JPS5820240B2 - Short-circuit protection method for multiple electric motors using inverter drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for protecting motors or branch circuits for motors from short circuits or ground faults when a large number of motors are operated simultaneously by the same impark.

Conventionally, this type of protection methods include (1) installing a current minor loop to detect overcurrent caused by an accident and lowering the output voltage of the impark to reduce current, and (2) completely eliminating the impark by cutting off the gate, etc. (3) a method of coordinating the overload capacity of the innocoator with an overcurrent protection device dedicated to the motor, such as a fuse, etc.

However, method (IX2) is not suitable for applications that require continuous operation, such as in the textile industry, because not only the motor in which the accident occurred but all the motors are stopped.

Therefore, method (3) above is generally adopted, but in this method, the overcurrent protection device dedicated to the motor must be set or selected so that it will not operate at the starting current of the motor, so the overcurrent protection device for each motor must be The disadvantage is that the operating current of the protection device becomes large, and in order to coordinate with this, the inverter must have a large overload capacity.

The present invention eliminates these drawbacks and allows the inverter to coordinate with the operating current of the overcurrent protection device for each motor without stopping the operation of motors other than the motor in the accident (hereinafter referred to as other motors). It is intended to provide a method of financial protection that would otherwise be unnecessary.

Hereinafter, the structure and operation of the present invention will be explained with reference to illustrated embodiments.

The figure is a connection diagram showing an embodiment of the present invention. In the figure, 1 is an inverter main body, 2 is an impark control device that provides a firing signal such as a gate signal or an emitter manual signal to the impark main body 1. This constitutes Impark 1.

3 is a current transformer for overcurrent detection for accident detection; 43 to 4n are overcurrent protection devices for each electric motor such as fuses; and 5a to 5n are electric motors.

In the above configuration, the impark 1 operates upon receiving an ignition signal from the impark control device 2 to the impark main body 1, and drives the electric motors 53 to 5n.

If a short circuit or ground fault occurs in any motor or motor branch circuit during operation, it is detected by the current transformer 3 and the impark 1 is first stopped.

With this N, the fault detection operating current of the current transformer 3 may be set to a value slightly larger by 5 than the sum of the starting current value of the motor with the maximum starting current value and the load current values of other motors. In order to improve the reliability of the thyristor inverter and the reliability of turn-off when the thyristor inverter is stopped, for example, although not shown, this detection circuit is cut off in the inverter control device 2 so that it does not operate only at startup, and the operation setting value is set as described above. It may be lowered below the value.

Further, a detection element such as a current transformer may be provided in each branch circuit of each motor, and detection accuracy may be increased through an OR circuit within the control device 2.

For example, if a short-circuit accident occurs in the electric motor 5n, the inverter 1 will stop.

Then, since the motors other than the motor 5n continue to rotate due to inertia, these motors become generators and supply short-circuit current to the faulty motor 5n.

As a result, the overcurrent protection device 4n of the faulty motor 5n operates, and the faulty motor 5n is automatically disconnected from the line.

Then, if it is detected that the accidental motor 5n has been disconnected from the line and the inverter 1 is restarted, the other motor 58
5(n-1), since the impark stop time is short, the motors continue to rotate due to inertia during the stop, so they can continue to operate without being stopped.

In addition, at this time, the short circuit current to the faulty motor 5n is supplied from another motor as described above, and no current flows to the inverter 1, so the overload capacity of the inverter 1 is determined only by the load capacity and starting capacity of the motor. This eliminates the need for a large reduction in consideration of cooperation with the overcurrent protection devices 4a to 4n of the motor, as in the conventional case.

In this S, the means for detecting the completion of disconnection of the faulty motor from the line is a contact or non-contact signal linked to the operation of the overcurrent protection device of each motor, or a current transformer or voltage relay, etc. is installed in each motor circuit. Then, a method such as guiding those OR signals to the control device 2 and detecting them may be adopted.

In addition, as a means of restarting the inverter, if the inverter is of a type that distributes an ignition signal such as a gate pulse in synchronization with the motor rotor position or induced voltage, the ignition signal distributor If you shut off and turn on the ignition signal on the power supply side to stop or restart, when restarting,
If the rotational speed of the motor has not decreased significantly, it is possible to restart the motor immediately.

If this method alone causes the rotation speed to drop and the restart current to increase, you can restart the inverter by adjusting the DC power supply voltage to the inverter or the impark current advance angle according to the rotation speed. .

