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 Regenerative Power


When the load on an electric motor exerts pressure on the motor, as in braking conditions, the motor becomes a generator.  Rather than consuming electric power, it generates it.  This causes current to flow in reverse, back to the utility lines.

When a phase converter is inserted between the motor and the utility line, it must be able to handle regenerative power without damaging the converter or the load.

Rotary and static converters handle regenerative power fairly well because two of the three-phase leads are connected directly to the single-phase line. Regenerative current from these two legs flows back to the utility unimpeded. Because the third leg is loosely coupled through these converters, the power generated on this leg will likely cause a voltage rise, impeding the smooth flow of power back to the utility. In most cases, regeneration is intermittent and this unbalanced flow of power back through the converter will not create a problem.

VFDs are usually not designed to handle regenerative power. The rectifiers on input of the

VFD only allow power to flow into the device. Regenerative power will increase the voltage on the DC bus of the drive which can result in damage to the drive.  VFDs exposed to regenerative power must be fitted with braking resistors on the output side which dissipate the power as heat.  There are regenerative

VFDs which utilize IGBTs in series with an inductor as the input rectifier instead of a diode or SCR rectifier. This allows the drive pass the regenerative power back through to the utility.  Regenerative drives are relatively uncommon because of their high cost.

A digital phase converter handles regenerative power well. Two of the three-phase leads are connected directly to the single-phase line, allowing this power to pass through unimpeded. Even though the third leg utilizes a double conversion system, the rectifier is an IGBT in series with an inductor. This allows well-regulated regenerative power to pass through to the utility on the third leg.