JP2006115667A - Surge voltage suppressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surge voltage suppressor capable of preventing load insulation deterioration from an excessive surge voltage, reducing loss, reducing size and weight.
A rectifier circuit 11 comprising a three-phase diode bridge DB1 and a smoothing capacitor C1 is connected to an input terminal of an electric motor 2 driven by a PWM inverter 1, and a capacitor C1 is connected to the positive side of the output of the rectifier circuit 11. The gate drive circuit 12 connects the drain terminal of the voltage control transistor Q1 via the discharge resistor R1, connects the source terminal to the negative side, and drives the gate of the voltage control transistor Q1 by the output voltage of the rectifier circuit 11. Is provided.
[Selection] Figure 1

Description

  The present invention relates to a surge voltage suppressing device that suppresses a surge voltage to an electric motor driven by a PWM inverter.

  When a cable connecting a voltage type PWM (pulse width modulation) inverter and a motor as a load becomes a long wiring, reflection occurs at the load end due to a steep pulse voltage fluctuation of the inverter, and an excessive surge voltage is generated. If this surge voltage exceeds the withstand voltage of the load, a short circuit accident may occur, and in some cases, a fire may occur.

Conventionally, in order to suppress the surge voltage, for example, a filter is connected between an inverter and a load, and a steep pulse fluctuation generated in the inverter is suppressed by this filter.
It has also been proposed to absorb a surge voltage by connecting a filter (voltage suppression device) composed of a resistor and a capacitance to an input terminal of a load (see, for example, Patent Document 1).
JP-A-8-23682

  As described above, when a filter is connected between the inverter and the load, since a large load current flows through the filter, there is a problem that the capacity of the filter increases and the weight and dimensions increase. In addition, when a filter composed of a resistor and a capacitance is connected to the input terminal of the load, the DC intermediate voltage of the inverter is always applied to the discharging resistor during the load operation, resulting in a large resistance loss. There was a problem. In order to avoid this resistance loss, a cable for energy regeneration is required separately from the load power line.

  The present invention has been made in view of the above points, and is a surge voltage suppressing device that can prevent load insulation deterioration from an excessive surge voltage, has a small loss, and can be reduced in size and weight. The purpose is to provide.

  In the present invention, in order to solve the above-mentioned problem, in a surge voltage suppressing device for suppressing a surge voltage to an electric motor driven by a PWM inverter, a rectifier circuit connected to an input terminal of the electric motor, and an output of the rectifier circuit A voltage-controlled transistor having a drain terminal connected to the positive side and a source terminal connected to the negative side; and a gate drive circuit that drives the gate of the voltage-controlled transistor by the output voltage of the rectifier circuit. A featured surge voltage suppression device is provided.

  According to such a surge voltage suppression device, the surge voltage to the electric motor is rectified by the rectifier circuit and supplied to the gate drive circuit, and the voltage control type transistor connected to the rectifier circuit is turned on by this gate drive circuit to make the circuit Therefore, the loss is small, the size and the weight can be reduced, and the insulation deterioration of the load can be prevented.

  The surge voltage suppressor of the present invention includes a rectifier circuit connected to an input terminal of an electric motor, a voltage controlled transistor having a drain terminal connected to the positive side of the output of the rectifier circuit and a source terminal connected to the negative side, and a rectifier By providing a gate drive circuit that drives the gate of the voltage-controlled transistor with the output voltage of the circuit, it is possible to prevent the insulation deterioration of the load from an excessive surge voltage, reducing loss, reducing size and weight. There is an advantage of being able to plan.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a configuration of a surge voltage suppression device according to a first embodiment of the present invention.
In the figure, reference numeral 1 denotes a PWM inverter, which is connected to a three-phase AC drive motor 2 as a load by a long cable 3. A surge voltage suppression circuit 10 for suppressing an excessive surge voltage due to the PWM inverter 1 is connected to the input terminal of the electric motor 2. The surge voltage suppression circuit 10 includes a rectifier circuit 11 including a three-phase diode bridge DB1 and a smoothing capacitor C1, and an input terminal of the electric motor 2 is connected to an AC input terminal of the diode bridge DB1.

