What can be checked when using an ohmmeter on a transformer?

Using an ohmmeter on a transformer primarily allows for checking the coil resistance of the transformer windings. The resistance values obtained from measuring the windings help in assessing the condition of the transformer. By measuring resistance, you can identify any potential issues such as shorted or open windings. A significant deviation from the expected resistance value can indicate faults that may lead to operational failures or reduced efficiency.

This measurement does not provide information about the turns ratio, which requires a different testing method called a turns ratio test. Additionally, measuring the output voltage levels necessitates the use of a voltmeter rather than an ohmmeter, as voltmeters are designed to measure the potential difference in live circuits. Insulation resistance checks also involve a specialized insulation resistance tester, which applies a high voltage to ensure the integrity of the insulation, while an ohmmeter measures only the resistance of the windings themselves during a non-operational state. Thus, checking the coil resistance is the fundamental measure you can perform with an ohmmeter on a transformer.