Industrial motors have a broad scope of applications and work on high-voltage supply. Starting the motor is as important a part of the operation as its running. An uncontrolled start has severe consequences on the sensitive electrical and electronics equipment, power consumption and the lifespan of the motor itself. To control this start, a soft starter is used with the motor. It controls the voltage disturbance, safeguarding the motor from behaving abnormally. This blog discuss the function and applications of soft starter, and how to choose the best among the soft starter manufacturers.
Need for Soft Starter
When the induction motor, especially in the high voltage circuits, have no control at the start, it draws current in much higher capacity. This reduces the voltage being transmitted to the connected instruments. The voltage sag can malfunction the instruments like HVAC, PLC sensor, computer, etc. It can damage the gears, conveyor belts in industries, vessels and pipes in the plumbing and drainage systems, and many more problems on large scale. Soft starter manufacturers resolve this issue by making a device that gradually increases the voltage to control the current flow in the motor.
Components and Working
A soft starter is an assembly of Silicon Controlled Rectifiers (SCRs) as fast-acting switches, control circuit, bypass contactor, and human-machine interface. When it receives signal to start, it provides a reduced voltage to the motor. This reduce the high inrush current and torque. Voltage increase is gradual till the motor reaches peak speed. At full motor speed, the bypass contactor stops the rectifier so that heat is not generated excessively. Similar to starting, the SCRs can also gradually reduce voltage to stop the motor smoothly instead of sudden halting.
How To Select the Right Soft Starter
These are the key factors you need to discuss with soft starter manufacturers:
Current and Voltage Ratings
This is non-negotiable part of any electrical equipment you will buy. In case of soft starter, match with the current and voltage ratings of the motor that will be connected. To handle the inrush currents effectively, the rated current of the soft starter should be higher than the motor at full load.
Type of Application
The type fo application varies from load and frequency of start. For heavy load like crushing and grinding, the soft start is expected to control high torque. For pumps and fans, it needs to have stop feature along with starting. So discuss the type of application with the soft starter manufacturers.
Bypass Feature
As the motors reaches full speed, the SCRs in soft starter generate heat and continue to consume power if it doesn’t have a bypass switch. Having a bypass contactor lets current pass through the rectifier and saves power loss and also extends the lifespan of the soft starter.
Conclusion
The heavy loaded motors in the industrial and commercial applications require controlled starting and stopping, and a soft starter is a reliable solution for this purpose. It is better than star-delta strarter because they have limited scope, and variable speed drives because they are complex. Consult the application type, compatibility with ratings of your motor and additional features when discussing with the soft starter manufacturers.
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