Index of Products

Master Highlights

Starting Methods

There are a variety of starting methods for Fire Pump Controllers, each with a different answer for how much current will be drawn when the motor is initially started. The more the reduction of the inrush current, the more complex the equipment must be.

The links below will discuss in detail each starting method beginning with the most basic, the Across the Line controller, or you may read a brief comparative summary here.

Across the Line
Wye Delta Closed

Part Winding
Soft Starting

Primary Reactor
Autotransformer

Wye-Delta Open
Variable Speed

Wye-Delta Open, Single Source

Inrush Current:
200%

Motor Starting Operation:
After receiving a start signal, our model MCO controller energizes the first run contactor and the wye contactor to connect the motor to the line in wye. The motor status starts accelerating the fire pump under the reduced voltage conditions.

At this time Master's patented Leading Phase Monitor should be checked for a leading indication. After an adjustable time delay (factory set to 7 seconds), transition takes place by de-energizing the wye contactor and energizing the second run contactor. The second run contactor connects the motor to the line in delta to finish accelerating the fire pump to its normal operating speed.

Motor Starting Current:
Once the motor is connected in wye, the motor draws 33% of its locked rotor current. As the motor speed increases, the starting current decreases according to the wye-delta speed-current curve. When transition occurs, the motor current jumps to the across-the-line current at the speed at which transition took place. From here the current quickly reduces to its normal running value.

Motor Starting Torque:
When the motor is energized in the wye configuration, the motor produces only 33% of its locked rotor torque to begin accelerating the fire pump. As the speed increases, the torque dips slightly before it rapidly increases according to the wye-delta speed-torque curve. When transition occurs, the motor torque jumps to the across the across-the-line torque and accelerates the fire pump to its running speed.