Marthinusen & Coutts, a division of Actom, recently completed the rebuild of a 6 550 kW 2 pole
11 000 Volt squirrel cage induction blower motor for a copper mine in Zambia. According to Rob Melaia, engineering and technical executive at Marthinusen & Coutts, the motor had suffered a rotor failure which caused collateral and associated damage to the stator and also considerable damage to the rotor laminations at the core extremities.

Marthinusen & Coutts has extensive experience with the rebuilding of such large rotating machines and it is this ability to leverage knowledge gained from years in the industry that facilitates the identification and repair of electrical machinery in limited time.

The repair work undertaken comprised a stator rewind, a rotor rebar including a partial recore with new laminations and the replacement of the P900 high strength rotor retaining rings.

Interestingly, the retaining rings are made from the same steel used for the largest turbo generator in the world and this was sourced by Marthinusen & Coutts from a leading German supplier in record time. “Working closely with our network of local and international partners facilitates access to specialists in all fields and allowed the fast track procurement of these specialised rings. This was especially impressive as these were procured over the Christmas period,” Melaia says.

The rotor rebar involved new rotor bars using high resistivity brass alloy and the redesign of the rotor cage axial locking system.

Once the rebuild has been completed, the motor was tested at Marthinusen & Coutts’ facility which houses the third largest high speed dynamic balancing machine in sub-Saharan Africa.

“We were able to perform high speed balancing as well as a full no-load run test to verify vibration and bearing integrity condition performance,” Melaia says.

Marthinusen & Coutts is Level 3 BBBEE rated, ISO 9001 accredited, holds SANS 1561 LV motor repair, SANS IEC 60079-0/1 flame proof and SANS IERC 60079-15 non-spark permits and has been awarded a five-star NOSA rating. With five production workshops covering 30 000 m2 under roof in southern Africa, Marthinusen & Coutts is conveniently located to provide customers with a fast turnaround on repairs and upgrades on all rotating equipment.