  Further, the drain terminal of the voltage control type transistor Q1 is connected to the positive side of the output of the rectifier circuit 11 via the discharging resistor R1 of the capacitor C1, and the source side of the voltage control type transistor Q1 is connected to the negative side. A gate drive circuit 12 drives the gate of the voltage control transistor Q1 and outputs a gate signal to the gate terminal of the voltage control transistor Q1 according to the DC output voltage value of the rectifier circuit 11.

  FIG. 2 is a diagram showing operation waveforms of each part of the surge voltage suppression circuit 10 having the above-described configuration. The input voltage (V) which is the voltage between the motor terminals, the terminal voltage (V) of the capacitor C1, and the gate of the voltage control type transistor Q1. The voltage (V) and the discharge current (A) of the capacitor C1 are shown.

  When the voltage of the capacitor C1 in the surge voltage suppression circuit 10 rises due to the surge voltage generated by the PWM inverter 1 and exceeds the threshold value at time t1, the gate drive circuit 12 generates a gate voltage (gate signal), and the voltage control type The voltage is input to the gate of the transistor Q1 to turn on the voltage control transistor Q1. Thereby, the discharge current of the capacitor C1 flows through the resistor R1 at time t2, and the voltage of the capacitor C1 decreases. When the voltage of the capacitor C1 falls below a certain threshold, the gate voltage of the gate drive circuit 12 is lowered to turn off the voltage control type transistor Q1. At this time, the discharge of the capacitor C1 is completed at the same time.

  In this way, an excessive surge voltage to the electric motor 2 is suppressed, the input voltage of the electric motor 2 becomes equal to or lower than the withstand voltage, and insulation deterioration can be prevented. Here, in the above circuit, since the electric power discharged through the resistor R1 is only the absorption of the surge voltage, the amount of heat generated in the circuit can be reduced, and the loss is small. Therefore, size reduction and weight reduction can be achieved.

  FIG. 3 is a circuit diagram showing the configuration of the surge voltage suppressor according to the second embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same components. In the first embodiment of FIG. 1, the surge voltage is detected by the line voltage, but in the second embodiment, the surge voltage between the ground and the ground voltage is also detected in addition to the line voltage.

  The surge voltage suppression circuit 20 of the present embodiment includes four pairs in which a diode pair (rectifier element) connected to a ground terminal is connected in parallel to a three-phase diode bridge (rectifier element) connected to the input terminal of the electric motor 2. A rectifier circuit 21 having a diode bridge DB2 having a configuration and a smoothing capacitor C2 is provided. The other configuration is the same as that of the first embodiment shown in FIG. 1. A discharge resistor R2 of a capacitor C2 is connected to the positive side of the output of the rectifier circuit 21, and a voltage control type transistor is connected to the other terminal of the resistor R2. The drain terminal of Q2 is connected, the source terminal of the voltage control transistor Q2 is connected to the negative side of the rectifier circuit 21, and the gate of the voltage control transistor Q2 is driven by the gate drive circuit 22 with the DC voltage output value of the rectifier circuit 21. To do.

  Even with such a configuration, as in the first embodiment, the loss is smaller than that of the conventional surge voltage suppression filter, and the size and weight can be reduced, and the insulation deterioration of the load can be prevented. it can.

  FIG. 4 is a circuit diagram showing the configuration of the gate drive circuit of the surge voltage suppressor according to the third embodiment of the present invention. In the third embodiment, only the gate drive circuit is different from the first embodiment and the second embodiment, and the other configurations are the same. Therefore, the surge voltage suppression circuit 10 of FIGS. , Only the circuit configuration corresponding to 20 is shown.

  This circuit has a series circuit of two Zener diodes connected between the positive side and the negative side of the output of the rectifier circuit described above, and the gate of the voltage control type transistor is controlled by the voltage at the connection point of the two Zener diodes. To drive.

