and it is possible to reliably prevent the internal components of the inverter device from being damaged due to excessive breakdown voltage. There is.

  Although the first to fourth embodiments have been described with the AC reactor 40 for power factor improvement in mind, even if there is no AC reactor 40 for power factor improvement, wiring impedance and When a transformer for voltage conversion is provided between the AC power supply 1 and the line capacitor 41, resonance occurs between the impedance of the transformer and the line capacitor 41, so that the smoothing capacitor 3 is overcharged and the terminal Although the voltage may be high, even in this case, according to the present invention, since the overvoltage of the smoothing capacitor 3 can be suppressed, the same effects as those of the first to fourth embodiments are obtained.

  Moreover, although Embodiment 1-4 demonstrated the case where the regenerative converter was connected in parallel, even when the regenerative converter is not connected, the apparatus comprised by a semiconductor switch etc. which distorts a power supply voltage sharply is demonstrated. When connected to the same AC power source, the voltage distortion similarly increases the terminal voltage of the smoothing capacitor 3 due to the resonance phenomenon between the AC reactor 40 and the line capacitor 41. According to the present invention, the smoothing capacitor 3 can be suppressed, and in this case as well, the same effects as those of the first to fourth embodiments are obtained.

  Furthermore, a phenomenon in which a voltage larger than the voltage peak value of the AC power supply 1 such as a surge voltage superimposed on the commercial voltage component of the AC power supply 1 is transiently generated continuously or discontinuously, and the smoothing capacitor 3 is overcharged. Needless to say, the present invention can be applied to the above.

  In short, the present invention does not presuppose the presence of the AC reactor 40, the line-to-line capacitor 41, and the regenerative converter 50 shown in FIG. 2, but the switching elements constituting the voltage type inverter 4 regardless of the presence or absence thereof. Is applied to effectively suppress the voltage rise when the terminal voltage of the smoothing capacitor 3 rises above the voltage peak value of the AC power supply 1 when the gate is cut off and no voltage is applied to the motor 5. The

  In the application of the present invention, unlike the overvoltage suppression start voltage setting unit 7 described in the first embodiment, it is not necessary to set a voltage for starting the overvoltage suppression operation in advance. For example, it is possible to adopt various modifications such as detecting a voltage with the power supply voltage distortion removed by a CR filter or the like, and adding an offset to the voltage to start an overvoltage suppression operation. It goes without saying that all are included in the scope of the present invention.

  As described above, the inverter device for driving the motor according to the present invention is useful when operating the motor in a situation where an excessive voltage is generated in the AC input stage, and in particular, the regenerative converter is connected in parallel to the same power supply system. Suitable for

It is a block diagram which shows the structure of the inverter apparatus for motor drive by Embodiment 1 of this invention. It is a figure which shows the structural example which connected the regenerative converter in parallel with the inverter apparatus for motor drive shown in FIG. 3 is a flowchart for explaining the operation of the gate signal switching circuit shown in FIG. 1. It is a figure which shows the relational characteristic of the slip of an induction motor, a torque, and a primary current. It is a block diagram which shows the structure of the inverter apparatus for motor drive by Embodiment 2 of this invention. It is a block diagram which shows the structure of the inverter apparatus for motor drive by Embodiment 3 of this invention. It is a block diagram which shows the structure of the inverter apparatus for motor drive by Embodiment 4 of this invention. It is a figure which shows the structural example of the conventional inverter apparatus for motor drive. It is a figure which shows the structural example which connected the regenerative converter in parallel with the inverter apparatus for motor drive shown in FIG. It is a figure explaining the regenerative current which flows into the alternating current power supply side from a regenerative converter in FIG. It is a figure explaining the state of the line voltage in A point shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier 3 Smoothing capacitor 4 Voltage type inverter 5 Electric motor 6 Main circuit voltage detection circuit 7 Overvoltage suppression start voltage setting device 8 Comparator 9 Operation command setting device 10 Gate signal preparation circuit at normal operation 11 Overvoltage suppression gate signal at stop Creation circuit 12 Gate signal switching circuit 13 Gate drive circuit 60 Resistor 61 Switch 60A, 60B Switch control circuit 70 Overvoltage level setter at stop 71 Overvoltage detection circuit at stop

Claims (11)

