Should you run a motor at the service factor for extended periods?

Should you run a motor at the service factor for extended periods?

• A. Always
• B. Only for short periods
• C. Never
• D. For continuous load

Answer: (B)

Service factor shows how much extra load a motor can handle for short moments beyond its rated capacity. It’s a built-in margin for temporary overloads, not a setting for normal operation. The reason is that running at that overload continuously causes more heat in the windings and bearings, pushing the motor toward temperatures above what the insulation and cooling system are designed to handle. Over time this accelerates insulation aging, shortens motor life, and can trigger overheating protection or failure. Therefore, the best practice is to use the service factor only for brief periods, such as transient spikes or short-start/load surges. If you need to run near that level for longer, you should choose a motor with a higher service factor or one that's appropriately oversized for the continuous load.

Service factor shows how much extra load a motor can handle for short moments beyond its rated capacity. It’s a built-in margin for temporary overloads, not a setting for normal operation. The reason is that running at that overload continuously causes more heat in the windings and bearings, pushing the motor toward temperatures above what the insulation and cooling system are designed to handle. Over time this accelerates insulation aging, shortens motor life, and can trigger overheating protection or failure.

Therefore, the best practice is to use the service factor only for brief periods, such as transient spikes or short-start/load surges. If you need to run near that level for longer, you should choose a motor with a higher service factor or one that's appropriately oversized for the continuous load.