Zhigang Li

Test and analysis of reliability for electromagnetic relay

As relays are widely used in automatic control systems and communication systems, the reliability of relays is very important. Electromagnetic relays, type 155, were tested for their reliability in this paper. The test load was DC 24 V/spl times/0.1 A. During the test, the contact voltage drop, closing time and opening time were monitored and measured. At the end of test, we estimated the reliability of the relay according to the test results and analyzed the failure mode. The failure mechanisms were analyzed by observing the surfaces of failing contacts. We proposed a method for reducing the relay failure rate.

Study and reliability analysis on testing instrument for dynamic contact resistance on contact

In this paper, a new testing instrument for dynamic contact resistance of low capacity contacts is introduced in detail. By means of this testing instrument, we carried out a series of experiments. In early experiments, we tested several types of industrial control relays under different temperatures and operation times, and accumulated a great deal of experimental data. By statistical analysis of the test data, we drew some qualitative conclusions. Further experiments and reliability analyses are ongoing. A mathematical model of the contact resistance of electrical apparatus contacts and its dynamic changing principle are preliminarily discussed.

Reliability analysis and failure prediction study of dynamic contact resistance on contact

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.

Concerning contact resistance prediction based on time sequence and distribution character

We take statistics on experimental data, including static contact resistance, bounce time and the max contact resistance of relays matching contacts in the dynamic closing process. A conclusion is drawn that the contact resistance is not in obedience to the normal distribution function. The further analysis makes clear that the contact reliability on contacts has correlation with the eigenvalues of diagnostic parameters and the figure of their distribution density curves. The reason for these is discussed preliminarily. On the ground of the above work, we develop the contact resistance prediction model based on time sequence and distribution character.

The research on electrical life test condition of relay with electromotor load

This paper presents research on the condition of voltage and current when the relay, loaded with an AC single-phase asynchronous motor (SPAYM), turns on and off. According to the arc model and equivalent model of SPAYM during its operation, the dynamic changing process of voltage across the contacts and loop current (when the relay turns on and off) are theoretically analysed and simulated by means of a computer. Furthermore, the conclusions are compared with the actual measured results. The electrical life test condition of relay is consequently obtained from this. Finally, a computer control test device is presented.