Marthinusen & Coutts, a leader in the repair and maintenance of rotating electrical assets, is one of a handful of companies worldwide capable of rewinding large salient pole type rotors where the poles cannot be removed from the shaft. This capability recently attracted an enquiry from Kasese Cobalt Company Limited in Uganda who called on M&C to evaluate and carry out the repairs necessary to restore an AVK 3889 kVA synchronous generator that had been damaged by a lightning strike.

M&C CEO Richard Botton visited the mine site at Kasese, 420 km west of Kampala, where he determined that the exciter had blown. Based on the technical complexities of the task, Botton recommended that the entire unit be shipped to M&C’s facility in Cleveland, Johannesburg, for a full assessment. The company’s field service manager went to the mine to oversee the dismantling and crating of the machine to ensure that no further damage would be incurred in transit.

“At our facility, once the unit had been stripped and fully tested and assessed, we discovered that the rotor windings had interturn faults,” Craig Megannon, M&C general manager, says. “Based on this information, KCCL gave us the go ahead to refurbish the entire unit, including a complete rotor and exciter rewind.”

“The salient pole rotor design is such that the six pole pieces cannot be removed and therefore the multi-layer coils have to be wound directly onto the poles that are part of the rotor body. This can only be done using a specialised rotor turning rig that M&C has custom built. Once the unit arrives back in Uganda, we’ll send a team to supervise its re-installation and commissioning,” Megannon explains.

M&C, part of the Actom Group, was founded in 1954. Today, the company is the largest repairer and manufacturer of MV and HV electric motors and alternators in Africa. M&C also manufactures motors under licence for some international OEM’s and has more than 300 of its own designs. The company has its own design room and has invested in critical equipment such as “full load” test bays and crucial testing equipment that enable the M&C team to manufacture and repair motors with unparalleled results.