Soft-Start

Soft starter (soft starter) is a set of novel motor control device motor soft start, soft stop, light-load energy efficiency and various protection functions in one, foreign called Soft Starter. Soft start uses three opposite parallel thyristor as regulator, between the power source and the motor stator to access. Such a circuit such as a three-phase full-controlled bridge rectifier circuit. When using soft starter to start the motor, thyristor output voltage is gradually increased, the motor is gradually accelerated until the thyristor full conduction, working on the mechanical properties of the motor rated voltage to achieve a smooth start, reduce the starting current, avoid starting overcurrent trip. When the motor is to be rated number of revolutions, the end of the boot process, the soft starter has completed the task automatically replace thyristor with bypass contactor for the normal operation of the electric motor supplies the rated voltage to reduce heat loss thyristors, extend the life of the soft starter , improve their efficiency, but also to the power grid to avoid harmonic pollution. Soft starters also provide a soft stop function, soft start and soft stop opposite process, voltage decreases, the number of rotations gradually decreased to zero to avoid torque shock caused by free parking. Protection (1) Overload protection: Soft starter introduced a current control loop, so keep track of changes in condition detecting the motor current. By increasing the overload current setting and inverse control mode to achieve overload protection, motor overload, GTO and an alarm signal. (2) the lack of protection: at work, the soft starter detect a change in the three-phase line current at any time, once the drying occurs, you can make the lack of protection response. (3) thermal protection: The soft starter thermal relay inside the radiator temperature detection thyristor, once the heat sink temperature exceeds the allowable value of automatic turn-off thyristor, and an alarm signal. (4) Other functions: through a combination of electronic circuits can be realized in various other interlock protection system.