Several common parameters of motor soft starter:

(1) Start ramp

The start ramp is the time from the soft starter start ramp (initial voltage) to full voltage. The ramp time should not be too long, as this will only lead to the risk of unnecessary heating of the motor and tripping of the overload relay.

If the motor is unloaded, the starting time of the motor may be shorter than the set ramp time. If the motor is heavily loaded, the starting time may become longer.

(2) Shutdown ramp

When a soft stop motor is required, such as a pump or conveyor belt, use the stop ramp. The shutdown ramp is the time from full voltage to reaching the stop voltage (initial voltage).

(3) Initial voltage

This is the starting point for the soft starter to start or stop the ramp, as shown in the figure above. The torque of the motor will decrease with the square of the voltage. If the voltage is set too low, such as 20%, the starting torque will only change to 0.2 * 0.2 = 0.04 = 4%, and the motor will not start from the beginning.

(4) Current limiting

The current limit can be used in applications where limited starting current is required, or in heavy-duty starting where it is difficult to achieve perfect starting only by setting the initial voltage and starting slope.

When the current limit is reached, the soft starter will temporarily stop increasing the voltage until the current drops below the set limit, and then continue to rise to full voltage.

(5) Step down voltage

The step-down voltage provides a special type of stop ramp. The voltage can be adjusted so that it drops to the level at which the motor starts to drop immediately after the stop command is issued.

For low load motors, the speed will not decrease until very low voltage is reached, but this phenomenon can be eliminated by using the step-down function, especially when the pump is stopped!

(6) Adjustable rated motor

Adjustable rated motor current the motor rated current can be set on the soft starter of the motor used. This setting may also affect other values, such as the trip level of the electronic overload relay, the level of the current limiting function, etc.