Test an induction motor's electrical properties to avoid a sudden failure of the device it powers. Checking the motor before failure gives you time to get new parts, so you don't have to be without the device. An induction motor consists of a cylinder wrapped with wire called windings. When an electrical current flows through the windings a magnetic field flows inside the cylinder powering the motor. Check the resistance, or amount the windings limit current flow, and the motor's voltage. Compare the findings to manufacturer-specified values to decide if replacement is needed.
Turn on the power to the induction motor. Switch on the digital multimeter.
Turn, by hand, the measurement dial on the multimeter to the AC voltage setting. A capital "V" with a few curved lines on top designates the AC voltage.
Using your hand, connect the red (positive) alligator clip of the multimeter to the positive post of the motor.
Using your hand, connect the black (negative) alligator clip of the multimeter to the negative post of the motor. The reading on the screen indicates the operating voltage of the motor. The reading should be within a few volts of the value written on the motor. Turn off the multimeter.
Turn on the digital multimeter and change the measurement dial to test resistance in ohms. The ohm, the unit of resistance, equals volts per amp of current. The resistance setting is denoted by the capital Greek letter omega.
Clip the red lead of the multimeter by hand to the positive end of the motor windings.
Clip the black lead of the multimeter by hand to the negative end of the motor windings. The number on the multimeter screen represents the resistance of the inductance motor windings in ohms. This resistance should be within 2.0 ohms of that written on the motor, or the windings are damaged.
Things you need
- Digital multimeter