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

Primary Reactor, Single Source

Inrush Current:
50% tap = 300%
65% tap = 390%

Motor Starting Operation:
After receiving a start signal, our model MCR controller energizes the start contactor to place the reactor in series with them otor and power source. This added series reactive impedance increases the total circuit impedance and decreases the power factor thereby reducing the starting current and real power drawn from the power source.

Once connected to the power source through the reactor, the motor starts accelerating the fire pump under recuded voltage conditions. After an adjustable time delay, factory set to 3 seconds, transition takes place by energizing the main contactor. When the main contactor closes, the reactor is bypassed by applying full voltage directly to the motor. The reactor remains connected during transition to maintain a closed transition operation. When the reactor is completely bypassed, the fire pump accelerates to its normal operating speed.

Motor Starting Current:
Once connected to the line through the 50% or 65% reactor taps, the motor respectively draws 50% or 65% of its locked rotor current. As the speed increases, the starting curreent decreases according to the reactor speed-current curve for the tap selected. When transition occurs, the motor current jumps to the across-the-line current at the speed transition took place. From here, the current quickly reduces to its normal running value.

Motor Starting Torque:
When energized through the 50% or 65% reactor taps, the motor respectively produces 25% or 42% 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 reactor speed-torque curve for the tap selected. When the transition occurs, the motor torque jumps to the across-the-line torque and accelerates the fire pump to its running speed.