The allowable current of the contact or contact of the voltage regulator of the diesel generator set shall not be damaged due to heating during normal operation, but more attention should be paid to prevent the contact surface from burning due to sparks when the contact or contact of the voltage regulator of the diesel generator set cuts off the circuit. Sometimes the automatic voltage regulator of diesel generator set can even melt the contact curve locally. The spark size when cutting off the current is not only related to the power supply voltage, but also to the load type.
Inductive load produces induced potential when power is off, which often exceeds the supply voltage. Therefore, the corresponding current values are often specified for different types of loads in the relay manual.
Note: the series or parallel connection of multiple contacts may not increase the breaking capacity by multiple times. This is because each contact on the same relay can not be turned on and off at the same time. The one that is later disconnected among the parallel contacts and the one that is first disconnected in series may be damaged.
In addition to using an intermediate relay or changing to a larger one, a spark elimination circuit can be used to eliminate smaller sparks (commonly used on AVR relays). Or use arc extinguishing device, arc extinguishing grid and other devices to eliminate large arc (commonly used on SE350 contactor).
For the AC circuit, because it is easy to extinguish the arc at the zero crossing moment, the allowable cut-off current value is larger than that of the DC circuit.
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