What instrument is used to detect breakdown in the internal windings of an electric motor?

The correct instrument for detecting breakdown in the internal windings of an electric motor is a megger, or insulation resistance tester. This device measures the insulation resistance of electrical equipment and can help identify issues such as short circuits or insulation failures within motor windings.

When testing an electric motor, a megger applies a high voltage to the windings while measuring the resistance. A low resistance reading indicates that the insulation may be compromised, which can lead to breakdown or failure of the motor. This makes the megger specifically suitable for assessing the condition of the insulation in windings, allowing for preventive maintenance decisions.

While a multimeter is useful for measuring voltage, current, and standard resistance, it may not be able to apply high enough voltage to effectively test the insulation resistance of motor windings. An oscilloscope can analyze waveforms and diagnose signals but does not provide a direct measurement of insulation resistance. A wattmeter measures electrical power in a circuit, which is not specifically helpful for diagnosing winding integrity. Thus, the megger stands out as the appropriate tool for identifying breakdowns in electric motor windings.