A Rotary Phase Converter is designed to create three-phase power from a single-phase power source. Unlike a Static Phase Converter (that only STARTS a three-phase motor), a Rotary Phase Converter will RUN your equipment continuously and get to its full horsepower potential.
The Rotary Phase Converter system is made up of an idler generator and a control panel. Your start capacitors and run capacitors go inside this control panel, as well as any of the switches and relays.
By hooking your 3-phase motor to an idler generator and capacitors, you will get a 3-phase power source even though only 1-phase power could be coming from your utilities. Your idler needs to have at least a 20-30% higher HP rating than the motor that you are trying to run.
So, how do Rotary Phase Converters work? Single-phase power energizes a three-phase idler generator by giving it two legs’ worth of power. Start capacitor will give the idler motor a third leg to get it working and a run capacitor will balance the phases out in order to provide your motor with a clean and reliable 3-phase power.
Rotary Phase Converters working
Rotary Phase Converter is made up of a 3-phase idler generator (or motor without external shafts), and a bank of capacitors wired together to work as a single large capacitor. Here is the schematic diagram:
From the diagram, you can see that the converter is receiving power from a single-phase two-line power supply (to produce two-thirds of the phases required), and the Rotary Phase Converter creates the third line of power.
Rotary Phase Converter’s idler motor needs a boost (a third leg) in order to get going. This can be done by some kind of another mechanical device (another motor, for example) or the use of the capacitor’s provided rotating magnetic field to start the converter (also known as start capacitors).
Once running, the three-phase idler motor will run on two legs of a single-phase power supply and generate the third phase in the process. This will give our equipment 2 phases from utilities and one phase from the third leg of the motor winding.
These three lines will be connected to our three-phase machine motor and it will start and run just as it would on three phases from the utility company. Run capacitors need to be sized properly as well in order to supply perfectly balanced 3-phase power at 120 degrees.
To operate Rotary Phase Converter, you will need to start it WITHOUT any connected load and once it starts producing power, connect your largest motor first. It can also work through the distribution center to give your whole shop three-phase power.
Three-phase motors are considered to be more efficient than single-phase, this is why they are a preferred option for shop or factory owners.