3 phase induction motor as DC charger

[Tom Reed]

Ok, so I'm looking for an efficient way to utilize a 6/1 prime mover to direct charge a 48v battery bank. So another idea I've been entertaining is acquiring a 7-10 hp 3ph induction motor rated for 1725 rpm. Use the existing pulley from the ST-5 to belt it to the 6/1 and turn the motor 1800 rpm. Then add capacitors to one leg and adjust until output is around 100 vac. Feed the output into a 3ph bridge and take the output from the bridge into an MX60.

This config would also allow a quick change back to the ST-5 in the event of an inverter failure. I like redundancy.

Comments?

[mike90045]

I guess it should work, as long as you chose the right motor.  The wrong ones don't generate.  I think that's covered on some of the conversion sites.

[Lloyd]

I have read, a couple of times that peps are taking the output from from an automotive alt, direct to mx80 and it works, it even works with the mppt controllers as long as you can turn off the mmpt. As when the controller sweeps for the mmpt, it cause the engine/alternator to drop the load causing an over rev.

Lloyd

[Tom Reed]

It must not be an automotive alt with the avalanche diodes that clamp @ 30v.

[mbryner]

When I'm charging w/ MX80 it's always in MPPT mode.   It sweeps every little while.   You can hear the listeroid spin a little faster and then slow down as it builds up load again.  Doesn't really overrev.

[mobile_bob]

the only problem i could see with using an induction motor turned induction generator, feeding an mx60 or 80
would be during load dump. 

when the mppt samples the engine will speed up to its full governed speed or overshoot a bit which might cause an overvoltage
spike to the mx60/80

therefore if the mx60/80 has a upper voltage limit of 140vdc, i would set my induction generator to produce maybe 110volts max, so that
if and when it goes into load dump and speeds up the resulting voltage doesn't get higher than 140volts

i might also be tempted in using one of those varistors (sp) that clamps the voltage spike to help keep the voltage under what the max input
of the mx60/80 can handle.  (i think it is a varistor that does this, although i might be wrong and someone will correct me)

bob g

[Tom Reed]

Ok it looks like I'll make a full court press to make this happen.

Any comments on this bridge for the planned application?

http://www.mouser.com/ProductDetail/Ixys/VUO50-12NO3/?qs=sGAEpiMZZMuCl5o%252b%2fAuPoBTpCrezwdFeUjUWSt8MgpA%3d

[mike90045]

Ok it looks like I'll make a full court press to make this happen.

Any comments on this bridge for the planned application?

http://www.mouser.com/ProductDetail/Ixys/VUO50-12NO3/?qs=sGAEpiMZZMuCl5o%252b%2fAuPoBTpCrezwdFeUjUWSt8MgpA%3d

Just 58A cont, at 85C ?
http://ixapps.ixys.com/DataSheet/VUO50.pdf   has great PEAK amp specs, but the repetitive amps is low.  But better that stuff off ebay.   Mouser is out of stock, what's the lead time ?

[Tom Reed]

Didn't notice that there is a 16 week lead time. Guess I'll look else where.

[gregger2k]

Something like this shroud fit the bill.... http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2070379_-1
Overkill but safe.

[gregger2k]

Or a whole lot cheaper:  http://gb.suntekstore.com/3-Phase-Diode-Bridge-Rectifier-100A-1200V-SQL100A.html?&utm_source=gbus&utm_campaign=gbus

[Tom Reed]

Thanks Greg! Item from Suntek is now on order. Robin may have a motor for me. So things are underway.

[veggie]

Hey Tom,

any update on this project ?

veggie

[Tom Reed]

Yes! A 2$ spring on the governor resolved most of the issues with the functioning of the current system. So this work around is not needed. A frequency meter and 2 volt meters were added to the system and that gave me the info needed about the lazy governor. Now that that is fixed the voltage is stable enough that the AVR does not need to be installed either. I do like to keep things simple. Being off-grid the attraction to me is that if the magic smoke comes out of the inverters, the generator can run the place with the flip of a couple of breakers.

[Dualfuel]

Dear Tom,
Before I had generators...I simply routed legs from the three phase induction motor into the fuse box and ran the house directly. I had a fluke meter to set the engine governor to the right hertz, then arranged the capacitors to make the correct voltage. It was a limited but reliable system that cost $15 with no electronics.
I still have some 10hp GEs (oldsters with grease boxes) tucked away, for the "ya never know" times.
Nowadays, I would try the kill-a-watt meter to set the hertz and caps.
BPJ