 As applied
to electric traction, the metadyne changes the constant voltage supply
from the line into a variable voltage supply for the traction motors,
giving a continuously variable transformation ratio and keeping
the output current constant. It thus takes the place of resistances
for limiting the starting current, and it also permits the train to
be stopped by regenerative braking. Over a hundred metadyne equipments
were put into service on London Transport trains between 1938 and
1940, and they are still in successful operation. During the war,
the metadyne was further developed as a power amplifier.
An
unusual method of a.c. traction—the Kando system—was
adopted by the Hungarian State Railways in 1931. The Company received
an order for motors and control gear for twenty-six locomotives,
which were to be equipped with 2500-hp three-phase motors fed through
phase converters from a 16,000-V singlephase supply. The M-V equipment
was transported on English railway trucks all the way from Manchester
to Budapest, 1300 miles in ten days.
Trolleybus
electrical equipment was first investigated round about 1930, and
designs for lightweight trolleybus motors were developed. Within
a year or two the trolleybus showed signs of becoming an effective
competitor to the tramcar and the motorbus. The M-V motor had a
single-turn armature winding and a low speed full field characteristic;
the design concentrated on obtaining the best possible commutation
and foreshadowed many features of the present-day motor. Robust
forms of control equipment of the unit switch type were developed
between 1933 and 1935, first electromagnetic and later electropneumatic,
and systems of regenerative and rheostatic braking were worked
out, the latter becoming the more popular, Other innovations had
been made available: an m.g. set for low voltage lighting, having
a single shaft but double insulation between motor and generator;
provision for manoeuvring the vehicle on the lighting battery; and
coasting and run-back brakes to prevent it from running away downhill,
forwards or backwards.
The
first commercial venture came in 1933 when sixteen sets of equipment
were supplied to the South Lancashire Transport. Then London Transport
decided to replace all the trams north of the Thames with trolleybuses,
and in 1934 the Cornpany was asked to design electrical equipment
for the prototype three-axle vehicle, Today the London Transport
Executive operates a fleet of 1780 trolleybuses with 1400 motors
and 900 control equipments of M-V design or manufacture.
The success of the initial equipments caused trolleybuses to be
adopted by other towns, and the use of M-V trolleybus equipment
increased rapidly. By 1936 the Company had become the leading supplier
to British undertakings and was making about 40 per cent of all
trolleybus electrical equipment manufactured in this country, a
position it still holds.
RAILWAY SIGNALLING
Power signalling apparatus, in addition to being manufactured at
the TrafFord Park works, was now largely designed there owing to
the difference between British and American standard practice, and
many contracts were undertaken for
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