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Compressor as the heart of the refrigeration system, its stable operation is very important to the performance of the whole system. However, in practical applications, compressor motors may burn out for a variety of reasons. When the motor burns out, in addition to directly replacing the damaged components, it is necessary to deeply analyze the root cause of the failure to avoid similar problems.
Ac contactor
Ac contactor is one of the important parts in the motor control loop, and improper selection can destroy the best compressor. It is extremely important to select the contactor correctly according to the load. Ac contactors must be able to meet demanding conditions such as fast cycling, sustained overload and low voltage. They must have a large enough area to dissipate the heat generated by the load current, and the contact material must be selected to prevent welding under high currents such as starting or blocking.
The contactor must meet the following requirements:
Minimum closing voltage: The contactor should be able to close normally at 80% of the nominal voltage of the nameplate, ensuring smooth operation even in the case of power grid fluctuations.
Rated current capacity: The rated current of a single contactor should exceed the rating value (RLA) on the motor nameplate, and should be able to withstand the high current generated when the motor is blocked. If two contactors are used, the separate winding of each contactor should not be less than the half winding of the compressor.
Heat dissipation performance: Contactors should be designed with sufficient surface area to dissipate the heat generated by the load current to prevent damage caused by overheating.
Contact material: Choose a contact material that can resist the welding phenomenon under high current conditions, especially in good condition at the moment of start or under the impact of large current when the motor is stuck.
Other things to note:
1, the rated current of the contactor can not be lower than the rated current on the compressor nameplate. Contactors with small specifications or poor quality cannot withstand the large current impact when the compressor starts, stops and low voltage, and are prone to single-phase or multi-phase contact jitter, welding or even falling off, causing motor damage.
2, the contactor with contact shaking will frequently start and stop the motor. The motor starts frequently, and the huge starting current and heat will aggravate the aging of the winding insulation layer. Each time the motor is started, the magnetic torque causes the motor windings to move slightly and rub against each other. If other factors cooperate, it is easy to cause short circuit between windings. In addition, the jitter contactor coil is prone to failure. If the contact coil is damaged, it is easy to appear single-phase state.
When the motor is burned out, the contactor must be checked. After the AC contactor contact adhesion, regardless of whether the motherboard has output, the compressor will work, and the "streaking" without protection for a long time, the compressor damage is an inevitable. When replacing the compressor, be sure to find the cause of compressor damage, be sure to check whether the AC contactor is normal, there is no lack of phase and adhesion. Can not only replace the compressor, without investigating the reasons, is bound to lead to the new replacement of the compressor secondary damage.
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