I'd had an idea to build a bench-testing setup for generators for a while (since childhood, actually - my grandfather had made a demo unit out of an electric motor, an Austin 7 generator, an ammeter and a lamp). Harv's request made it happen.
There was a three-phase motor sitting in the e-waste bin at work. It spun freely, and all three windings had the same DC resistance, so electrically and mechanically it was OK. One of the electricians at work kindly wired a "Jesus cord" to it, plugged it in and flicked the switch. It went, and made me wonder why it was in the bin.
There's the source of motive power. But (1) - it's a three-phase motor. I only have single-phase power at home. But (2) - it's an induction motor. It's not variable-speed. But (3) - it's a four-pole machine: 1500 rpm at no load. Fortunately, Altronics sells a variable-speed controller kit for induction motors. Single-phase mains goes in, variable-frequency three-phase power comes out. That's the first two problems dealt with. (3) can be overcome by making the drive pulley about twice the size of the Holden crankshaft pulley, so that I can run the generators at a speed equivalent to about 60 mph, which will be more than enough to get maximum output, should it be required.
I built the kit, and delta-connected the three-phase motor's windings as suggested. I needed a pulley with a groove deep enough to take both A and B section belts, because I'd be mucking around with both 6V and 12V generators. I discovered a piece of wooden kitchen benchtop, drilled a 3/4" hole in it, filed the keyway by hand, and drove it onto the motor's shaft. Now - how to true it up and cut the groove? I figured I would G-clamp the motor onto the bed of my father's wood lathe and turn the groove into the pulley. Much sawdust later, job done. I mounted the motor onto another piece of benchtop, which I drilled to take voltage regulators. A couple of generator mounting brackets and some 8 mm dia rod, cut to length and tapped 5/16" UNF, with 8 mm ID aluminium tube cut to size, allowed me to mount the generators. I attached the top generator bracket to the motor via some angle.
With this setup I was able to test generators and adjust regulators; but providing a suitable load was difficult - a hand-held 12V 50W halogen lamp was about the best I could do easily; and for 6V systems it didn't draw anywhere near enough current. Something better is needed.
So what I want is a constant-current, switchable load. Constant current? That's so that it'll pull the same current with a 6V generator as with a 12V one. With loads of 1, 2, 2, 5, 10 and 20 amps I can set any current from zero to 40 A in 1 A steps, and I don't need an ammeter. Whereas in your old-school lamp bank or resistive load, the current isn't in nice multiples of amps, so an ammeter is required. And the poor switches have to handle the full load current. There are better ways of doing things . . .
Rob
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Might have to get your help at some stage please to understand this thing better. If you would like to run it alongside your test bench you are more than welcome.