The Diesel-Alternator has been included to provide a stand-by supply of 415 volts and 250 volts AC at 50 Hz if a Motor-Alternator Set should fail, or if the train has to be towed.
The output of the Diesel-Alternator is 250 KVA with the same tolerances on voltage and frequency as the Motor-Alternator Set, due to its output being lower than the M-A certain non-essential loads are shed when the D-A Set is in use. Inter-locking is provided to ensure that both alternators cannot be connected to the supply lines at the same time.
There is a small control panel at the driver's left hand side for control of the M-A and D-A sets. It consists of an on and off switch with indicator for each M-A set Local/Remote and for each D-A set Local/Remote.
M-A and D-A Control Panel in APT-P Cab.
APT-P Diesel-Alternator Set, located in the equipment bay of the Driving Trailer.
The Diesel engine is a 4 Stroke, In-line, 6 Cylinder, Turbocharged CUMMINS NTA 855-G. A hydraulic governor is used to enable the speed (1500 r.p.m.) of the engine (and consequently the frequency of the alternator supply) to be maintained within close limits. It is started by compressed air from the main train air line.
COMPONENT IDENTIFICATION LEGEND
The Alternator is of the brushless type 5800 made by NEWTONS of Derby. It provides 3 phase, 415 volt Alternating Current at 50 Hertz when rotated at 1500 r.p.m. with an output of 250 KVA.
As the Diesel-Alternator is of a lower rating than the M-A Set the full train load cannot be taken, therefore certain loads are prevented from being connected to the A.C. supply system.
The loads that are shed are -
D-A Sets Starting 48103 and 48106.
D-A Set Starting 48103.