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With operating numbers of AC contactors, some tiny variations in mechanical performance and structural parameters would result in electrical performance change, and would extremely influence contactor's dynamic response in the end. So it is important to research on dynamic response and failure analysis of AC contactors. This paper introduces a general method to judge chaos motion and to forecast failure , which is based on Lyapunov Exponent (LE) to analyze AC contactors's dynamic response. It puts forward some academic theories in optimized-design and safe-operation of AC contactors.

Any contactor bounce is undesirable since this causes arcing which shortens the life of the contacts when contacts close. The rebounds and the closing speeds are different with the closing phase angle of the electromagnetic coil voltage switching on when contactors close. This paper discussed the determination of the best closing phase angle of the electromagnetic coil voltage switching on. Taking closing phase angle as optimization variable, the closing velocities of three phase contacts and armature as objectives, and taking moving velocities lower than their worst values as restrictions, the optimization model was established. Game theory was introduced and adopted to solve the multi-objectives optimization problem. Taking CJ20 AC contactor as an example, the best closing phase angle was determined by combing the calculating and testing results.

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-/spl pi/]. 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.

In previous research, a new testing instrument for dynamic contact resistance of a low capacity contact was developed, and, by means of this testing instrument, we carried out a series of experiments. In the experiments, we tested several types of industrial control relays under different environmental conditions, and accumulated experimental data. In this paper, our further research mainly focuses on the dynamic changing principle of dynamic contact resistances on the contact while contact time and operation times increase. Several characteristic values are distilled in the experimental data. We analyze these characteristic values using a statistical method of time sequences and draw some statistical conclusions. According to these conclusions, the reliability analysis and failure prediction method are further discussed.