Home > Exhibition > Content

Eliminate dc contactor, relay arc circuit

Jan 03, 2019

                                                          

Eliminate dc contactor, relay arc circuit

                                                      1


When the dc contactor and dc relay lose power in the coil, due to the sudden change of coil current, a high self-induced electromotive force will be generated, which is superimposed on the gap of the contact with the power supply voltage to form arc light discharge. Due to the existence of arc, on the one hand, it will burn out the contact, on the other hand, arc light discharge process, the circuit has current flow, damage to other components of the circuit. In order to eliminate the arc, the resistance and capacitance can be connected in parallel at both ends of the contact to extinguish the arc, as shown in the figure above.


When the contactor or relay coil is cut off, due to the existence of capacitance, on the one hand, the circuit reactance will be reduced, so that the self-induced electromotive force will be reduced; On the other hand, the voltage of contact gap forms a path of rapid discharge through resistance and capacitance, thus avoiding the generation of arc.


The capacitance should be chosen according to the principle that the load current per ampere is not less than 1μF. The resistance value should be chosen based on the principle that the capacitance discharge current is not greater than the allowable current value of the contact when the contact is closed.


In addition, diodes, resistors or capacitors in parallel at both ends of the coil can be used to eliminate the arc.