I am restoring a fairly old alternator, single phase, 4 poles, 230V, 8kVA, cos phi=0.8, 50Hz @ 1500 RPM.
I measured a couple of resistance values and I am wondering whether the alternator is healthy (Please see the pictures):
Slip ring No. 1 to 4 resistance (Ohms):
1-2: 3.2 1-3: 3.2 1-4: 1.8 2-3: 3.2 2-4: 1.8 3-4: 1.8
None of the slip rings is shortened to ground. Electricity is delivered from the armature via slip ring coals to terminals.
There are four stator windings A - D. Every stator winding pack is connected to an adjacent stator winding pack. Stator winding pack A and stator winding pack D both have their terminals leading outside to a small connector block at the side. Based on the corrosion of these terminals is seems as there has never been anything connected to these terminals.
Resistance between the cables leading to these terminals from stator A and D is 8 Ohm. No shorting to ground. Couldn't measure individual stator packs resistance as all wires are isolated and I didn't want to remove the isolation).
Based on these characteristics:
- Is the alternator healthy?
- How do I have to connect the leads from the slip rings to get L1 and N?
- What is the auxiliary stator connector block used for? (Assumption: excitation via 12V battery when alternator has no remanence?)