An AC winch hoist controller such as shown in the illustration has a burned out hoist contactor coil, and the coil must be replaced. Before replacing the coil, the cause for the burn-out must be determined. What statement represents possible causes? EL-0102

Correct Answer: Option C — The coil burnout may occur with a normal voltage applied to the coil (between 85% and 110% of rated voltage) if accumulated dirt prevents proper seating of the armature to the magnet.

Contactor coils operate by drawing controlled inrush current until the armature seats fully, creating maximum magnetic reactance. Accumulated foreign debris prevents complete mechanical seating, maintaining an air gap that sustains high inrush current and causes rapid thermal burnout.