A rectifier that rectifies an AC voltage, a smoothing capacitor that smoothes a DC voltage output from the rectifier, and a voltage type that converts a main circuit voltage appearing at both ends of the smoothing capacitor into an AC voltage applied to an electric motor by a switching operation of a semiconductor switching element. In an inverter device for driving an electric motor comprising an inverter,
When the main circuit voltage appearing at both ends of the smoothing capacitor is higher than a threshold voltage when the semiconductor switching element that constitutes the voltage type inverter has stopped switching operation, the current is supplied to the electric motor. Control means for causing a semiconductor switching element constituting the voltage type inverter to perform a switching operation;
An inverter device for driving an electric motor. The control means includes
A configuration for controlling a switching operation of a semiconductor switching element constituting the voltage type inverter so as to apply a voltage to the motor such that the motor hardly rotates,
The inverter device for driving a motor according to claim 1, comprising: The control means includes
A configuration for controlling a switching operation of a semiconductor switching element that constitutes the voltage type inverter so as to supply a current that is substantially DC to the electric motor;
The inverter device for driving an electric motor according to claim 2, comprising: The control means includes
A configuration for controlling a switching operation of a semiconductor switching element that constitutes the voltage type inverter so as to alternately switch an energization phase of a current supplied to the electric motor;
The inverter device for driving an electric motor according to claim 2, comprising: The control means includes
A configuration for controlling a switching operation of a semiconductor switching element constituting the voltage type inverter so as to supply a high-frequency current to the electric motor;
The inverter device for driving an electric motor according to claim 2, comprising: A rectifier that rectifies an AC voltage, a smoothing capacitor that smoothes a DC voltage output from the rectifier, and a voltage type that converts a main circuit voltage appearing at both ends of the smoothing capacitor into an AC voltage applied to an electric motor by a switching operation of a semiconductor switching element. In an inverter device for driving an electric motor comprising an inverter,
Provided between the rectifier and the smoothing capacitor, a parallel circuit of a resistor and a switch element capable of setting both ends of the resistor in a short-circuited state and a non-short-circuited state;
Means for causing the switch element to perform an open circuit operation when the semiconductor switching element constituting the voltage type inverter has stopped switching operation;
An inverter device for driving an electric motor. A rectifier that rectifies an AC voltage, a smoothing capacitor that smoothes a DC voltage output from the rectifier, and a voltage type that converts a main circuit voltage appearing at both ends of the smoothing capacitor into an AC voltage applied to an electric motor by a switching operation of a semiconductor switching element. In an inverter device for driving an electric motor comprising an inverter,
Provided between the rectifier and the smoothing capacitor, a parallel circuit of a resistor and a switch element capable of setting both ends of the resistor in a short-circuited state and a non-short-circuited state;
When the semiconductor switching element constituting the voltage type inverter stops switching operation, when the main circuit voltage appearing at both ends of the smoothing capacitor becomes higher than a threshold voltage, the switching element is caused to perform an open circuit operation. Means,
An inverter device for driving an electric motor.   8. The inverter apparatus for driving a motor according to claim 6, wherein the parallel circuit is an inrush prevention suppressing circuit provided in advance to suppress an inrush current to the smoothing capacitor. A rectifier that rectifies an AC voltage, a smoothing capacitor that smoothes a DC voltage output from the rectifier, and a voltage type that converts a main circuit voltage appearing at both ends of the smoothing capacitor into an AC voltage applied to an electric motor by a switching operation of a semiconductor switching element. In an inverter device for driving an electric motor comprising an inverter,
When the semiconductor switching element constituting the voltage type inverter has stopped switching operation, when the main circuit voltage appearing at both ends of the smoothing capacitor becomes higher than the threshold voltage, an overvoltage abnormal state at the time of stop has occurred. Means for informing the outside,
An inverter device for driving an electric motor. When the semiconductor switching element constituting the voltage type inverter has stopped switching operation, when the main circuit voltage appearing at both ends of the smoothing capacitor is higher than the threshold voltage, an overvoltage abnormal state at the time of stop has occurred. Means for informing the outside,
The inverter device for driving an electric motor according to claim 1, comprising: When the semiconductor switching element constituting the voltage type inverter has stopped switching operation, when the main circuit voltage appearing at both ends of the smoothing capacitor is higher than the threshold voltage, an overvoltage abnormal state at the time of stop has occurred. Means for informing the outside,
An inverter device for driving an electric motor according to claim 7, comprising:

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