 A 4700-kVA
3000-r.p.m. machine made in 1923 was the largest single-phase generator
that had been built. It was fitted with a new type of damper winding
developed by the Company to eliminate the troubles experienced on
the smaller two-pole single-phase machines. Another special machine
was made for the Cavendish laboratory at Cambridge, where in 1925
Kapitza and Cockcroft were carrying on early research work in nuclear
physics under Rutherford. The' Rutherford generator', as it was
known in the shops, was designed to supply a current of 72,000 A to
a small coil for the production of magnetic fields of high intensity.
Auxiliary
generating plant for use in ships included a large number of a.c.
sets made in 1920 for forty oil tankers. This was the first time
that an a.c. system had been used for marine auxiliaries, and the
equipments are giving good service on those vessels still afloat.
TRANSFORMERS
To meet the progressive increase in transmission voltages, the Company
manufactured transformers for 88-kV service in Tasmania in 1921,
for 110-kV and 115-kV service in New Zealand and Russia in 1923,
and for 132-kV service in South Africa in 1924. The South African
transformers went to the Victoria Falls and Transvaal Power Company
as part of the first order for British-made 132-kV equipment, transformers
and switchgear. This was an epoch-making event, four years before
the British grid, and the experience gained was of great value in
designing 132-kV equipment for the home market.
In 1928
when work began on the grid the Company was commissioned to build
132-kV transformers for Central Scotland. These were fitted with
on-load tap changing, which was unusual at such high voltages; a
new design of tap changer was evolved, and the first equipments
are still in service. Even higher voltages were required overseas,
a 33,000-kVA transformer group being supplied for 145-kV service
in South America.
Transformer
cooling methods began to change from water cooling to air cooling.
Water-cooled oil coolers with forced oil circulation gave place
to radiators for natural cooling up to half full load, with fans
and oil circulating pumps for mixed cooling up to full output.
In
the early days groups of single-phase transformers were used on
three-phase systems, but as the use of electricity increased and
greater capacities were required it became more economical to build
and use three-phase transformers. To solve the transport problem
a 120-ton railway truck of the side girder type was designed in
conjunction with the railway companies to enable the full height
of the loading gauge to be used. Road trailers were made to carry
similar loads so that the largest transformers could be shipped
direct to the docks.
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