A rotary phase converter -- also referred to as RPC -- is a machine that converts power from an alternating current system of one phase to an alternating current system of a different number of phases of the same frequency. It is used in conjunction with the capacitors.
A RPC constitutes an electric motor or an electric motor generator, connected together mechanically on the same shaft via gears. It is built using a static phase converter and an idler motor.
A RPC works on a simple mechanism, and is one of the most simplest, reliable, and cost-effective methods available for converting single phase power to three-phase power. It lasts for at least thirty years and weighs around 300 to 400 lbs. For building a RPC, sound knowledge of electricity and motors is a must.
Steps for Constructing a Rotary Phase Converter
The equipment required to build a RPC are: a three-phase motor, delta wound, wire pliers, wire strippers, screwdrivers, plastic wire connectors, and black plastic vinyl tape.
Count on the amount of horse power that you want to run from the RPC. The total load should not exceed 80% of the rated load for the phase converter. For example, if load calculation is utilizing 10 hp, phase converter should run up to 8 hp in load.
The next step is the connection of the RPC. It's an easy task once you have figured out the amount of load. A proper sized capacitor according to the demand of the load should be placed on the motor circuit. The capacitor should be filled with oil. Experimentation is required for proper tuning of the capacitor with the circuit.
The termination of RPC should be done using only 240 volt power. The motor which is to be used as a converter should be first wired as a 240 volt connection. There are three terminals numbered as L1, L2, and L3. They are numbered arbitrarily. These terminals are addressed as legs.
Connect one power lead to L1 and the other to L3. The power capacitor should be tied between L1 and L2. This leads to three-phase power from the converters motor lead.
Commence the phase converter with a normal motor starter, for a single phase operation. The three-phase motor starter can be connected from three leads of motor itself. For fine performance, phase converter must be running, before any load is attached to the rotary phase motor circuit.
- Connect a single phase power of 230 volts to the supply terminals T1 and T2 of the motor you are using as a converter.
- In order to start the motor, spin it. It does not have the ability to start on its own.
- Take the three-phase power off the terminals T1, T2, T3 .
With these methods, you can convert a single phase to three-phase electrical power, thus, building a RPC which will draw more power than its capacity.