Questions and answers on alternators that originally appeared in the Railcar Monthly Bulletin

Question: Our 108 has the following alternators  Type AC 203. These apparently have a cooling fan whereas the AC8 do not. Our 108 set also has the following voltage regulators, Type RUG 11A. I am told by one of the chaps he believes that the normal regulator for AC 203 is a type 460/C3. Our unit came out of service wearing the kit as mentioned and they want to know is this standard or was it a BR mod. Any information welcome.

(some details of the RUG11A are mentioned here)

John Joyce: The RUG11A is the box about a foot cubed, probably with a metal grille top and bottom? This was - in its original incarnation - the rectifier for a pair of AC8s, with 12 diodes (probably germanium) mounted inside the box, the grilles being for cooling. The (mechanical) regulators were mounted under a separate cover on one side secured by four screws. In some instances the regulators were replaced with solid-state ones in small aluminium cases.

I believe the RUG11 was later modified to suit AC203 alternators, the AC203 having ITS rectifier (but not regulator) in the alternator itself (hence the cooling fan). The 'innards' of the RUG11 were presumably wired out or removed altogether, leaving it to house the regulators and as a connection box. I've never had chance to dismember one of these.

Another system again, presumably where AC203s were fitted from new, has a smaller plastic box containing the small aluminium-cased solid state
regulator, current shunt and connections. This may be the 460/C3.

GFB: The AC203 comes in three variants  -  60A, 80A or 100A - and you need to have the correct regulator.   I buggered up 2 60A regulators on one of the buses when I unwittingly fitted an 80A alternator (or vice versa - I can;t remember).   The regulator should say on it what voltage it is for.

The solid state regulator is Type 440 but often incorporated in the complete control box which has a different number.

The plastic box you refer to is the control board, sounds like you have got a 460C-3. A normal Lucas part, not a BR concoction!!   The aluminium part on top is the regulator;  sounds like a 572-2 should do you?  (see numbers above).

Question: Does anyone know how to change the maximum voltage setting on the CAV 460C regulator? One of the books that covers generating equipment says

"The regulator is set for a maximum voltage of

29.5 Volts - Lead Acid batteries
31.5 Volts - NIFE batteries"

but does not say how to set it.

GFB: I don't think you can change the voltage setting - the Lucas catalogue lists several different control boards including the 460 type,  each for different voltages.   460C is now 460D and these control boards each contain either a 440 or 572 Regulator - the little square metal part that screws on top. The regulator appears to be for set voltages.  From the current Lucas catalogue:-

Cont Box Regulator Notes
460D-1 572-1 Standard
460D-3 572-2 For AC203 60A;  shunt calibrated only for 60A
460D-5 572-3 For AC203 80A;  shunt calibrated only for 80A
460D-6 572-1 For AC203 70A and 100A

All the above regulators available on their own too, also
572-5M Marine, waterproof cover
440D-24-9 Standard, encapsulated
440D-24-10 Military spec
572-4 Standard with warning light facility

It may be that you just need to get a new regulator for your control board. They aren't too expensive, about £25??

Other types of regulator I have come across, which all seem to be older versions of the above types, are 440A-24-2;  440-24-2  (both 60A); and 548-3
(80A).

Hopefully all these numbers may be of some use to you all.