The equipment to be repaired was a 40 year old motor generator set. The unit could not be replaced because of its unusual design and complexity. A full strip and survey was carried out to find the cause of failure and recommendations made to bring the unit back to a serviceable condition.
This MG set has a DC motor and DC generator mounted onto the same shaft and within the same housing. The frame is designed so it can be split horizontally at shaft level and the armature removed. This is necessary when the available space around the equipment is limited and the access size for removal is small e.g on board Ships with fixed hatch sizes.
An electrical check of the machine showed that both armatures and some of the field coils needed to be replaced. Without the original drawing, it is necessary to perform a careful dismantling of the coils to ensure that the full winding specification is recorded. There were parts missing for the fan assembly and terminal box connections.
The brush gear and commutators were in a poor condition due to carbon and corrosion. The brush gear consists of a rocker ring, brush arms, and brush holders. All these parts must be thoroughly cleaned or bead blasted to return them to the best condition. The commutators are skimmed and undercut to reveal the original copper finish and then the armature is precision balanced.
Once the rewinding was completed, the coils and armatures were tested before being re-assembled into the housing which had been grit blasted and painted. Our standard practice is to replace all bearings, brushes, seals, gaskets and fixings along with any missing parts that are re-engineered manufactured to suit.