Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

Which meter is typically used to bench check a motor for shorts or open windings?

1. Voltmeter

2. Ammeter

3. Ohmmeter

4. Capacitance meter

The correct answer is: Ohmmeter

The use of an ohmmeter for bench checking a motor for shorts or open windings is based on its ability to measure resistance in electrical components. When examining an electric motor, it's essential to check the winding resistance to identify potential issues. By using an ohmmeter, a technician can determine the continuity of the windings; if an open winding is present, the resistance reading will be infinite, indicating that electricity cannot flow through that path. Conversely, if there is a short circuit between windings, the resistance reading will be significantly lower than expected, suggesting a fault in the motor. This tool is particularly suited for this kind of diagnostic testing because it provides a clear indication of winding health without needing to power the motor, which could lead to further damage or injury if improper conditions exist. In contrast, other meters like voltmeters or ammeters measure voltage or current during operation, which is not ideal for identifying issues in windings without first checking their resistance. A capacitance meter, while useful for testing capacitors in the circuit, does not provide the necessary information about the continuity or integrity of motor windings.