How to limit voltage output from 3-phase permanent magnet alternator.

Thread Starter


Joined Mar 3, 2020
So here's the issue... My new 2000w wind turbine is designed to produce 3-phase 96VAC, but my grid-tied controller is only designed for 3-phase 40-90VAC. I realize that voltage and rpm's are proportional, but due to the high winds we regularly experience, I'd expect the 90+ condition to happen too often. I had considered a voltage-controlled relay to switch from feeding the controller to shunting to a braking system (to keep the turbine from flying apart at excessive rpm's).

How can I build a 3-phase AC voltage regulator to prevent the voltage from exceeding 90VAC? If it was single phase, I'd just use a handy motor speed controller to trim the voltage and put a BIG fan on it. But, I don't even know where to start when it comes to 3-phase AC voltage regulation.

I have also considered a 3-phase step-down transformer (96VAC to 48VAC), but good luck finding such a unicorn. :)
Any advice would be greatly appreciated!


Joined Jan 23, 2018
One alternative will be to copy what the power companies do, and use an automated transformer tap changer. With just one tap per phase on the primary and one per phase on the secondary you can have a total of four possible ratios, either stepping down or stepping up.
OR, in place of that 96volt to 48 volt transformer, use a 240 to 120 volt transformer. THOSE are fairly common. Or, try a 480 volt to 240 volt transformer. And keep in mind that there is also a WYE/Delta change that produces significant voltage differences.
So there you have a number of suggestions that do not involve any electronics and are quite efficient. And rather reliable as well.
Also, if the individual phases are accessible on your alternator, just switching to the "WYE" connection scheme will give a lower output voltage.