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Soft Starters: A Closer Look at the Main Categories

Today, our industrial facilities use a wide range of machinery and their safety, as well as that of the operators, is very important. Soft starters are small motors designed to start with less power supplied to them at startup. This is crucial in helping to reduce electrical and mechanical shocks on the system.

Soft starters are also used in stopping, reversing, and protecting your industrial equipment. So, whether you have a DC or AC electric motor in your facility, the chances are that it has or requires a soft starter motor. So, how well do you know soft starters? Keep reading as we dig deeper to highlight the main categories and applications.

Why are Soft Starters So Important?

Soft starters are used to place a device known as a reduced voltage starter between the incoming utility line and the main motor. Therefore, they help to regulate the current that is getting into the motor. Therefore, they allow the AC induction motors to run at a slower pace, implying that the torque also remains low. Here are the main reasons for using soft starters:

  • Avoiding unnecessary wear and tear of your equipment.
  • Reducing the risk of overloading the power distribution system.
  • Reducing the risk of overheating.
  • Reducing cost of maintenance for motors, pumps, lathe machines, and conveyor systems, among other facilities.
  • Improving the efficiency of your machine.

Let’s take an example here. If you take a standard NEMA design B motor, it can draw up to six times the full operating current at startup. This could mean that your system is likely to suffer from problems like blowing off the fuses or flickering lights. For facilities that deal with hazardous materials, this might be all that is required to cause a spark that will raze the entire facility down. To avoid this, you need a soft starter. Make sure to also use lighting fixtures for hazardous areas.

Common Types of Soft Starters

Soft starters can be grouped into a number of categories. The main ones include the primary resistor, auto transformer, and part winding.

Primary Transistor

This type of soft starter was designed in the 1990s and was one of the first models to be used in industrial operations. The starters are designed with resistors that help to reduce current flow. Most primary resistor categories offer two-point acceleration or have only one step of resistance. You might want to add more stages of contactors and resistors for a smoother starting.

Auto Transformer

Auto transformers are the most preferred option when it comes to soft starting motors. Instead of using resistors, like the primary transistor soft motors, the auto transformer is designed to use taps fitted on transformer windings for power control. Most taps are rated 50%, 65%, and 80% of the main voltage.

The taps come with greater flexibility, activating one of the three taps so that different current levels can flow to the motor. The starter can help supply higher current levels, depending on the tap selected, to the motor, while maintaining current at low levels.

Part Winding

This soft starter works by dividing the windings in a motor into separate identical sets. At startup, the power is only allowed via one set of windings, and the other sets are only released when the motor gains speed. The main advantage of the Part Winding soft starter is that you are able to keep the current low and starting torque minimum.

As you can see, soft starters are crucial if you have equipment that uses motors. Remember to always ensure you buy the right models by checking your equipment's electrical power range, enclosure type, and design. More importantly, always bit from top-rated brands.