Sutton's Locomotive Workshop British Railways Sulzer Type 2 Operating Manual - page 10
Control Equipment
The control unit is mounted in a dust-tight compartment in the body of the locomotive
at the generator end of the engine room. It is thus convenient for cable runs and at the
same time away from engine piping. On this control frame are located all the
contactors, relays and switch devices. Separate contactors are provided in each motor
circuit. The reverser is of the butt contact type, having silver-faced main contacts; it
is electro-pneumatically operated.
The driver’s control equipment comprises a master controller and instrument
panel, in each cab, together with alarm identification panel, engine instrument panel,
lighting switch boxes and fire alarm unit.
The battery is contained in four pull-out boxes suspended from the underframe.
With the engine running, it floats across the 110 Volt supply from the auxiliary
generator, controlled by a Brown Boveri sector-type regulator.
Control Scheme
The characteristic of the combined generator-exciter unit is that of the well known
three-winding generator. The exciter had a differential series winding which carries
the main traction current, and also a separately excited winding which is externally
controlled both by the driver’s controller and the automatic load control. Due to the
low value of excitation current in this small machine, small control devices can be
employed. The shape of the characteristic is the familiar drooping curve, the
excitation being proportioned so that there is a definite maximum limit to the current
which can be delivered to the traction circuit at standstill, and so that at this point, the
demand on the engine is less than its rated output. The section of the characteristic
which intersects the contact HP curve of the engine is artificially controlled by
varying the separate field of the exciter by means of a rheostat.
This rheostat is controlled by an oil servomotor which is incorporated in the
engine governor. This arrangement automatically varies the generator loading so that
it agrees with the predetermined engine output at any particular engine speed. The
four traction motors are connected in parallel across the main generator with two
stages of motor field weakening.
Complete control of the main traction equipment is obtained by a self-lapping air
valve operated from the master controller. On moving the power handle away from
the ‘O’ position, the load regulator first runs up, increasing the excitation and therefore
tractive effort. At a certain point, the main engine characteristic is reached and
thereafter, engine speed and power rise together, until the full rated HP is reached.
The scheme covers the control of tractive effort at starting and of locomotive power
afterwards, all without the use of ‘notching’ contactors.
Maximum tractive effort is reached at a very low engine speed so that racing the
engine to start the train is completely unnecessary. Field weakening is introduced in
stages initiated by the generator load regulator.
Protective Devices
The protective devices provided on this locomotive are of two types: (1) apparatus
for the safety of the locomotive in traffic; (2) apparatus to protect the engine and
transmission equipment.
Under category 1 there is the deadman’s pedal with its corresponding push-
button on the opposite side of the cab, which permits the driver to cross the cab to
observe signals. Also air-operated switches are provided to prevent the locomotive
from being driven until there is sufficient compressed air and vacuum to operate the
locomotive and train brakes. In addition, the new BR type of automatic train control
is fitted.
Protective devices in the second category include provision for the engine to be
automatically stopped in the event of low cooling water or lubricating oil pressure,
and the appropriate latched relay operates on the identification panel of the locomotive
affected. An ‘engine-stopped’ light at the driving position indicates if any one engine
is stopped when running in multiple unit. This alarm also serves as a guide when
starting engines on locomotives couple in multiple, since the start push-button is
merely held depressed until the ‘engine-stopped’ alarm becomes normal.
Earth leakage causes the earth leakage relay to operated and the traction circuit to
be opened. Provided the earth fault has cleared, the relay can be reset by moving the
SLW Class 24 Operating Manual
Page 19
Page 18
SLW Class 24 Operating Manual