Generating new donations
Generating new donations
A couple of weeks ago we went to see the loco's generators under repair at Bowers Electricals Ltd. Two generators form a part of the Power Unit, a main generator which provides a variable voltage from ~100vDC to 800vDC for the traction power and an auxiliary generator which provides a constant 110vDC for the auxiliaries.
As with everything we do there's a cost involved and the cost for the generators (whilst representing best-value to us) is not insignificant. Add to this the impending cost of the cable to come and you can sense a fund-raising effort upcoming! The front page and D5910 Lottery page have all the details you need, please click the link to have a look at the proposal.
The photo below shows the main generator carcase (behind), the brush ring and the end cover. The carcase is the main frame of the generator and inside it are the poles (or field-windings) and interpoles which (partly) control the output of the generator. From school-level physics; a generator is a number of loops of wire which rotate inside a magnetic field, this action induces a current to flow in the wire and this can be collected by connecting the wire to a load. The output of a generator can be increased by increasing the field strength, increasing the rotational speed of the loops of wire, or both.
The auxiliary generator is mounted on top of the main and the attachment points can be seen on the carcase below.
The generators look to be in fairly good condition, this is because when we rebuild the engine 15 years ago we also did the generators, their trip to Bowers is to do the stuff which we couldn't do at the time. Both machines will get a full clean and varnish, new bearings, brush box overhaul, cable renewal, insulation and continuity test. They'll also get a trace-heat element installed so that we can keep the machines above the dew-point and stop them sweating.
The other major component of the main generator is the armature. This is the rotating part of the machine, you can see the flange at the back where it's connected to the output from the engine (phasing case), then working right to left; the windings, the commutator and the bearing face. The armature is surprisingly small in terms of diameter, this is because in its working condition its rotational speed is very high. Unlike a 25B (Class 55 loco) generator which is slowed down by the phasing gears to 1125 rpm at full power, this turns at engine speed - 1600rpm, that's fast for a DC machine and a small diameter keeps the surface speed down.
The auxiliary generator is virtually identical to the main, except that it's smaller. Showing its 'patina of use' appearance to good effect, the carcase is seen below with various component parts in a box in front and the brush ring to the fore.
The same repair specification will be applied to this machine, including the addition of the trace-heating.
The auxiliary generator armature and the front and read endplates below. Also visible on the right of the photo is the main generator carcase with the field coils (big) and interpoles (small) clearly visible.
