How to Calculate Three Phase Motor Current Using Motor Winding Resistance
- 1). Use a volt meter to measure the incoming three-phase voltage. The voltage can be measured at the motor's brushes by turning the voltmeter dial to the correct voltage range and touching the probes to the motor's power connection.
- 2). Confirm the motor winding resistance using a multimeter. The resistance can be measured by holding the probes of the volt-ohm meter on the brushes while the power is off.
- 3). Use Ohm's Law to determine the current. Current flows on the surface of a conductor (like a motor winding) from negative to positive and is expressed in amperes, or amps. Divide the voltage by the motor winding resistance to determine the current used.
If the voltage is 240 VAC and the motor winding resistance is 15 ohms, the current used is 240 / 15 = 16 amps.
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