An AC winch hoist controller such as shown in the illustration has welded contacts on the hoist contactor, and the contacts must be replaced. Before replacing the contacts, the cause for the welding of the contacts must be determined. What statement represents possible causes? EL-0102

Correct Answer: Option D — The welding of contacts may be caused by low applied voltage to the operating coil (less than 85% of rated voltage) or by weak springs.

Low applied voltage to an AC contactor coil reduces magnetic flux, causing armature chatter and high inrush currents that lead to severe contact arcing and welding. Similarly, overly weak contact springs fail to provide sufficient break force, encouraging mechanical contact welding.