When checking windings on a three phase motor, what should the resistance readings show?

The correct understanding when checking the windings on a three-phase motor is that the resistance readings should ideally show consistency across all three windings. This consistency reflects that the windings are in good condition and have not developed any faults or significant differences in resistance that could lead to imbalance during operation.

When all resistance readings are the same, it indicates that the motor windings are intact. If one winding reads low, it suggests that there could be a short circuit or other significant issue in that particular winding. This can lead to an uneven load on the motor, causing it to run inefficiently or even fail. Therefore, while it might seem acceptable to have a low reading for one winding in specific scenarios, such conditions typically indicate a problem rather than normal operational parameters.

The option suggesting that only one winding should read low is indicative of a fault condition, which is not ideal in the context of ensuring the motor is functioning properly and safely. Thus, it is preferable for the resistance readings to be uniform across all three phases to ensure optimal performance of the motor.