Analysis of the working principle of soft starter

Soft start technology is an emerging technology for controlling and starting motors. Nowadays, it has received widespread attention from modern people and has been actively applied in corporate production activities. This technology can start the motor smoothly, reduce the voltage well, and compensate and convert the motor, thereby effectively reducing the adverse effects of motor starting on the power grid and related equipment, thereby effectively protecting various related equipment.

Working principle of soft starter: When the motor reaches the rated speed, the starting process ends, and the soft starter automatically replaces the thyristor that has completed the task with the bypass contactor to provide rated voltage for the normal operation of the motor, so as to reduce the heat loss of the thyristor, extend the service life of the soft starter, improve its working efficiency, and avoid harmonic pollution in the power grid.

A soft starter is a device used to start a motor. It controls the voltage and current changes during the motor starting process to achieve smooth acceleration of the motor during the starting process, avoid shock and damage during the motor starting process, and also reduce the power factor and noise during starting. The working principle of a soft starter can be divided into the following steps:

1. Starting stage: When the motor starts, the voltage will not be output directly to the motor at once. Instead, a sine wave compensation circuit is used to compensate the voltage, reduce the peak value of the voltage, and limit the instantaneous jump of the current, so that there will be no instantaneous impact when the motor starts.

2. Intermediate stage: During the starting process of the motor, the output voltage and current gradually increase. In this stage, the soft starter will gradually increase the output voltage and current according to the set acceleration curve to make the motor accelerate smoothly and avoid problems caused by excessive current during the starting process.

3. Acceleration phase: When the motor reaches the running state, the soft starter controller turns on the bridge circuit breaker and outputs the power supply voltage directly to the motor, and the motor will run at normal power.

In short, a soft starter is a control device added before the motor starts. By controlling the voltage and current changes during the starting process, it can achieve smooth acceleration of the motor, protect the motor, reduce power factor and noise, and improve the reliability and safety of the equipment.

ABB soft starter (soft starter) is a novel motor control device that integrates motor soft start, soft stop, light load energy saving and multiple protection functions. It is called Soft Starter abroad. The soft starter uses three-phase anti-parallel thyristor as a voltage regulator and connects it between the power supply and the motor stator. This circuit is like a three-phase fully controlled bridge rectifier circuit.

When the motor is started with the ABB soft starter, the output voltage of the thyristor gradually increases, and the motor gradually accelerates until the thyristor is fully turned on. The motor works at the mechanical characteristics of the rated voltage, achieving smooth starting, reducing the starting current, and avoiding starting overcurrent tripping. When the motor reaches the rated speed, the starting process ends, and the soft starter automatically replaces the thyristor that has completed the task with the bypass contactor to provide the rated voltage for the normal operation of the motor, thereby reducing the heat loss of the thyristor, extending the service life of the soft starter, improving its working efficiency, and preventing harmonic pollution from the power grid.

The soft starter also provides a soft stop function. The soft stop process is opposite to the soft start process. The voltage gradually decreases and the number of revolutions gradually drops to zero, avoiding the torque shock caused by free stop.