Slow Speed Alternator

I am trying to source a slow speed alternator to suit a very low revving diesel engine (cruise at 600rpm)
Everything I have found to date needs to run at least at 3000rpm, which even with the smallest diameter belt wheel, I can't even get close to...
Any suggestions?

 

There are several options:
Increase the driver pulley diameter (the one on the engine). A 350mm diameter wheel will bring any alternator up to speed. If necessary you can go to a multi part arrangement with a jackshaft to get the ratio you need.

Have the alternator rewired to star, that will bring more volts at lower rpm.

Buy a really expensive alternator like this one, E-Series Models | Electrodyne | Brushless Automotive Alternators http://www.electrodyneinc.com/e-model.php?id=e350_12

 

What is the diameter at the engine?

 

Consult with Balmar, but this shouldn't be a big problem. You will want a large-frame alternator and probably need to run a multi-vee belt to use a small driven sheave. That probably means an accessory drive belt just for the alternator. And that allows you to get the belt speeds by hanging a bigger drive sheave just for the alternator. Using something like an L-series multi vee belt, you could use a 90 mm driven and a 280 mm drive pulley and should be in pretty good shape for any reasonable alternator. You might get away with J-series for a puny alternator.

 

I see that you're Down Under, so my idea might not be so good?
Anyway, the Leece-Neville company, (now owned by Powerline?,) made several series of alternators that were targeted for use on heavy equipment/fire trucks/police vehicles/school busses, in short, applications in which the engines spent a lot of time just at idle or a little above even when electrical loads were heavy.
Many of them would reach their rated output at ~1.5 > 1.8K RPM.
If you're forced into using a jackshaft, so be it, but in general they are miserable devices.

 

What diesel engine are you using?
Most modern mid range diesels idle at around 600rpm, but won’t like to be heavily loaded at that speed.
Look at the engines torque curve, and crunch some numbers before committing to this!

 

We had an old 900 rpm rated 343 cat with similar issues. The original low speed alternator was massive and expensive to replace. Darn think was about the size of a 3 gallon bucket. We eventually had an outfit cut us a large diameter pulley on an offset mount. It used the harmonic balancers bolts and fit around the damper. Allowed us to use a fairly big standard high rpm altenator. Was a little long on the belts but beat finding very expensive low rpm alternators.