Air compressor motor burned Case Analysis - Contactor issue

The contactor is one of the most important components in the motor control circuit, it can destroy the best selection of unreasonable compressor. Press contacts load the correct choice is extremely important.

Contactor must be able to meet the harsh conditions, such as rapid cycling, sustained overload and low voltage. They must have heat, select the contact material is large enough surface area to distribute the load current to be generated at startup or stall other large currents to prevent welding.

For safety and reliability, while the compressor contactor to disconnect the three-phase circuits. Contactor rated current can not be lower than the rated current of the compressor nameplate. Specifications small or poor quality of the contact can not withstand the compressor starts, stall and high current at low voltage shocks, prone to single-phase or multiphase contact bounce, welding or shedding phenomenon, caused by damage to the motor.

Contact bounce contactors frequently start and stop the motor. Frequent motor starts, a huge starting current and heat, will exacerbate the aging of the winding insulation. Each time you start, the magnetic moment of the motor windings and friction between the tiny moving. If there are other factors complex (such as metal shavings, poor insulation oil, etc.), it is likely to cause a short circuit between the windings. Thermal protection system is not designed to prevent such destruction. In addition, the jitter of the contactor coil likely to fail. If there is contact with the coil is damaged, prone to single-phase state.

If the contactor selection is small, the contact arcing and can not afford to stop due to frequent open loop or unstable temperature control circuit voltage generated by welding or may be detached from the contact holder. Welding contact will cause permanent single-phase state, the overload cycle continuously turned on and off.

Needs to be stressed that the contactor contacts welded together, the dependence of the compressor power contactor disconnect all control loop (such as high and low pressure control, hydraulic control, defrost control, etc.) will all fail, the compressor is unprotected state.

Thus, when the motor burned, check the contactor is essential step. A contactor is an important cause motor damage is an often forgotten.