The direct start of the air compressor is to directly connect the power supply to the motor and start the motor to drive the compressor to rotate. It is usually used for small air compressors with power of 7.5kW and below. Features: Easy to operate, no additional controller or starting device required. · The instantaneous current is large, which is easy to produce power grid shock and overload protection action. · Usually used for screw air compressors with low power.

Star Triangle activated

The principle of star delta start (Y-Δ start) is: the star connection method is used first, and then converted to the Angle connection method when the speed is close to the rated speed, so as to reduce the starting current. Features: • Reduce the starting current and reduce the impact on the power grid. • The startup process is relatively complex, requiring pre-control of the circuit and a patient wait for a period of time at startup to keep the voltage and current stable. • Suitable for high power air compressor.

The principle of soft starting: the main motor is controlled by the soft starter, and the control circuit is triggered by the gate of the thyristor to limit the starting current of the motor. Features: • The starting current is 2-3 times the rated current, and the start is smooth. • Install a bypass contactor and switch to bypass after startup. • The soft starter needs to be checked and maintained regularly. • Suitable for high power air compressor. 

Frequency conversion start 

Frequency conversion start is to control the motor through the frequency converter to realize the smooth start and speed regulation of the motor. Features: • The motor starts smoothly, the starting current is small, and the impact on the power grid is small. • The speed and output power of the motor can be adjusted according to actual needs. • Suitable for large compressors. • Energy saving effect is obvious, which can reduce energy consumption and operating costs. • Relatively high cost. • Frequency converter, motor and control system should be checked regularly.