[Oeva-list] vfd's and ac

larry larry at energyventuresllc.com
Mon Oct 20 15:42:03 PDT 2008


For those interested in using VFD's on straight DC it's really not a big 
deal to bypass the rectifiers by going directly to either the brake buss 
or go to the capacitor buss
They are both on the DC side of the rectifiers
That eliminates the derating problem
Hitachi is real open and easy hookup
Allen Bradley on small units is bit of a pain
Yaskawa is another good one that's easy to work with
Just remember that if you are running a 240 or 480 VAC you need 240 or 
480 times 1.414 to get proper peak to peak voltages

I have several VFD's in the field running large AC irrigation pumps 
directly off of the PV
My largest is on a tree farm in Borrego California
It uses a 250 HP Allen Bradley and works fine if you program it correctly
It's 480 volts so I had to violate code a bit in going over 600vac open 
circuit but big deal.

As for AC motors I don't know why you would want to build your own with 
a VFD since Curtis makes a great inverter up to about 500 amps at 130 
volts such as the 1238
I buy my motors in lower voltage 180 frame from HiPerformanceGolfCars.com
Bill and Bryan custom wind a great motor and at $3200 for motor and 
inverter and instrumentation it's a bargain compared to using a VFD
The algorithims are not the same as a dedicated traction inverter
VFD's in an auto application are pretty funky
I did use them when building Air Conditioning units on my EV's but as a 
driver it's pretty bad

I now have a 1999 RAV4 PHEV with the AC drive just about ready to roll 
out the door
Just waiting on my LiFe batteries to arrive
Still has the gas motor and tranny but also will drive up to 20 miles on 
pure sunshine electrons



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