Rectifying 120VAC

[veggie]

What's the most efficient way to convert 1000 watts, 120VAC to 120 VDC ?
(I have a 1kw DC device which can accept 90V to 150V)

My 120VAC generator will be providing the AC power.

[keith71]

I have a 2000 watt 17.4 amp AC generator head..  It is 2 wire 120 volt only.. I bought a 200 amp single phase bridge rectifier. At 3600 generator rpm, it puts out 120 VDC. At 3000 rpm it is about 100 VDC.. I could probably lower the rpm more to get a 60 volt DC output. But have not tested yet.. I am hoping I am able to get 30-40 amps out of it.

Have not tested amps on the dc ouput yet as I have not hooked up a load and a shunt to measure yet.. I think it will be fine as far as dirty or clean output is concerned.  Will eventually feed one of the inputs on a solar charge controller, or the inverter itself on a utility input connection. Some people put a capacitor before the charge controller to smooth the dc output. Others have said most of the newer better inverters are not super picky withe the input.

That is as far as I have gotten so far.

[keith71]

Is your device solar in anyway?

[veggie]

Thanks Keith,

The idea is similar to yours. Feed 70 to 130 VDC into an inverter.
I suspect it may be best to add capacitance to the pulsed DC after rectification.
One benefit of this setup is that the generator is no longer bound to making perfect 60hz power.
RPM fluctuations either side of the target RPM are ok.
My 3600 rpm gen head does have a low voltage drop-out, so I think the minimum I can produce is about 95 volts.
However !! I do have a 3KW ST type head that may be able to produce AC power all the way down to 36 volts.

Does anyone here have experience running ST heads at low rpm for a rectified DC output ?



 

[Tom Reed]

Putting a load balancing transformer on my ST5 made it good enough to run the house and inverters on. 3 phase rectifies a lot cleaner than single. I'm still looking for a 3 phase induction motor to make a generator from. However since upgrading to LiFePo batteries the generator only needs to run about 40 hours per year.

[keith71]

Would this 5 hp 3 phase motor work better for rectifying 3 phase AC to single phase dc, provided you could keep the volts under 150 ?  Would it be more efficient and more powerfull than a 3 phase car or truck alternator?  Alot of the AIO inverters can take alot of DC input.. And I think there are some that will take straight AC voltage on an  AC input.  Just starting to educate myself on anything solar.. Obviously it is here to stay.. IMO, (which isnt much yet) it is the best way to go for electricity, heating cooling it does it all.. Add a nice dc generator and everything is covered..

Also so much cheaper than 5-10 years ago. Those lifepo4 batteries seem great.

Sorry for the blabbering rant veggie..

[Tom Reed]

Not many have done this, so the answers to your question are unknown. Getting brushes out of the system has to improve reliability. IIRC, a capacitor is put between 2 legs and it will self excite. Bigger bearings and totally enclosed have to help reliability too.