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Charging Systems


Operation of AC8

from a BR training booklet

AC8 alternators generate alternating current which is then fed to the RUG unit. The rug unit consists of the diode assembly (silicon type) which rectifies the output.

The rug unit also consists of a second diode assembly making the alternator self excited and controlling the rotor circuit to control the output of the machine.

Replacement of AC8 Alternators and RUG rectifier / regulators

The CAV AV8 Alternator (both 50 Amp - BR Cat No. 15/58501, and 75 Amp - BR Cat No. 14/94221) and their associated RUG units were gradually phased out when more than minimum repair was required at Works.

RUG units that were considered repairable were modified at Works to help reduce maintenance and improve battery charging at engine idling.

The modification consisted of fitting a new diode assembly making the alternator self-excited (similar to the AC203). This eliminated the alternator field relay (energised via the train wires 33 and 34 and the drivers key switch (see wiring diagram below). Battery charging could then take place with the engines idling without the need for the drivers key to be 'ON'.

Additionally, the main rectifying diodes (Germanium type) were replaced by the more reliable Silicon type with the removal of the two protection relays, test button and indicator lamp.

The modification was covered in Engineering Instruction MD321 issued to BREL. All modified units were designated by the suffix 'A' as follows:-

  Type BR Cat No. Battery Type Voltage Setting
Original
Modified
RUG 11
RUG 11A
14/94904
15/11281
Lead Acid 29.5V
Original
Modified
RUG 14
RUG14A
14/98412
15/11285
Lead Acid 29.5V
Original
Modified
RUG 15
RUG 15A
14/94812
15/11286
NIFE 31.5V

Modified and un-modified RUG units are NOT INTERCHANGABLE

Either
a) For an unmodified unit - cables 33 and 34 to be connected up to terminals 1 and 2

Un-modified

Or
b) For a modified unit - cables 33 and 34 to be left disconnected and taped up.

Modified

FAILURE TO DO THIS WILL DAMAGE THE ALTERNATOR FIELD DIODES AND CABLES

Modified units are identified by the removal of the protection unit (including the test button and indicator lamp).

During modification, terminals 1 & 2 (between B+ and B- in the D.C. connection block) have been rewired to allow for toilet water heating to be installed on certain power cars at works overhaul. It is therefore not possible to interchange unmodified and modified RUG units.

The following connections are correct:-

Refurbished Class 101 DMC(L) vehicles with toilet water heating

These vehicles are identified by a heater water control panel mounted next to the RUG unit.

101 DMC

Note - only RUG 11A units must be fitted
Terminals 1 and 2 to be connected up. (A full description of toilet water heating is in W.R. Standing Order 2/H/104).

RUG 11
Inside RUG11

Inside a RUG 11 unit.

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