Some of the loads we use every day exhibit high inrush currents when they are first turned on. An incandescent lamp with a cold filament can draw almost ten times its normal operating current on startup. I took a snapshot of the inrush current in a 500-watt PAR 64 using a Fluke 43B power quality meter. It measured a peak inrush current of 41 amps at 120V before it settled down to 5.7 amps in half a second. Discharge lamps also have a large inrush current. I measured it in a 575-watt MSR lamp fixture at 20 amps at 120V, settling down to 7.1 amps in 0.6 seconds. Chain hoists and other motors also produce high inrush currents. The chain hoists that we most often use in this industry are induction motors. When they are started from a stand still, it requires a lot of torque to start lifting a load. Even if they are lowering a load with the aid of gravity the windings still have to be energized before the motor will start moving. A 1-ton CM hoist can draw as much as 30 amps at 230V on startup before settling down to 11.4 amps (3.8A 3-phase) in about half a second.
From "Focus on Fundamentals" by Richard Cadena, PLSN, July 2010
