JP4882648B2 - Dynamic brake device - Google Patents

Description

  The present invention relates to a dynamic brake device that absorbs regenerative power of an electric motor with a resistor, and more particularly to parallel operation control of a plurality of brake units.

  In a device that drives an AC motor with a voltage source inverter, there is a dynamic brake (DBR) method as a method for absorbing regenerative power from the motor. In order to reduce the size of the equipment and increase the power absorption capacity of this dynamic brake device, a method of installing a plurality of units (a plurality of units) in parallel and performing the parallel operation is often employed.

  FIG. 3 shows the circuit configuration of two inverter devices with dynamic brake devices. The main circuit of the inverter device converts alternating current power into direct current power by the rectifier 1 and the smoothing capacitor 2, obtains alternating current power whose voltage and frequency are controlled by the voltage source inverter 3 using this as a direct current power source, and an electric motor (IM) as a load Drive).

  The main circuit of the dynamic brake device has a configuration in which semiconductor switches 5A and 5B are connected in series to two resistors 4A and 4B, respectively, and these are connected in parallel to the DC circuit of the inverter device. The control circuit of the dynamic brake device includes a DC voltage detection unit 6 that detects whether or not the DC voltage of the inverter device exceeds the set voltage V, and a gate control unit 7 that controls on / off of the switches 5A and 5B with this detection signal. When the DC voltage exceeds the set voltage V due to regenerative operation of the motor, etc., the switches 5A and 5B are turned on, the regenerative power is absorbed as heat by the resistors 4A and 4B, and the overvoltage trip of the inverter device is prevented. To do.

  As a control method for such a dynamic brake device, if the set voltage V in the DC voltage detection unit 7 is set to a high value, absorption of regenerative power is delayed, and if it is set to a low value, wasteful power consumption occurs. Is set high and is lowered for a predetermined time when the motor is stopped or a deceleration command is detected (for example, see Patent Document 1).

Further, as a protection method for the resistors 4A and 4B, there is one that prevents the resistor from overheating by detecting the temperature of the resistor with a sensor or estimating the absorbed power (see, for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 05-015180 JP 2003-333873 A

  In the dynamic brake device, an overvoltage trip of the inverter device can be prevented by applying the control method of Patent Document 1 in which the set voltage V of the DC voltage detector 6 is variable. Further, the protection method of Patent Document 2 can be applied to protect the resistor from overheating.

  When the above control method and protection method are applied to a dynamic brake device having a multi-unit configuration, if the DC voltage detection unit 6 and the gate control unit 7 are provided for each unit, the DC voltage detection error between the units and the semiconductor switch Due to a shift in the control timing, an imbalance occurs in the energization period of each resistor, and the resistor having a long energization period may be overheated or burned.

  As a countermeasure, when the DC voltage detection unit 6 and the gate control unit 7 are configured to perform DC voltage detection and gate control of both semiconductor switches in parallel, a configuration between the gate control unit 7 and the semiconductor switches 5A and 5B is adopted. As a result, the length of the signal cable for connecting the semiconductor switches 5A and 5B may cause the semiconductor switches 5A and 5B to be erroneously turned on due to noise or the like induced from the main circuit current of the inverter device. In this case, the resistor is overheated or wasteful power is consumed, or the inverter device is stopped.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic brake device that can perform reliable load balance operation of each unit and prevent malfunction due to noise or the like in a dynamic brake device that performs DC voltage detection and gate control for each unit.

  In order to solve the above-mentioned problem, the present invention gradually increases the ON level setting value of a unit when a unit starts power absorption operation, thereby making it higher than the ON level setting value of other units. The load balance operation is performed by sequentially switching the power absorption operation by each unit, in which other units with low level setting values start power absorption operation and gradually increase their ON level setting values. It is characterized by.

(1) The regenerative power of the motor is absorbed by the parallel operation control of a plurality of brake units connected in parallel to the DC circuit, and the resistor and the switch are connected in series, so that the DC voltage of the DC circuit is detected and the switch is turned on. Is a dynamic brake device for each brake unit,
Each control unit provided for each brake unit controls to turn on the switch when the DC voltage detection value exceeds the ON level setting value and gradually increases the ON level setting value. A control circuit for turning off the switch when the ON level set value or less is provided is provided.

(2) the respective control unit, said ON level setpoint time to gradually increase the number brake unit carriage with respect to time to gradually increase the ON level setting value when configuring with a single brake unit fraction It is characterized by.

  As described above, according to the present invention, in a dynamic brake device that performs DC voltage detection and gate control for each unit, when a certain unit starts power absorption operation, the ON level set value is gradually increased to increase the other unit. Control of sequential switching of power absorption operation by each unit such that other units with lower ON level setting value start power absorption operation and gradually increase the ON level setting value. As a result, each unit can be reliably load-balanced, and can be prevented from malfunctioning due to noise or the like.

  FIG. 1 is a configuration diagram of a dynamic brake device showing an embodiment of the present invention, and a different part from FIG. 3 is a control circuit of the dynamic brake device.

  This control circuit is provided with two control units 8A and 8B for each unit, and individually controls the semiconductor switches 5A and 5B. The control units 8A and 8B include DC voltage detection circuits 11A and 11B, ON level detectors 12A and 12B, ON time counters 13A and 13B, ON level adjusters 14A and 14B, and gate output circuits 15A and 15B. To do.

