Modern soft starter

Modern soft starterOne of the main disadvantages of a squirrel-cage induction motor is that it has large inrush currents. If in theory the methods of reducing these shocks have been well developed for a long time, in practice these developments (the use of starting reactors and resistors, switching from star to delta, the use of thyristor voltage regulators ...) have been used in very rare cases cases.

Recently, however, everything has changed dramatically, as thanks to the progress of microprocessor technology and power electronics, convenient, compact and very efficient soft starters - electric motor soft starters - have appeared on the market.

A soft starter is a device that significantly increases the service life of an electric motor and actuators that work from the shaft of this motor. In the case of applying the supply voltage in the usual way, processes occur that destroy the electric motor. The voltage and starting current of the motor windings during transients are significantly higher than the permissible values.This causes wear of the insulation of the windings, «burning» of the contacts, a significant reduction in the service life of the bearings and the motor itself, as well as various devices that «sit» on the motor shaft.

Providing the necessary starting power requires an increase in the nominal power of the power supply networks, which leads to an increase in the cost of the equipment, as well as to the overspending of electrical energy. In addition, the «pulling» of the supply voltage when starting the electric motor can cause damage to the equipment used by these energy sources, this «reduction» causes irreparable damage to the equipment of the electric power supply, reduces its service life. At the time of starting, the engine is an important source of electromagnetic interference, which disrupts the operation of equipment powered by these electrical networks or located near the engine. When an emergency situation occurs — the motor is overheated or burned out due to heating — the parameters of the transformer steel change so much that the rated power of the rectified motor can decrease by more than 30%, due to which this electric motor will be completely unusable ex place. That is why the continuous power supply of the house and other important objects is impossible without a device for soft start of electric motors, which combines the functions of both soft start and soft stop, and protection of mechanisms and protection of electric motors.

A soft start with a soft starter is achieved by gradually increasing the voltage for slow and safe motor acceleration and reducing starting currents.In this case, the adjustable parameters are the starting voltage, the deceleration time and the acceleration time of the electric motor. A small starting voltage value can significantly reduce the starting torque of an electric motor, which is why it is often set in the range of 30 to 60 percent of the rated voltage value.

We advise you to read:

Why is electric current dangerous?