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How soft starters work

Time:2023-06-08   Visits:1094

The soft starter uses three-phase parallel thyristors as voltage regulators, which are connected between the power supply and the motor stator.

1: Working principle of soft starter

The soft starter uses three-phase parallel thyristors as voltage regulators, which are connected between the power supply and the motor stator. When using a soft starter to start the motor, the output voltage of the thyristor gradually increases, and the motor gradually accelerates until the thyristor is fully turned on, and the motor works on the mechanical characteristics of the rated voltage to achieve smooth start, reduce the starting current, and avoid starting overcurrent tripping.

When the motor reaches the rated speed, the starting process is over, and the soft starter automatically replaces the thyristor that has completed the task with a bypass contactor to provide the rated voltage for the normal operation of the motor, so as to reduce the heat loss of the thyristor and prolong the service life of the soft starter. Improve its work efficiency, and make the power grid avoid harmonic pollution. The soft starter also provides a soft stop function. The soft stop is the opposite of the soft start process. The voltage gradually decreases and the speed drops to zero to avoid torque impact caused by free stop.

2: What is a soft starter

The soft starter is a novel motor control device that integrates motor soft start, soft stop, and multiple protection functions. It is called Soft Starter abroad. Its main components are three-inverse parallel thyristors and their electronic control circuits connected in series between the power supply and the controlled motor.

Using different methods to control the conduction angle of the three-phase parallel thyristors, so that the input voltage of the controlled motor changes according to different requirements, different functions can be realized. Soft starters and frequency converters are two completely different products. The frequency converter is used in places where speed regulation is required, and its output not only changes the voltage but also changes the frequency at the same time;

The soft starter is actually a voltage regulator. When the motor is started, the output only changes the voltage and does not change the frequency. The frequency converter has all the functions of a soft starter, but its price is much more expensive than that of a soft starter, and its structure is much more complicated.

The motor soft starter uses a soft starter connected in series between the power supply and the controlled motor to control the conduction angle of its internal thyristor, so that the motor input voltage gradually rises from zero with a preset function until the end of the start, giving the motor Full voltage, that is, soft start. During the soft start process, the starting torque of the motor increases gradually, and the speed also increases gradually.

3: Three-phase motor soft start module

  What is a three-phase motor soft start module, it is a soft starter with miniaturization, small size, simple wiring, small power 1-22KW, and single-phase 1-8KW, without external bypass.

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