  The DC voltage detection circuits 11A and 11B detect the DC voltage of the inverter device. The ON level detectors 12A and 12B generate ON / OFF gate signals according to whether or not the detected value of the DC voltage exceeds the ON level set value. The ON time counters 13A and 13B perform time counting after an initial reset when the ON level detectors 12A and 12B generate an ON gate signal.

  The ON level adjusters 14A and 14B adjust the ON level set values of the ON level detectors 12A and 12B. When the ON time counters 13A and 13B start time counting, the ON level adjusters 14A and 14B have a preset lower limit voltage. The voltage is gradually increased to the upper limit voltage with a predetermined function characteristic (for example, a linear function increasing at a constant slope with respect to time). Further, when the ON time counters 13A and 13B stop the time count, the ON level adjusters 14A and 14B gradually increase the ON level set value by a time twice as long as this time count, and the ON level of the other unit. A value higher than the set value is secured and the ON level detection operation is stabilized.

  The gate output circuits 15A and 15B perform on / off control of the semiconductor switches 5A and 5B, respectively, according to the on / off detection signals obtained from the ON level detectors 12A and 12B.

  The control operation of the dynamic brake device having the above configuration will be described. First, during operation of the inverter device, the DC voltage detection circuits 11A and 11B detect this DC voltage, including the case where the DC voltage rises due to regenerative power from the load side. When this detection voltage becomes equal to or higher than a reference value (initial ON level setting value) set in the ON level detectors 12A and 12B, an on-gate signal is output from the gate output circuits 15A and 15B to the semiconductor switches 5A and 5B, and the resistance Absorption of regenerative power by the devices 4A and 4B is started.

  In this control, the ON time counters 13A and 13B start counting time from the time when the ON level detectors 12A and 12B generate the ON gate signal, and the ON level adjusters 14A and 14B turn ON the ON level detectors 12A and 12B. When the level set value is increased with time, and the ON level set value becomes equal to or greater than the DC voltage detection value, the ON level detectors 12A and 12B generate an off gate signal, and the gate output circuits 15A and 15B receive the semiconductor switch 5A. 5B is turned off, and regenerative power absorption by the resistors 4A and 4B is stopped.

  Therefore, the control operation when the DC voltage exceeds the ON level set value is as shown in FIG. 2, when both units alternately repeat the on / off control of the semiconductor switches 5A and 5B, and the regenerative power is large. Both units keep on-control to suppress the DC voltage rise.

  FIG. 2 shows a case where the control unit 8A first detects an increase in DC voltage and starts power absorption by the resistor 4A. When the control unit 8B stops the power absorption by the resistor 4A, the DC voltage starts to increase. Power absorption is started by the resistor 4B. In the stop of power absorption by the resistor 4B, alternating power absorption and stop of starting power absorption by the resistor 4A are repeated.

  Therefore, in the ON level detectors 12A and 12B, even when the ON level set value has a deviation, the ON level detector that detects the DC voltage rise first starts the power absorption operation and the ON level set value is Increased ON level adjustment is performed, and the other ON level detector can detect a DC voltage rise to perform power absorption control, thereby obtaining operation control in which the loads of both units are balanced. Further, even when noise or the like is superimposed on the detection signals of the DC voltage detection circuits 11A and 11B, it is possible to obtain operation control in which both units operate alternately to balance the load. Also, even when the ON level initial value (reference value) is set high, regenerative power can be quickly absorbed by the cooperation of both units, preventing malfunction of each unit due to noise, etc., and wasteful power consumption. It can be lost.

In addition, although the case where it is set as the structure of two dynamic brake units is shown in embodiment, it can apply to the unit structure of three or more units, and can obtain an equivalent effect. In this case, for example, in the configuration of three units, the ratio of the power absorption time to the stop time by each unit is tripled, and the time for gradually increasing the ON level set value is the above-described case of configuring with one brake unit. By setting the time to gradually increase the ON level set value to 1 / the number of brake units, it is possible to obtain a load balance operation in which the power absorption operation by each unit is sequentially switched.

  Moreover, although the case where a dynamic brake device is provided in the DC circuit of the inverter device is shown in the embodiment, the present invention can be applied to a separate configuration separated from the inverter device or a dedicated dynamic brake device for an AC motor.

The block diagram of the dynamic brake device which shows embodiment of this invention. The control waveform figure in embodiment. The circuit block diagram of two inverter apparatuses with a dynamic brake apparatus.

Explanation of symbols

4A, 4B Resistor 5A, 5B Semiconductor switch 8A, 8B Controller 11A, 11B DC voltage detector 12A, 12B ON level detector 13A, 13B ON time counter 14A, 14B ON level adjuster 15A, 15B Gate output circuit

Claims (2)

The regenerative power of the motor is absorbed by the parallel operation control of a plurality of brake units connected in parallel to the DC circuit, and the resistor and the switch are connected in series, and the DC voltage detection of the DC circuit and the ON control of the switch are controlled by each brake. A dynamic brake device for each unit,
Each control unit provided for each brake unit controls to turn on the switch when the DC voltage detection value exceeds the ON level setting value and gradually increases the ON level setting value. A dynamic brake device comprising a control circuit for controlling the switch to be turned off when the ON level is lower than a set value. Wherein each control unit includes a time to gradually increase the ON level setting value, to the brake unit carriage fraction against time to gradually increase the ON level setting value when configuring with a single brake unit The dynamic brake device according to claim 1.

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