Unique Nuclear Motor Repair Solution Saves Power Plant Hundreds of Thousands of Dollars
A critical nuclear power plant in Northeastern U.S. experienced a failure during routine operational testing of a safety-related EQ motor that drives a fan in the containment fan cooling unit. The nuclear power generating facility that experienced the problem is a two-unit pressurized water reactor (PWR) that provides electricity to over two million homes in the region. The damaged nuclear motor prompted immediate action by the plant as the fan that the EQ motor was running provided the critical safety function of emergency cooling during loss of coolant accidents (LOCA) or main steamline breaks (MSLB).
Power plant technicians contacted the Schulz Electric nuclear group due to their extensive expertise with EQ insulation systems and their ability to provide emergency repair services for safety-related motors. As a stop gap measure, Schulz Electric reconfigured the plant’s spare EQ motor overnight by performing an F1 to F2 conversion. The plant installed the spare nuclear motor and sent the failed electric motor to the Schulz Electric facility for failure analysis and repair. During Schulz Electric’s failure analysis, experts found that the EQ electric motor was experiencing a decreasing air gap caused by cracked stator frame welds, which eventually led to stator-to-rotor contact and a subsequent trip on overcurrent during startup. The damaged welds caused the stator to become partially disconnected from the frame cage and flex inwards during motor startup where the nuclear motor is subjected to the most severe electro-magnetic forces.
After evaluation, the Schulz Electric team proposed a motor rewind utilizing their own fully qualified form-wound continuous-duty EQ insulation system, as well as a stator cage redesign and upgrade. “As an expert in nuclear motor repair, we try to not only fix problems but determine the root cause of the failure and offer solutions that can eliminate the failure mode,” said Whit Ward, a field support engineer for Schulz Electric. “The cage redesign for the nuclear motor was unique. It had to fit in the existing frame and house the existing stator core. Our engineers designed the cage to maximize the base metal contact at the welded joints, which eliminated the failure mode by distributing the electro-mechanical stresses that caused the welds to fail. So essentially what we did, was engineer out the defect in the critical EQ motor,” finished Whit.
Schulz Electric’s nuclear group specializes in nuclear motor repair. We offer a variety of nuclear services including environmentally qualified form and random wound insulation, contaminated electric motor repair with RCP electric motor overhaul and rewind, safety-related repairs, electric motor testing capabilities, high quality, cost effective solutions for MOV dilemmas, all from our nuclear motor repair facility and in-house decontamination facility.