rotation of the compressor

Figure 1: A piston compressor is rotating.

As we know, the operation of the internal compression structure of the refrigeration compressor has a fixed direction. First of all, we should make it clear that the reverse rotation of the compressor is adverse.

Scroll refrigeration compressors can only compress in one direction of rotation. Single-phase compressors always start and run in the correct direction, except in the case of instantaneous power failure. The direction of rotation of the three-phase compressor is determined by the phase sequence of the power supply, so there is a chance that the compressor will rotate reversely.

When installed in the field, the refrigeration compressor can be determined to be rotating in the correct direction by the decrease of the suction pressure and the increase of the exhaust pressure. In addition, if the compressor is in reverse rotation, the noise of the compressor is abnormal, and the running current is obviously lower than normal.

However, long periods of reverse rotation damage refrigeration compressors, and equipment manufacturers can set up phase sequence protection modules in the control loop to ensure that the compressor does not run in the case of the wrong phase sequence. Generally speaking, the scroll compressor only needs to be replaced with any phase of the three-phase line.

There is a situation that will lead to the reverse rotation of the refrigeration compressor, which is the instantaneous power failure. It means that the power failure time is less than 0.5 seconds, which may cause the rotation direction of the single-phase compressor to change.

The compressor will continue to rotate in a reverse direction for several minutes after being powered, until the compressor motor protector operates. This has no effect on the compressor, which restarts and runs in the correct direction after the motor protector is reset.

We recommend that you use a relay that can sense instantaneous power outages, so that the device can lock the compressor for two minutes before allowing it to restart.

Reverse Rotation of Car AC Compressor

The compressor of the car is in the air conditioner unit that is essential. Most of the moving parts of the automobile air conditioning system are on the compressor, so the compressor requires much maintenance. The common faults of the general compressor are plugging, leakage, refrigeration failure and abnormal noise.

Most compressor faults can be troubleshot, but because the number of compressor parts are small, and it requires high assembly accuracy requirements, special tools and fixtures are needed. Next, we will explain to you the solution to the reverse rotation of the compressor after the car is stopped.

Car AC Compressor

What is the cause of reverse rotation of the automobile air conditioner compressor? Check valves and exhaust valves are not closed strictly, causing compressed air to flow back into the cylinder to push the piston, so that the air compressor rotates reversely.

However, because the compressor has a transmission relationship with the engine, such as belt transmission, and the intake valve is closed, it is actually very difficult to be reversed. Compressed air can leak through the compressor.

In general, the rotation direction of the compressor is the same as that of the engine, except for some special, limited by installation conditions. At present, only the scroll compressor rotates in direction, once there is the opposite direction of rotation, it will burn the compressor.

Introduction to Compressor

compressor rotor failure

Figure 2: Rotors of the compressor are stuck.

Changing the positive and negative terminals of the power supply will lead to the reverse rotation of the compressor.

The compressor is a driven fluid machine that lifts low pressure gas to high pressure gas. It is the heart of a refrigeration system. It inhales the gaseous refrigerant with low temperature and low pressure from the suction pipe, compresses it by the motor operation, and then emits the refrigerant with high temperature and high pressure to the exhaust pipe to provide power for the refrigeration cycle.

It thus realizes the cooling cycle: compression → condensation (exothermic) → expansion → evaporation (endothermic).

The linear compressor uses the magnetic levitation principle and spiral circulation physical structure to compress gas and provide power for refrigeration.

The compressor is dived into the piston compressor, screw compressor, centrifugal compressor, linear compressor and others. A piston compressor is generally composed of the shell, motor, cylinder, piston, control equipment (starter and thermal protector) and cooling system.

There are three cooling methods, including oil cooling, air cooling and natural cooling. Linear compressors have no shaft, cylinder, seal and heat dissipation structure. The compressor of a household refrigerator and air conditioner take a single-phase alternating current as of the power supply. Their structure principle is basically the same, but their refrigerant is different.


After a refrigeration compressor is shut down, you should make sure it does not rotate reversely. When the compressor rotor is static, there is still a large capacity of process gas in the pipeline, as well as a certain pressure.

At this time, the compressor rotor stops rotating, and the pressure in the compressor is lower than the pressure in the pipeline. And if the compressor outlet pipe is not installed on the check valve or check valve is far away from the compressor outlet, the gas in the pipeline will flow backward, making the compressor rotate reversely, and also drive the turbine or motor and gear transmission rotor reverse.

The normal lubrication of the bearing is damaged by the reverse transfer of the rotor of the compressor unit, which changes the force condition of the thrust bearing, and even causes the loss of the thrust bearing. The dry gas seal will also be damaged due to the reverse rotation of the compressor.

In order to avoid this fault, the following three problems should be noted.

The compressor outlet pipe must be set up on the check valve, and installed near the outlet flange, so that the distance between the check valve and the compressor outlet is reduced as far as possible. Therefore, it minimizes the gas capacity in this section of the pipe without causing inversion.

According to the situation of each unit, you should install the vent valve, exhaust valve or recirculation pipeline. When the compressor is shut down, you should open these valves in time to remove the high-pressure gas from the compressor outlet to reduce the gas capacity stored in the pipeline.

When the compressor is shut down, the gas in the system may be poured back into the compressor. The high-pressure and high-temperature gas is poured back into the compressor, which can not only cause the reverse rotation of the compressor, but also burn out the bearing and seal. If the gas flows backward, it has caused more accidents. So you must pay attention to it.

5h15 car ac compressor

Figure 3: A car ac compressor.

In order to effectively prevent the occurrence of the above accidents, the following two things must be done before speed reduction and shutdown.

Open the vent valve or backflow valve, so that the gas vent or backflow.

Close the check valve of the system pipeline.

After that, slow down the compressor gradually and stop the machine.

The abnormal sound of the car compressor can also be solved. The possible causes include liquid shock caused by many kinds of wrong filling, blockage of air conditioning system, excessive system load caused by the excessive filling of snow, which causes damage or death of compressor internal parts.

In this case, you should replace the compressor or parts. In addition, the worn compressor clutch bearing, excessive clearance or lack of oil causes abnormal sound, then you should remove the belt, rotate the compressor belt pulley by hand, listen to it.

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