Causes and solutions for phase loss and abnormality of second-hand compressor power supply

A second-hand compressor is a driven fluid machine that upgrades low-pressure gas to high-pressure gas, and is the heart of the refrigeration system. It sucks in low-temperature and low-pressure refrigerant gas from the suction pipe, drives the piston to compress it through the operation of the motor, and discharges the high-temperature and high-pressure refrigerant gas to the exhaust pipe to provide power for the refrigeration cycle. In order to let everyone better understand this equipment, Aijiuku will briefly introduce the lack of phase, the abnormal reason and the treatment method of the second-hand compressor power supply. I hope it will be helpful to you.

Abnormal voltage and lack of phase can easily destroy any motor. The power supply voltage variation range cannot exceed ±10% of the rated voltage. The voltage unbalance between the three phases cannot exceed 5%. High-power motors must be powered independently to prevent low voltage when other high-power equipment on the same line starts and runs. The motor power cord must be able to carry the rated current of the motor.

If the compressor is running when a phase loss occurs, it will continue to run but there will be a large load current. The motor windings will overheat very quickly, and the compressor will be thermally protected under normal circumstances. When the motor windings are cooled to the set temperature, the contactor will be closed, but the compressor will not start, a locked rotor will appear, and a "locked rotor-thermal protection-locked rotor" endless cycle will be entered.

The difference in the windings of modern motors is very small, and the difference in phase currents when the three-phase power is balanced can be ignored. In an ideal state, the phase voltages are always the same, as long as a protector is connected to any phase to prevent damage caused by overcurrent.

The calculation method of the voltage unbalance percentage is the ratio of the maximum deviation between the phase voltage and the average value of the three-phase voltage to the average value of the three-phase voltage. For example, for a nominal 380V three-phase power supply, the voltage measured at the compressor terminal is 380V and 366V respectively. , 400V. The average value of the three-phase voltage is 382V, and the maximum deviation is 20V, so the voltage unbalance percentage is 5.2%.

In addition, in order to prevent the compressor from running out of phase, the compressors with three-phase power supply are equipped with phase sequence protectors. The phase sequence protectors have two functions. One is to prevent the wrong phase sequence from running the compressor in reverse; the other is to prevent compression. The machine is running out of phase.

The above content is a detailed introduction about the lack of phase of the power supply of the second-hand compressor, the reason for the abnormal power supply and the treatment method, I hope it will be helpful to everyone. If you want to know more about second-hand equipment, you might as well pay attention to jiuku.