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A pump starter is a soft start used in a pump motor. A soft start lessens the initial surge of current that goes into the windings of a motor when it is started, also known as the inrush current. Soft starts reduce the strain on electrical circuits of the motor.

Motor for Pump Starter

Why use a pump starter?

A pump starter can avoid pressure surges in pump applications, which can occur due to the rapid acceleration of the motor shaft. A quick start can lead to a surge of water when it reaches the top of the pipe. Using a pump starter can reduce the torque so that the water can get to the top without having it surge.

Solid state starters are the only type that allow for soft stop, which is the ability to provide controlled deceleration of the motor over a set period of time. Soft stopping prevents equipment damage or other load problems. It also prevents surges and shock waves, also called water hammer.

Shock waves come about because of the kinetic energy of the water being trapped by a check valve. The energy becomes a shock wave, traveling up and down the piping system searching for an outlet, which may cause damage to the system. A pump starter can help to dissipate the energy of the water slowly so that there is little or no energy left in the liquid to be trapped, preventing the shock wave.

Sizing a Motor Starter

The current, kilowatts and horsepower of the motor all factor into the size of the soft starter that will be required. The more powerful the motor, the more power the soft starter that will need to bring it the motor to speed.

Also affecting the required soft starter size is the starting capacity of the motor. It will be either a normal or a heavy duty start, depending on the type of load being driven by the motor.

Normal start has a load that has small or medium required starting torque, and will have a starting time that is generally less than 5 seconds. Heavy duty starts, on the other hand, have loads with a high required starting torque and will have a starting time of more than 5 seconds. The heavy duty motor will require a more powerful starter.

The more times a motor has to start up per hour, the larger the soft starter must be sized so that it can dissipate the heat generated by the thyristors. A motor that starts up and then runs continuously will not need to upsize, but an air compressor, pump motor, or other motor that may be subject to several starts in a short period of time will need to have a larger starter.

Typical Applications

Some normal duty motors that use a soft starter are bow thrusters, compressors, elevators, centrifugal pumps, short conveyor belts and escalators. Heavy duty motors that use a soft starts can include centrifugal fans, crushers, mixers, long conveyor belts, mills and stirrers.

There are very few motors that cannot use a soft start, and the manufacturer will most likely note this. Some motors may be designed for full torque at 0 RPM, and these would not be able to use a soft start.

Centrifugal Pump Starter
Bow Thruster Pump Starter
Pump Starter for Mixer
