What is the usual expression for time ratings in electric motors?

The usual expression for time ratings in electric motors is typically in hours. This is because electric motors are designed to operate for extended periods, and their performance is evaluated based on continuous usage. The time rating helps in understanding how long the motor can run without overheating or suffering from wear and tear.

While minutes and seconds may pertain to short-duration testing or specific applications, the standard industry practice favors hours as the most relevant metric. This allows for a more practical assessment of the motor's durability and operational efficiency during typical service. Days are also not a common measure for motor ratings, as they exceed the practical evaluation time frame.