1: When the switch valve is running in the direction of the motor, the contactor is burned:
When the automatic control valve was switched from open to closed, there was a burning contactor (A-KA65, A-KA66), which was almost a pair of damage. If it is a manual on-site on / off valve, there is no problem, indicating that there is no problem with the wiring, and the circuit already has interlocked electrical logic. Check again, there are no problems with the hardware. When the contactor was damaged again, it was removed and inspected. It was found that the main contact was burned, indicating that the current was very large, and there was no time for the thermal relay to jump. And this happens only when the valve is in automatic control mode.
Analysis: Paired contactors are burned. It is impossible to see from the circuit. There is only one possibility. The contactor is caused by arcing: when the contactor that opens the valve has not been released, the contactor that is closed is closed. If the lower action is issued quickly, it will cause an instant short circuit and damage the contactor.
ways to improve:
1. If allowed, the time interval for issuing the command to open the on / off valve.
2. Improve the hardware circuit. A normally open / normally closed contact of a relay is used as the reversing control switch of the valve electric device .
Two: Phase-loss burning motor of valve power supply:
High-power valve 380VAC power supply, powered by contactor, with thermal relay protection. When the valve is opened, the valve does not move. The circuit check connection was correct, the valve still did not move, and finally opened the valve and found it was burned, but the heat relay did not jump. Carefully inspect the line again and find that one end of the contactor main line is not tightened.
Analysis: Because one phase of the three phases of the power supply is not firmly connected, the phase is missing. In this case, the motor is easily damaged, and the heat is too late to react.
Note: When connecting the motor circuit of the three-phase power supply, the three phases must be connected firmly.
3: The valve has a long installation distance and the return signal interferes:
After the valve is opened or closed, the valve in-position signal is incorrect. The on-site valve detection signal has been sent out, but the control system cannot receive the signal.
Analysis: When the valve position is a certain distance from the control cabinet, the wrong information will be returned due to the attenuation of the signal.
Improvement method: 1. Increase the diameter of the signal transmission cable and choose a shielded cable.
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