Marthinusen & Coutts (M&C) - a division of ACTOM (Pty) Ltd- is a leading entity in the engineering and manufacturing sector, specialising in high-quality services that offer solutions across diverse industries, including power generation, mining, petrochemicals, and manufacturing.
With a strong focus on innovation and reliability, the business has established a reputation for delivering customised solutions that boost operational efficiency and performance. Their expertise covers a range of services, including repairs, maintenance, and the manufacture of specialised equipment. Committed to safety and sustainability, Marthinusen & Coutts aims to meet its clients’ changing needs while rehabilitating and extending the lifespans of critical motors and generators.
Over several years, M&C has refined the technique and process of treating windings of large alternator stators affected by partial discharge. Initially, these treatments and overhauls were carried out in the workshop, but due to high transportation costs and cross-border complications, M&C developed teams and equipment to perform this work on-site.
In 2023, following initial inspections and tests of a customer’s alternator, M&C found that the windings showed excessive partial discharge. The anti-corona layers on many line-end coils (and those nearby) were severely eroded, leading to complete slot-length erosion in several cases. This led to numerous magnetic slot wedges becoming dislodged and scattering within the machines, posing a risk of catastrophic damage. In one instance, the stator failed due to a loose wedge piece impacting the stator winding, causing a main insulation failure and a large arc hole in the stator slot.
According to Mike Chamberlain, Marketing Executive at M&C, in 2024, the customer requested that M&C complete the stator winding rehabilitation works on the other 17 identical generators and address any issues they might encounter during the alternator overhaul and stator winding rehabilitation. The M&C team has been working on this project since 2024, and we have completed the refurbishment of 14 units so far, each taking about 48 days.
Two factors make this a unique, proprietary, M&C process.
One is that it is a new, original procedure devised by M&C engineers and the technical team, in collaboration with international insulation specialists and the owners of the machines involved. It uses existing materials, but in a manner that has not (to our knowledge) been applied previously.
The second factor is that the method has now been successfully applied to over 35 machines. The technique has also been validated, as each stator has completed a full one-minute High Potential Voltage Test at 23kV RMS (Root Mean Square), demonstrating the process’s effectiveness. To provide perspective, every stator coil is subjected to 23,000V RMS to earth to verify the insulation’s integrity after treatment. Partial Discharge tests have also been carried out on many units, both before and after applying the treatment.
Developing the process was an achievement in itself, and executing this treatment on site was also a notable accomplishment under the guidance of M&C’s Field Service Manager, Owen Killian.
M&C has also gained the advantage of implementing the procedure many times, so they can now be considered specialists.
Furthermore, M&C has also completely rewound one stator that failed before the insulation treatment could be applied; due to the winding configuration and the high rated voltage of 15kV, this was an achievement in itself.
M&C has once again successfully demonstrated its ability to design innovative solutions that enhance reliability and prolong the lifespan of customers’ electrical rotating machines under tight time constraints.