Phase Converters & Power Factor
Phase Converter Efficiency
Installing a Phase Converter
Rotary Phase Converters
Static Phase Converters
VFDs as Phase Converters
     • Harmonic Distortion
Three-Phase Motors
Phase Converters & Voltage Balance
Phase Converter Applications
     • Submersible Pumps
     • Woodworking Equipment
     • Dual Lift Stations
     • Phase Converters & Welders
     • Phase Converters & CNC Machines
     • Phase Converters & Air Compressors
     • Phase Converters & Elevators
     • Phase Converters & Wire EDM
     Phase Converters & HVAC
Phase Converters & Transformers
     • Step-up Transformers
     • Buck-Boost Transformers
     • Isolation Transformers
Phase Converter Experts
Digital Phase Converters
Regenerative Power
Three-Phase Power
     • Delta vs. Wye Configured Power
Motor Starting Currents

Phase Converters and Submersible Pumps


Three-phase submersible pump motors typically demand very well balanced three-phase power in order to operate safely. The pump motor must be small enough to fit in a well casing deep underground, so space is at a premium. Oversizing the motor to keep it lightly loaded and help it withstand voltage imbalance is expensive and may not be physically possible. Consequently these motors usually operate at maximum capacity and are very sensitive to voltage imbalance.

Submersible motor manufacturers like Franklin Electric may even void the warranty of their motors if specified voltage balance is not maintained by the power supply to the motor.

Static phase converters should never be used to power submersible pumps because of their poor voltage balance. There are special static converters that incorporate auto transformers which allow the voltage balance to be tuned to a load. These can be used with submersible pumps as

long as the load on the pump does not change. Even slight load changes result in significant voltage imbalance with these converters.

Rotary converters can be used to power submersible pumps with certain restrictions. The converter is usually oversized by a factor of two or three times to help maintain voltage balance and to provide current for starting. Most pump motor manufacturers will not allow the motor to be operated into its service factor on these types of converters because of the potential for motor damage from voltage imbalance. Rotary converters also present a challenge in this type of application because the pump almost always operates on an automatic signal from a pressure or float switch. In this case, the rotary converter must be left running, which wastes electricity, or configured to turn on automatically before the pump, then turn on the pump after a few seconds delay.

Variable frequency drives (VFD) can be an effective phase converter for submersible pumps with some restrictions.  If a drive with a three-phase input is used,

it must be derated by one half (use a 20 HP drive on a 10 HP motor).

And because the output of the drive is not a sine wave voltage, if the distance between the drive and the pump motor is too great, dangerous voltage rise can occur. Filters on the output of the drive can be added to mitigate the harmonics, allowing longer lead lengths for deep well applications. Because the drive is connected directly to the pump motor leads, there is no need for a three-phase pump panel to start and protect the motor. The drive will also start the motor by slowly ramping up the motor speed, eliminating line disturbances on the single-phase line.

Digital phase converters are a good choice for operating submersible pumps because they maintain perfect voltage balance under any load condition and with sine wave voltage, lead length between the converter and the pump motor is not an issue. Digital phase converters can also be configured to start and protect the pump, eliminating the need for a three-phase pump panel.