Direct cooling of turbine-generator fields

A MAJOR IMPROVEMENT in the cooling of field windings of turbine generators has been developed by the General Electric Company and applied for the first time in a 125,000-kva (30-pounds-per-square-inch-gauge hydrogen pressure) 3,600-rpm turbine generator now in the Huntley Station of the Niagara Mohawk Power Corporation at Buffalo, N. Y. Figure 1 shows the field of this machine. The new cooling arrangement has been proved successful in factory tests, which showed that at full 30-psig capacity, the temperature rise of the field winding is only about 25 per cent of that of otherwise duplicate fields of standard design previously tested. This indicates that for the same temperature rise, the new field could have its 30-psig capacity doubled, to 250,000 kva. Because of a requirement that the generator field be interchangeable with the fields of several previous machines of the same capacity, it was not feasible to take advantage of the improved cooling to reduce the physical size of this particular generator.