  That is, the cathode terminal of the surge voltage suppressing operation Zener diode ZD1 is connected to the positive side of the output of the rectifier circuit via the current limiting resistor R11, and the other anode terminal of the Zener diode ZD1 is connected to the Zener diode ZD2 for generating gate voltage. And the anode terminal of the gate voltage generating Zener diode ZD2 is connected to the negative side of the rectifier circuit, and the gate of the voltage controlled transistor is driven by the gate voltage generating Zener diode ZD2. In FIG. 4, R12 is a gate potential stabilization resistor, T1 is a positive input terminal, T2 is a negative input terminal, and T3 is a gate signal output terminal.

  The Zener voltage of the surge voltage suppressing operation Zener diode ZD1 is set to a surge voltage suppressing operation threshold (for example, 1200 V), and the Zener voltage of the gate voltage generating Zener diode ZD2 is selected to be the gate voltage (for example, 15 V) of the voltage controlled transistor.

  When the voltage between the positive side input terminal T1 and the negative side input terminal T2 exceeds the surge voltage suppression operation threshold value, the Zener diode ZD1 is turned on. Therefore, the Zener diode ZD2 lower than the Zener voltage is also turned on, and the gate signal output terminal T3. A gate voltage is generated at this time, the voltage control type transistor is turned on, and a discharge current of the capacitor flows.

  When the voltage between the positive side input terminal T1 and the negative side input terminal T2 falls below the surge voltage suppression operation threshold, the Zener diode ZD1 does not conduct, and all the voltages between the positive side input terminal T1 and the negative side input terminal T2 are Zener diodes. Take on ZD1. As a result, the voltage between the anode and the cathode of the Zener diode ZD2 becomes zero by the resistor R12, the gate voltage of the gate signal output terminal T3 also becomes zero, the voltage control type transistor is turned off, and the discharge of the capacitor is ended.

  The gate drive circuit having such a configuration is effective for suppressing the surge voltage with respect to the circuit of FIG. 1, and is also effective for the circuit of FIG.

It is a circuit diagram which shows the structure of the surge voltage suppression apparatus of the 1st Embodiment of this invention. It is a figure which shows the operation | movement waveform of each part of the surge voltage suppression circuit of 1st Embodiment. It is a circuit diagram which shows the structure of the surge voltage suppression apparatus of the 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the gate drive circuit of the surge voltage suppression apparatus of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 PWM inverter 2 Electric motor 3 Cable 10,20 Surge voltage suppression circuit 11,21 Rectifier circuit 12,22 Gate drive circuit C1, C2 Smoothing capacitor DB1, DB2 Diode bridge Q1, Q2 Voltage control type transistor R1, R2 Discharge resistance R11 Current limiting resistor R12 Gate potential stabilizing resistor T1 Positive input terminal T2 Negative input terminal T3 Gate signal output terminal ZD1 Zener diode for surge voltage suppression operation ZD2 Zener diode for gate voltage generation

Claims (3)

In the surge voltage suppression device that suppresses the surge voltage to the motor driven by the PWM inverter,
A rectifier circuit connected to the input terminal of the motor;
A voltage controlled transistor having a drain terminal connected to the positive side of the output of the rectifier circuit and a source terminal connected to the negative side;
A gate drive circuit for driving the gate of the voltage-controlled transistor by the output voltage of the rectifier circuit;
A surge voltage suppression device comprising: The rectifier circuit is
The surge voltage suppressing device according to claim 1, wherein a rectifying element connected to the ground terminal is connected in parallel with the rectifying element connected to the input terminal of the electric motor. The gate driving circuit includes:
A series circuit of two Zener diodes connected between the positive side and the negative side of the output of the rectifier circuit;
2. The surge voltage suppressor according to claim 1, wherein a gate of the voltage controlled transistor is driven by a voltage at a connection point of the two Zener diodes.

Images