About Rotary Phase Converters

Phase converters make it possible to operate three phase equipment on single phase. This is done by the use of run capacitors to manufacture the third phase. The horsepower of the phase converter needed to operate the equipment depends on the application.

For air compressors, for example, the phase converter needs to be double the compressor motor. A 5HP compressor would need a 10HP Phase converter. If the compressor is less than 7.5 HP it would be more cost effective to use a single phase motor. Generally, single phase motors are not made over 10HP.

For most other equipment, we generally go one size more than the motor. For a machine with a 7.5 HP motor we would use a 10 HP phase converter.

Phase converters can operate multiple motors at the same time; usually 2 or 3 times the rated HP of combined HP. However, a phase converter cannot operate any one motor larger than the rated HP. A 10HP phase converter can operate multiple 10HP motors, or combined HP of 20 or more HP. But not any one motor larger than 10 HP. If a machine has a 15HP motor, a 5HP,and a 3 HP motor. We would size it as a 20HP phase converter. Not because of the total HP, a 15HP phase converter would be enough to operate the 15HP motor, plus the other motors, we generally like to go up 1 size.

The phase converter adds the third phase. The single phase in, is the same single phase out. A rotary phase converter uses a standard three phase motor as an idler motor to help balance the voltage. Additional motors in the circuit only help to balance the output voltages.

Because the single phase ‘in’, or real power is the same as leg 1 and 2 ‘out’; these leads must be used in the control circuit of the machine. The ‘manufactured’ leg cannot be used in the control circuit.

We can also build Static Phase Converters or can customize a Phase Converter to your personal needs.