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 Dual Lift Stations


Dual lift stations in municipal sewage systems are an application that often need a phase converter. They are commonly placed in residential areas where three-phase power is not readily available. The installation consists of redundant pumps with one of the pumps acting as a backup if the other pump fails or the volume to be pumped exceeds the capacity of the other pump.

The only type of static converter that should be used with these installations is a specialized type that uses auto-transformers along with the capacitors in the converter. The converter is a dual converter that is essentially two converters in one, since a static converter can be

used on only one motor load. The three-phase voltage balance is tuned to the load by adding and subtracting capacitors and by changing taps on the transformers. The voltage balance is good as long as the load does not change, but even modest changes in the load result in serious voltage imbalance for a motor operating at its rated capacity.

Rotary converters are not a good solution for dual lift stations. Because the load changes dramatically as the pumps switch on and off, voltage balance is a problem.

The inefficiency of the converter is a major drawback since the converter is likely to be running most of the time, and

configuring a system to turn the rotary converter on and off also complicate the installation. Phase converting VFDs can be used in these installations with a separate VFD for each pump. Since a VFD cannot be used as a power supply, standard control panels for dual lift stations cannot be used.  The VFD must be wired directly to the motor leads, not to the input of a standard pump panel.

A digital phase converter can power one or both pumps with perfect voltage balance. It can be used as a power supply, providing power to the standard pump panel. A digital phase converter can remain constantly powered, using very little power when on standby, or can easily be configured to turn on and off automatically.