Soft Starters? What do they do?

Electric motors typically require a large amount of energy when accelerating up to their top speed, that’s where Soft Starters come into play. Soft Starters are designed to help reduce the inrush currents and limit the torque experienced by an electric motor by switching the motor on and off at fixed speeds to achieve a lower start-up current.

Only used during the initialisation of an electric motor, the soft starter moderates the acceleration of the electric motor. This makes them ideal for helping to reduce motor heating and to protect and extend the life of the electric motor and its supporting systems.

Gently Does It

A soft starter should be used whenever there is a requirement for a reduced starting current to help achieve a smooth mechanical run-up.  Applications, where the use of Soft Starter is ideal, is within mechanical systems such as conveyor lines, gearing and belt-driven systems which might require a gentle start-up process to reduce tension, lash and torque spikes. Soft Starters are also found in pumped liquid systems where they help to eliminate troublesome pressure surges like water hammer that can occur within the pipework of pumped systems.

pump application soft starter

Soft starters can be used on most fixed speed applications and come second only to a Variable Speed Drive (VSD) in starting current applications. When an application calls for the switching of a motor at a fixed speed a VSD is the most efficient way of starting the motor in terms of heat and power losses but is consequently the most expensive option to take.

Cost-Effectiveness Solutions

Although a Soft Starter is more expensive on the initial outlay than a Direct On Line (DOL) and a Star Delta Motor Starter they are much more cost-effective than a Variable Speed Drive.  It is worth noting that despite the initial outlay, a Soft Starter will last far longer in operational terms than a DOL and a Star Delta Motor Starter by a factor of 10 times the capacity. Some models of Soft Starter contain condition and fault monitoring capabilities, adding additional benefits to an automation and process control installation by providing vital diagnostic messages and data that can aid in improving the process and maintenance of the set-up.

motor soft starter application

When looking for a Soft Starting solution you cannot go wrong with the comprehensive offering of Soft Starters designed and manufactured by Siemens that you can purchase from Kempston Controls today, including the new and improved SIRIUS Soft Starters. Contact Kempston Controls today to discuss your Siemens Soft Starter Requirement.

Check out the range of Siemens Soft Starters available at Kempston Controls

Kempston Controls

Kempston Controls is committed to finding you the ideal solution for your application. Call us today on +44 (0) 1933 411 411, email us at, or alternatively contact us here, we will be happy to help.

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