power bypass question

[phil b]

My 12 volt generator puts out more power than my batteries and rectifiers are able to handle during high winds. The rectifiers are inside during the winter for additional heat. They do get hot when I don't use a fan.

Is there must be a simple way to take the power from the three phase generator,

which has no neutral on the ground, and trigger the unit to bypass the power at a

specific voltage to an alternative load? I want to bypass the rectifiers and Xantrex C-40 units.

Also, I'm planning to convert my generators to a 48 volt system.

Hopefully, the bypass could be easily modified for higher voltage. Any ideas?

[Flux]

Phil

I am not quite sure which way you want to go. The easy way is to take power before the rectifier rather than rectify it and dump it, in other words make an ac diversion controller.

From your wording I am not sure that you don't want to change over entirely to an ac load and disconnect the rectifier. This would need a lot more thought so that you didn't end up with something hunting between the ac and dc loads.

For the first case it is easy but your ac load will see a 3 phase variable frequency changing between a sine wave and a square wave depending on load. Heaters are virtually the only thing that would operate on this and you would need to keep them balanced and they will be awkwardly low resistance. I would be tempted to switch in a first stage from a temperature sensor on the rectifier to reduce the dc charging current to something the rectifier can handle comfortably, then use a voltage sensor to connect a second stage to bleed off more power when your batteries are close to the dc control voltage setting and perhaps let a small residual charge be handled by the dc charge control in the normal way.

For the second system, you would need a complete ac load control that could operate independent of the batteries. This would give your more ac power if you did it right but it is a project in its own right. The waveform would stay a sine wave but would still be wild ac and I think you could only use it for heating without a lot of bother. You would have to give serious thought about how you implement the change from dc to ac load.

Flux

[phil b]

Thanks Flux,

 "I would be tempted to switch in a first stage from a temperature sensor on the rectifier to reduce the dc charging current to something the rectifier can handle comfortably, then use a voltage sensor to connect a second stage to bleed off more power when your batteries are close to the dc control voltage setting and perhaps let a small residual charge be handled by the dc charge control in the normal way."

This is exactly what I'd like to do. How would you accomplish this?

[phil b]

I just realized I didn't give enough info. 2 generators are producing 20 volts to a 12 battery system and 150 amps. The generators are really putting out too much power for the tiny system. That's part of the upgrade to a 48 volt system in progress.

Thanks for your consideration.

Phil