Colin McDonnell asks about soft starter use and any energy benefits. His question is answered by the ABB (Theme - Electrical Control):
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Question: I have a customer who has asked whether there is an energy benefit associated with softstart units over DOL starting for a 38kW submersible pump. Is there?
I would have thought that a lot of the motor starting surge is reactive and thus not reflected in kWh energy usage. The real power needed to get the load up and running must be drawn regardless of the starting method used. If anything, the softstart introduces a slight energy penalty while it is in circuit because its own losses.
I would appreciate an expert opinion, though.
Answer: The softstarter works by gradually increasing the voltage on start up - this has the effect of a slight reduction in the initial current surge as apposed to DOL starting, and also produces a smoother start.
In normal operation, once the motor has run up to full speed, a contactor is switched in to bypass the softstart so there are no losses through the semiconductor thyristors, so the softstart is only engaged during the start period.
There may be some small power saving at start up but this is minimal.
To obtain energy efficiencies whilst running the motor, you may have to consider using an inverter drive. You could consult our drives division at Daresbury - tel: 01925 741 111.
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