Some useful info on Alternator operation and construction.
Not exactly the same as R75 but a good guide.
The Rover 75 CDTi uses a three wire Alternator.
Heavy Duty wire (battery charging) is bolted to the Alternator, then connects to the Starter and onto to the Battery +ve (the heavy wire)
The other two connections in the small plastic plug...
One is the Field/ Excitation connection from Ignition on switch via a fuse.
The other is connected to the ECU, this is the one that operates the Charge Light on the dash.
http://homepage.ntlworld.com/william...aker1/alt2.htm