Large machines in hazardous atmospheres

The author describes UK practices in the manufacture and use of large electric machines which are for applications other than for mining. The definition of `large´ is not precise, but here the emphasis is on machines of the so-called `unit construction´ type, which are those in which the stator, bearings and overall cover are mounted on a baseplate as separate units. The paper applies to both motors and generators and the precise form of construction is highly variable. The reliability and safety of such machines has been demonstrated by their service record but recently several incidents caused the UK industry to re-examine the manufacture and use of such machines