In addition, if the inverter is of a type that distributes firing signals such as gate pulses using an oscillator that is unrelated to the rotational speed and rotational position of the motor, the impark frequency should be made to match the frequency that corresponds to the rotational speed of the motor. Just restart Impark.

Furthermore, in the above embodiments, all the motors are operated in parallel, but if the parallel elements of parallel operation include a group of motors that are operated in series or in series-parallel combination, the group of motors can be treated as one parallel element. It is also possible to apply the method of the present invention with this in mind.

In addition, in the above explanation, we have simply referred to "multiple electric motors," but if only electric motors that cannot be used as generators, such as induction motors, direct commutatorless motors that do not have initial excitation means, etc., are operated at the same time, this is true. It is not possible to apply the method of the invention, and mixed operation with these motors and appropriate current sharing for each motor in the event of an accident should be determined through careful consideration at the design stage.

As described above, according to the present invention, when a large number of electric motors are operated simultaneously by the same inverter, even if a short circuit or ground fault occurs, only the failed electric motor can be disconnected from the line without stopping the entire line, and the other electric motors can be operated simultaneously. The inverter can be continuously operated, and the overload capacity of the inverter can be selected to be small, resulting in excellent effects such as cost reduction.

[Brief explanation of drawings]

The figure is a connection diagram showing an embodiment of the present invention. 1... Inverter, 3... Accident detection element, 4a to 4n... Motor overcurrent protection device,
5a-5n...Electric motor.

Claims (1)

[Scope of Claims] 1. In a system in which a large number of electric motors are operated simultaneously by the same impark, all or some of the electric motors are configured in advance to be capable of generating power when the power is turned off, and the total power generation of these motors is The capacity is selected so that if a short circuit or ground fault occurs in any one motor, the overcurrent protection device of the faulty motor circuit can be operated by the generated current from those motors. If a short circuit or ground fault occurs in the circuit on the load side of the branch overcurrent protection device, the detector detects the occurrence of the fault and stops the inverter. As a result, the fault current is transferred to a motor other than the fault motor ( By operating the overcurrent protection device for the faulty motor, only the faulty motor circuit is disconnected from the line, and after detecting the disconnection, the impark is restarted. Start it up and
A short-circuit protection method for multiple motors driven by an inverter, characterized in that other motors continue to operate. 2. A short-circuit protection method for multiple electric motors driven by an inverter, in which a detection element such as a current transformer is provided on the common output bus of the inverter to detect the occurrence of an accident, in the method according to claim 1. 3. A short-circuit protection method for multiple electric motors driven by an inverter, in which a detection element such as a current transformer is provided in each branch circuit of each electric motor to detect the occurrence of an accident, in the method according to claim 1. 4. In the method set forth in claim 1, a detection element such as a current transformer or a voltage relay is provided for each branch circuit of each motor to detect the completion of disconnection of the faulty motor from the line. Short-circuit protection method for multiple electric motors. 5. A short-circuit protection method for multiple electric motors by impark drive, in which the completion of disconnection of the failed electric motor from the line is detected in conjunction with the operation of the overcurrent protection device, in the method according to claim 1. 6. In the method described in claim 1, the inverter is synchronized with the rotor position of the motor to distribute the ignition signal such as a gate pulse, and the ignition signal is distributed on the power supply side of the ignition signal distributor. A short-circuit protection method for multiple electric motors driven by an inverter, in which the inverter is stopped and restarted by turning it on and off. 7. In the method described in claim 1, the impark is synchronized with the rotor position of the motor and a ignition signal such as a gate pulse is distributed, and the ignition signal is distributed on the power supply side of the ignition signal distributor. When restarting,
A short-circuit protection method for multiple electric motors using an inverter drive, which stops and restarts the impark by adjusting the DC power supply voltage to the impark according to the rotational speed of other electric motors. 8. In the method described in claim 1, the inverter is synchronized with the rotor position of the electric motor to distribute the ignition signal such as a gate pulse, and the ignition signal is distributed on the power supply side of the ignition signal distributor. In addition to shutting off and turning on, when restarting,
A short-circuit protection method for multiple electric motors driven by an inverter, in which the inverter is stopped and restarted by adjusting the impark current lead angle according to the rotational speed of other electric motors. i In the method set forth in claim 1, the inverter is of a type that distributes an ignition signal such as a gate pulse using an oscillator or the like that is unrelated to the rotational speed and rotational position of the motor, and A short-circuit protection method for multiple electric motors driven by an inverter in which the impark frequency is matched and the inverter is restarted.