The "trip" fault is usually caused by the external power supply, which is not the cause of the air compressor itself and does not need to be handled; The "trip" fault caused by the tripping of other overload protectors must be taken seriously. If forced operation occurs, the air compressor unit may be scrapped.

There are many reasons for tripping, the most common is high temperature tripping, especially in the summer when the temperature is high.

The following are some other unusual reasons. These unusual reasons are usually difficult to maintain, and unfamiliar after-sales maintenance personnel will feel "troublesome" when encountering these problems. Through this article, some ideas are provided to help maintainers master several reasons for air compressor tripping.

1. Start under pressure

The so-called starting of the air compressor under pressure refers to the tripping caused by the high back pressure of the compressor when the air compressor is started. For example, if the mechanical pressure gauge on the compressor oil and gas tank is checked on site, if the pressure gauge shows that there is pressure, it is preliminarily judged that the system may not be fully depressurized, causing the compressor to start under pressure. At this time, because the starting current is too high, the air switch trips to protect the unit.

2. Excessive head resistance

Excessive head resistance will lead to excessive compressor starting current, that is, the compressor is overloaded, causing the air switch to trip. There are three main situations that can lead to increased head resistance:

① The viscosity of lubricating oil is high. The temperature in the south varies greatly with seasons. The ambient temperature in summer can reach about 40 ℃. The viscosity of the lowest lubricating oil in winter is inversely proportional to the temperature. The viscosity of lubricating oil in winter is significantly higher than that in summer;

② For single screw compressor, the screw and star wheel in the head are easy to coke. The work of the single screw compressor mainly completes the air compression process through the engagement of the screw and the star wheel. The working efficiency of the compressor is determined by the clearance between the screw and the star wheel;

③ There is too much lubricating oil in the machine head. The oil cut-off valve at the outlet of the machine head fails. If the oil cut-off valve is not closed in time after the compressor shuts down, a large amount of lubricating oil will be pressed into the machine head again, resulting in excessive starting resistance during the starting process, increasing the starting torque of the motor, increasing the starting current, and causing the overload protection to trip.

3. Electrical device failure

Many users use 380V motors, which are started in the step-down starting mode of star delta conversion, earlier in the star mode. When the startup starts, turn to triangle operation mode 2~3s later. If the star delta change-over switch fails, normal star delta change-over cannot be carried out. The star current is many times higher than the triangle operating current, generally about 5~7 times. When the protector is delayed, the compressor will jump naturally. In addition, due to vibration and other reasons, the shortening of the starting time set by the air switch may also lead to the instantaneous jump of starting.

The most direct and effective way to judge whether it is an electrical fault or a mechanical fault is to separate the motor from the head, that is, remove the coupling or belt at the head end, and manually turn the compressor host and motor respectively to eliminate mechanical problems.

4. Unloading valve failure

Unloading valve is an important part of screw compressor, its main function is to control the loading and unloading of the unit, that is, to control the air intake of the compressor.

Opening the unloading valve in advance is a fault that is not easy to find. Before starting the compressor, the unloading valve is closed. During the starting process, the unloading valve is slowly opened or fully opened after the start. If the unloading valve is opened too early, it means that the starting load of the compressor is too large, which leads to the increase of the starting current of the air compressor, causing the compressor to jump.

5.  High temperature of motor

(1) When the instantaneous voltage of the motor exceeds 10% of the rated voltage in summer, or the instantaneous voltage of the motor is lower than the rated voltage by more than 5%, it will cause the motor to heat up and temperature rise under the rated load. In this case, the voltage should be checked and adjusted;

(2) The motor starts too frequently, the operating environment temperature is too high, and the ventilation is not smooth. Reduce startup times

Reducing ambient temperature, ensuring smooth air duct, eliminating dust and oil contamination, and keeping the fan running well can help solve similar overheating problems;

(3) The unbalanced three-phase power supply voltage of the motor will also cause the motor to heat up. This is because when the unbalanced three-phase power supply voltage exceeds 5%, the unbalanced three-phase current will be caused. The solution is to check and adjust the voltage;

(4) The contact problem of the power switch of the motor and the open circuit of one phase fuse will cause open phase operation, which will lead to the temperature rise of the motor. The solution is to repair or replace the damaged parts.