Research On Breaking Control Strategy Of AC Contactors Based On Arc Erosion

As a device used to make and break the circuit,AC contactor is required to operate frequently and have a long electrical life.The failures of AC contactors are mainly caused by the arc erosions during breaking electrical circuits,and therefore,the electrical life of contactors can be increased by contro lling the arc erosions properly.The CJX2-18 AC contactor is chosen to be researched in this paper.And a series of work is carried out on the arc duration,the arc erosion and the electrical life.Firstly,the effect of arc starting phase angle(ASPA)on the arc duration and the arc erosion of both the single contact and the three-phase AC contactor was analyzed.The three-phase AC contactor can be used under two load models.When the load neutral is connected to the power neutral,it is called N TN load model,and when the load neutral is not connected to the power neutral,it is called NNC load model.The arc erosion of the two load models was analyzed separately.Then,the differences of the electrical life under three control modes,including the random ASPA control,the fixed ASPA control and the three-phase uniform wear control,were investigated in detail.Also,the electrical life under two load models was compared.Secondly,the randomness of the ASPA caused by the inconstant release time of AC contactor was introduced and the characteristic of contactor’s electrical life under this randomness was analyzed through simulation.A control method based on the standard deviation of ASPA to control the optimal releasing moment of AC contactor,in terms of minimizing the arc erosion,was proposed in this part.Finally,the complex variation of the ASPA with the increase of operations was considered.The control method was improved so that the releasing moment of contactor can be adjusted properly and automatically according to the real-time operating parameters to maximize the electrical life of AC contactor.Experiments under the three control modes prove that the arc erosions of three contacts are almost the same and the erosion rate is the minimum under the maximum life control,and the electric life of the AC contactor is significantly increased.