AC contactor making speed measuring and theoretical analysis

Three-phase alternating current contactors (abbreviated AC contactor) are electrical devices, which are applied to many fields in large quantities. It is important to improve their life and reliability. Reduction of contact bounce of AC contactor is the key problem to increase its life and reliability. The test of measuring the making speed of contacts and iron cores of AC contactor has been performed. The samples are CJ20-25 model of AC contactor, and the applied voltage for measuring is 380 V during the experiments. The full closing processes of AC contactor were measured at different closing phases of the coil voltage. The test results show that making speeds of the moving contact and iron core varies with the closing phase of the coil voltage. For the CJ20-25, there is a closing phase (about 75 degree) where the making speed of the iron core is the lowest in the range of [0-π]. In order to determine the best making phase to reduce the bounce speed of iron core as small as possible, the dynamic closing process of the AC contactor is analyzed theoretically by combining advantages of the two methods of "electromagnetic field" and "magnetic circuit", and the calculated results are in good agreement with the test results.