Electrical Equipment


1 of 6 articles on Deltic loco design engineering
by Ian Strange


The main generators on Deltics are conventional direct current machines. Each generator has 10 poles, with current supplied by the auxiliary generator, and controlled by the load regulator. A further 10 auxiliary poles are connected in series with the main generator output, to help keep the current flowing through the armature coils at all times. Talking of output, these machines are rated at 1090 kilo-watts (1461hp), or 89% of the engine's rated output (inevitably there is some loss of power in the generator).

The main generators also double as starter-motors. They have a separate set of windings for this purpose, which are connected across the battery when the starter button is depressed.

The auxiliary generators are also direct current, producing 110 volts to power the following: Main generator fields; battery charging; air-compressors; vacuum exhausters; fuel pumps; traction motor blowers; operating coils of relays and contactors.

The traction motors (6 of them) are 4 pole machines. Direction of loco travel is changed by reversing the motor field-winding connections. The strength of this field is also varied in steps automatically by connecting resistances in parallel with them, i.e. "field diversion".


Main Generators
Manufacturer English Electric
Type EE829/1A
No. of Poles 10
Weight 10799lbs (4898kg)
Output 1461hp (1090kW)
Max. Voltage 660
Max. Current 1650 (continuous)

Auxiliary Generators
Manufacturer English Electric
Type EE913/A
No. of Poles 4
Weight 1686lbs (765kg)
Output 51hp (38kW)
Voltage 110

Traction Motors
Manufacturer English Electric
Type EE538/A
No. of Poles 4
Weight 4987lbs (2262kg)
Rating 550 amps/660 volts
Axle/Motor Gear Ratio 53:18


Much of the switch-gear is comprised of relays and contactors. Relays are actuated electrically by solenoids. Electro-magnetic contactors are similar in principle to relays, but handle larger currents. Their contacts are designed to avoid damage by sparking when they open. Electro-pneumatic contactors handle the very large traction currents flowing through the motors and main generators. The pneumatic actuation enables the contacts to be held firmly closed under high pressure.

Most of the remaining switch-gear can be grouped under the headings of manual switches, circuit-breakers, and protection devices (for detecting low oil pressure, or low coolant level, etc.).

One other type of interest is the load regulator, as mentioned in the section on engines. This is effectively a variable resistor, varying in a series of small steps by the closing of contacts by a rotating arm. The arm is moved by an hydraulic vane-motor controlled by the governor, via the "regulator controller". The latter device sets the speed of the vane-motor. This system did not provide very fine control of power at low speeds and an experiment was carried out on a Deltic for electronic load-regulation. This employed a linear commutator to give fine variations of the main generator field at loco speeds up to 8mph. The idea was not adopted since Deltics would benefit little from the improvement, for the high speed passenger duties that they performed (ref. 1).


ETH was added to the Deltics during 1970/71 after experiments on D9007 from 1967. With no space to install a suitable generator, power had to be taken from the main generators. Rather awkward, since each main generator's output varies from 0 to 660 volts, while ETH requires something a little more constant. This was ingeniously achieved by taking ETH power from both main generators when the engines were idling. When the driver applied power, ETH supply switched over to just one main generator - the one nearest the driver. The controls were modified so that only that leading engine would rev up initially, with the rear engine catching up once full power was called for. This would allow the ETH voltage to build up more quickly, since this one engine would be revved up more during a standing start. Time delays built in, prevented too frequent switching of circuitry.


1) "Railway Engineering Journal" May 1972 (I. Mech. E.).


Sources of technical information:
English Electric maintenance manuals.
"Deltic Deadline" no.52 (Deltic Preservation Society) - article on ETH conversion by Ray Smith, C.Eng., M.I.Mech.E., former chairman of Deltic Service Problems Working Group.
Note that some books and articles quote data from the prototype Deltic by mistake.

Ian Strange

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