An unloaded start of a motor is exemplified by starting a centrifugal air ______.

• A. Fan
• B. Compressor
• C. Pump
• D. Blower

Answer: (B)

Starting a motor with almost no mechanical load on the shaft keeps the current draw low and lets the motor accelerate quickly without stalling. A centrifugal air compressor is the classic example because, if you start it with no air being delivered (discharge valve closed or system valve shut), there’s very little back-pressure and the impeller meets almost no resistance. The motor can spin up to speed with minimal torque required. Only after reaching the design speed is the load added as air is compressed and delivered to the system.

Other options would impose more immediate resistance when starting, even if valves are temporarily closed, so they don’t illustrate an unloaded start as cleanly.