Diode value?

Three phase regulator from a KZ750H3. When making a very simple shunt regulator using a single zener diode from a rectifier output to ground (much like the old British bikes had), what value should the zener have (volts? amps? watts?)?

Thanks!

polkat wrote:

Three phase regulator from a KZ750H3. When making a very simple shunt regulator using a single zener diode from a rectifier output to ground (much like the old British bikes had), what value should the zener have (volts? amps? watts?)?

Thanks!

Bare minimum is:
14v
20 amps
280 watts

It should last a few hours then will fail and burn out everything on the bike.

A zener is made to be a detection device, not the actual high-power handling device. The old British regulators look cool, but that's about it. many run modern regulators but retain the zener and heatsink for looks (unconnected).

It is much more efficient to use a shunting regulator before the rectifier, than to use a clipping regulator after the rectifier.

Okay, although they are in every shunt regulator and see the same voltages, so I'm not sure why it would fail.

Anyway, I just can't afford (unemployed) a new replacement price (when new ones can be found) and the three R/R's (they were all SH230-12, but the '82 KZ750-4 uses a SH530-12) I've gotten off Ebay were all bad when I got them.

What would be a good (yet cheaper) altenative? I was considering the zener as it's super cheap.

You can try a reg/rec off a more modern bike as they would at least be newer. You just have to be sure it's the same config. as yours.

I think yours is 3-phase and made for a permanent magnet alternator, but you should confirm that.

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If you find that particular Zener, i don't think you'll find it's cheap.

Most Zeners you find are 1/2watt or 1 watt. A 14v, 1 watt zener will handle all of 0.07 A before it blows up. I suppose you could buy 285 of them and put them in parallel, but because they will all have slightly different voltage curves, they will have a chance of burning out one at a time which will avalanche into a big puff of smoke.

Alright, you've convinced me to drop the zener idea.

Yes, the R/R is for three phase. It originally used a Shindengen SH530-12. I haven't found one in new old stock anywhere, and the used one's from Ebay are usually junk.

Can anyone suggest a newer model that I can adapt?

polkat wrote:

Alright, you've convinced me to drop the zener idea.

Yes, the R/R is for three phase. It originally used a Shindengen SH530-12. I haven't found one in new old stock anywhere, and the used one's from Ebay are usually junk.

Can anyone suggest a newer model that I can adapt?

I don't have one off the top of my head, but if you search wiring diagrams, you just check for one where the alternator only has 3 wires coming out (usually the same color) and they go to a reg rec with 5 or 6 wires.

See what's on ebay, if the reg/rec has 5 or 6 wires where three are the same color, then check for a diagram on that model.

If you find any, send a link and I'll look at it.

Try to find wiring for ZRX's, ZX's, and maybe some Suzukis as well. I usually stay away from Honda and Yamaha electrics.

Thanks loudhvx, I know how it works and what to look for. Was just wondering if anyone knew offhand of similar regs. I'll start looking today.