 Electrical
equipment for Sperry gyro-stabilizers had been manufactured in 1921
for a British destroyer, H.M.S. Vivian, and in 1931 the first passenger
liner, the Conte di Savoia, was successfully equipped. The system
is that any rolling of the ship is detected by an auxiliary gyro,
which causes the main gyro to counteract the torque caused by the
sea. On the Conte di Savoia there were three stabilizing gyros, each
driven by a 560-hp squirrel cage induction motor; it took an hour
to bring the 110-ton gyro rotor up to its effective (normal) operating
speed and an hour and a half to reach the maximum speed of 910 r.p.m.
Electric
motors of the medium and smaller sizes made a spurt forward in 1930,
when long-term experimental work began to mature. New designs, in
which D. B. Hoseason and later H. West had taken a great part, were
produced, and partly as a result of the earlier air flow investigations
these showed a great saving of material for a given output. *
A.c.
motors were provided with axial ventilation through the stator and
rotor punchings, which were designed for the most efficient transfer
of heat; ball and roller bearings were assembled in cartridge type
housings, and small air gaps, stiff shafts, and former-wound coils
fitted in half-open slots were employed. From this basic design
came a new form of totally enclosed fan-cooled motor—the double
air circuit type—flameproof motors, and many other adaptations.
By 1932 motors had been designed and made for the higher voltages
up to 6600, and two years later an economical design was available
for the smaller sizes down to 20 hp 3000 V and 200 hp 6600 V. The
double air circuit design was a great advance; at once the old maximum
rating of about 75 hp for totally enclosed motors was far exceeded,
and it is now used for motors up to 1000 hp.
D.c.
motors had the novel features of double-ended ventilation, ball
and roller bearings with cartridge type housings, and metal spools
for the field coils (helping to cut out hot spots). A new design
was made for crane service and was later adapted for flameproof
enclosure. For industrial use, d.c. totally enclosed machines were
produced with radiators mounted above and below the motor.
The
new designs of standard motors were quickly followed by developments
in steelworks motors (including live roller motors), synchronous
induction motors with overhung exciters, flameproof conveyor and
coal-cutter motors, flameproof motors for the oil industry (including
large totally enclosed fan-cooled machines), steel frame motors
for gold mining work, and large motors for boiler feed pumps.
Control
gear developments kept pace with the growing complication of industrial processes, and an increasing number of special equipments
embodying all sorts of automatic features were designed and manufactured.
Examples are 1000-hp and 2000-hp Ward-Leonard control equipments
supplied for push benches at a Corby tube works, large d.c. contactor
boards supplied to an Ebbw Vale steelworks (including Ward-Leonard
equipment for an 800-hp skin pass mill and a
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