However, supplying a 3-phase motor with a single-phase power source is quite complex and produces some drawbacks and dangers.
Below you will find basic information about the implications, methods, and considerations of the instrument.
Understanding the Basics
A 3-phase motor operates using three out of phase currents that are 120 degree phase shifted in order to develop a rotating magnetic field.
While a single phase supply circuit provides only one form of the alternating current, using a three phase supply therefore, with a three phase motor connected directly to the circuit without modification will prove very inefficient and in the long run could lead to damage of the equipment.
Key Considerations
Direct Connection Risks
While trying to connect a 3-phase motor to a single phase source of power can cause the motor to draw a lot of current in the windings of the motor can result to overheating, burning of the windings.
Reduced Performance
If a motor is started using a single phase supply it will run, but only at a low efficiency and with limited output power which may be 1/3 or 2/3 of the motor’s rated capacity.
Ways to Run a 3-Phase Motor with Single Phase Supply
Variable Frequency Drive (VFD)
It is able to turn single phase input into three phases output as the AC power is first rectified and then inverted back to three phase AC.
This method, apart from maintaining a proper operation, also permits necessary stabilization of the speed and doesn’t permit excessive starting current.
Recommendation: For motors greater than 3 horsepower, select an over sized VFD as recommended is to select a Variable Frequency Drive (VFD) that is doubly the motor strength3
Static Capacitor Method
This involves must be interconnecting of a capacitor between two of the motor’s windings in other to produce an artificial third phase.
Although this method is useful for periods that do not require a long term solution, it degrades efficiency and could prove dangerous when not regulated properly.
Efficiency Loss: The output power can be very low and hence this methods is not suitable for continuous use.
Rotary Phase Converter
A rotary phase converter that actually produces three-phase electric power from single-phase source and ideal for starting up several motors at once.
However, this option normally costs more for implementation and is more complicated than the VFDs or capacitors.
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