How to judge the wearing degree of the electrical contacts
Posted by Vitalina Sokol on
To determine the degree of electrical wear of the contacts
Whether from a functional or an economic point of view, it is necessary to determine the degree of wear of the contacts. Maintaining the contactor too early will increase the total cost, and it is more economical to maintain the contactor at the appropriate time to avoid equipment interruption or accident.
Longitudinal
Different application categories, different load contact wear rates are different. For motor control, it is also related to the starting method of the motor. Some of the commonly used application categories are listed below.
AC-1. (General purpose)
Non-inductive or low-inductive loads, resistance furnaces. Since the starting current is equal to the rated current, the pull-in of the main contacts is relatively easy. Breaking at full pressure, the energy of the arc is rather low.
AC-2. the slip ring motor starts and stops
The typical on and off current is about 2.5 times the rated current of the motor, and the breaking voltage corresponds to the full voltage.
AC-3. Squirrel cage motor starts and stops.
Depending on the characteristics of the motor and the type of load, the current when the contacts are closed is about 6 to 8 times the rated current of the motor.
Breaking is relatively easy, because at this time the current is equal to the rated current of the motor, and the voltage drops to 17% of the rated voltage. Typical contact wear is from contact closing operations. Check the contactor under AC-3 application, generally no or very few contact material particles can be seen in the arc chute.
Initial stage of life of dynamic and static contacts in AC-3 application
The mid-life stage of dynamic and static contacts in AC-3 applications
End-of-life stages of dynamic and static contacts in AC-3 applications
