Marthinusen & Coutts (M&C) recently manufactured four new field coils and poles for a 25 MVA generator at a hydroelectric power station in Cameroon. The new field coils and poles were needed because the originals had been stolen from a 24 600 kVA 36-pole generator in the 264 MW Edéa power station on the Sanaga River near the town of Edéa in Cameroon.

The client provided rough dimensions, which necessitated a visit to the power station by two of the firm’s senior technical staff members to obtain more accurate dimensions and useful photographic evidence.

The need to physically visit the power station to obtain accurate dimensions and photographs, together with a complex field coil design, added to the difficulty in manufacturing the replacement parts.

The complex field coil design consisted of a double-bank series coil with a unique method of connection between the north and south poles. Another unusual feature was that the copper dimensions required on-edge bending to wind a continuous coil.

Although the company is often called upon to manufacture items by applying reverse engineering procedures when the OEM’s design drawings for the equipment are unavailable, they are usually able to gain access to the original component itself to work from. But not in this case since the original parts had been stolen.

A crucial part of the whole process was the design and manufacture of the tooling and jigs required for the manufacture of the coils and poles. The parts were manufactured at the company’s Power Generation & Large Motor facility in Benoni, having prepared the necessary designs mainly on the strength of the photographs they had been provided with.

The contract was completed on schedule at the end of September.