Soft Starts – Your Questions Answered

What is a soft start?
A soft start is a small device which is fitted to protect your electric motor from damage caused by sudden influxes of power.

When should I use a soft start?
If you are running a motor of 15Kw or above, a Direct-on-Line (DOL) start may overload the local supply network, causing voltage variations which could interfere with other electrical plant and affect how your processes function. There is also the ongoing wear and tear caused by torque shock or high voltage levels at start up.

A soft start acts as a reduced voltage starter, overcoming issues caused by DOL and torque shock and protecting your equipment from costly breakdowns and downtime.



I’ve heard Variable Speed Drives do the same thing as Soft Starts, what is the difference?
A Soft Start and a VSD have a commonality in that they both provide a controlled start and stop for motors starters, starting motors up gradually for improved performance. However, a Soft Start is only suitable for constant speed applications, whereas a VSD can vary the frequency of the supply to a motor according to need.

How do I know what’s best for my application?
A Soft Start provides a much cheaper option to installing a VSD. If you are running a motor with a constant speed, then a soft start is the answer. There is no real financial benefit to installing a VSD when there is no room to vary the speed, as the energy saving potential of a VSD will be wasted

For advice on the best course of action for your application,
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