Compressor starting method
Several ways to start the compressor:
1) Direct start
2) Star corner start
3) Soft start mode
4) Frequency conversion start
5) Other
Start directly:
This starting method is mainly applied to low-power air compressors, the starting current is generally 7-8 times the rated current, and the moment of start-up is more harmful to the power grid.
Commonly used for relatively small compressors (refrigeration compressors, air compressors, etc.).
Usually consists of 1 contactor, 1 air switch, and 1 thermal relay.
Star corner start:
The starting current is 3-4 times the rated current, and the starting current is smaller than the direct starting current.
During the star angle switching process, there will be a peak current about 4-6 times the rated current. It is also quite harmful to the power grid and equipment.
At present, due to cost reasons, this method is widely used in compressor start and stop, but with the widespread use of soft starters and frequency converters. More and more applications are replaced by soft starters and frequency conversion (especially high-power compressors).
Soft start method:
Benefits of using soft start:
Reduce maintenance:
In the traditional star-angle starting method, during the motor starting process, the contactor pulls in and off will pass a large current, resulting in reduced contactor life;
The soft starter is used to control the main motor of the unit, and the control circuit of the SCR gate is triggered to control or limit the motor starting current;
Increase system reliability:
The traditional star-angle starting method can achieve overload, underload and phase sequence protection through the combination of components, which causes trouble in wiring and high failure rate. Poor system reliability;
The soft starter itself integrates a variety of protection, less wiring, and strong system reliability.
Frequency conversion start mode:
Covers all the advantages of the soft starter method. Compared with the soft start method, it has better advantages:
The starting current is smaller, below 1.5In, so the required grid capacity is also the smallest, and the most stable starting.
The compressor speed can be adjusted, and the compressor speed can be adjusted according to the actual load to achieve energy saving.
Compared with the soft starter, the protection is more abundant, the diagnosis is easier, and the man-machine interface is more friendly.
Achieve more communication methods to facilitate integration in different control systems.