Three Phase Motor Wiring Diagram Using Single Phase Supply Connection

Work & Installation (Input → Output,)

• Single-Phase AC Supply: Connect live (L) and neutral (N) wires to the motor circuit.
• Capacitor Connection: Connect the start/run capacitor between the main line and one motor terminal to create a phase shift.
• Motor Terminals: Connect single-phase live and neutral to two of the three motor terminals (usually U & V). The third terminal (W) connects through a capacitor.
• Overload Protection: Install a thermal overload relay or MCB in series to protect the motor.
• Earthing: Properly earth the motor frame for safety.
• Operation: Turn on the supply. The motor starts with reduced torque and runs safely for light loads.
• Output: Three-phase motor runs on single-phase supply with temporary or small load applications.

Testing & Final Adjustments

Wire the supply after which the supply should be switched on, and after switching on, ensure the motor starts running without unnecessary noise or vibration. Measure the voltage over each motor terminal so that there is good phase formation. Make sure that the capacitor is of the proper type by kVA and operating voltage of the motor. Test Operating by checking to make sure that the overload protection (MCB or thermal relay) is operating on a test condition of being tripped when overloaded. Look at all connections to ascertain their tightness and insulation, and correct earthing. To ensure that the motor does not overheat, test-run the motor within a short period because using the three-phase and single-phase motor in the same system decreases the efficiency and increases the amount of heat. Frequent control guarantees safety, balance of the phase, and eliminates the harm to the motor. The technique is only appropriate when it is used temporarily or when it has light loads; constant heavy-duty operation must have a legitimate three-phase supply.