1, according to voltage classification: high voltage soft starter, low voltage soft starter;
2, according to the classification of media: solid soft starter, liquid resistance soft starter;
3, according to the control principle: electronic soft starter, electromagnetic soft starter;
4, according to the operation mode: Online soft starter, bypass soft starter;
5, according to the load: standard soft starter, heavy-duty soft starter.
Starting mode
Based on the soft starter is connected between the power supply and controlled motor, control the turn-on angle of thyristor, the motor input voltage from zero to a preset function increased gradually, until the end of starting, the motor is given full voltage soft starter, soft starter in the process of the motor starting torque increases gradually, speed increased gradually. Soft start generally have the following several starting methods.
Ramp boost soft start: the starting mode is the simplest, does not have the current closed loop control, only adjust the thyristor conduction angle, so that it has a certain function relationship with time. The disadvantage is that, due to no current limiting, in the process of motor starting, sometimes a large impact current will make the thyristor damage, which has great impact on the power grid, but rarely used in practice.
Ramp constant current soft start: this starting method is in the initial stage of motor start, the current starts to increase gradually, when the current reaches the preset value to keep constant (T1 to T2 stage) until the start is finished. In the starting process, the rate of change of the current rise can be adjusted according to the motor load. When the current rise rate is large, the starting torque is large and the starting time is short. The starting mode is the most widely used starting mode, especially suitable for the starting of fan and pump load.
Step start: start, that is, in the shortest possible time, so that the starting current quickly reach the set point, that is, step start.
Soft starter (Figure 2)
Soft starter (Figure 2)
By adjusting the setting value of the starting current, the fast starting effect can be achieved.
Pulse shock starting: in the beginning of the starting stage, let the thyristor in a very short time, after a large current for a period of time to fall back, and then according to the original set of linear rise, connected to constant current start. The starting method is less used in general load, which is suitable for heavy load and needs to overcome the starting condition of larger static friction. The traditional decompression starting modes of cage motor include Y-q starting, self coupling decompression starting, reactor starting, etc.. These starting modes all belong to the start of stage decompression, and there are obvious disadvantages, that is, there are two shock currents in the starting process.
