Electric Vehicle VFD Application 1

[bill318]

Most EV conversions use a 9" 20HP (15KW) series wound DC motor. I would like to have regenerative braking using a 20-35HP(15-26KW)3-phase electric motor(0~3,000 RPM)run by a VFD. Seimens makes AC motor/drive combinations for EVs, but the cost is a bit high for my liking ($6-10K).

Are there any other commercial VFDs on the market that run from a DC power rail of 200V or less and have dynamic braking using an external load resistor bank?

The motor I would prefer to use would be a sealed, fan-cooled unit with dual out-put shafts.

What I would like to be able to do is: instead of using the resistive load bank, charge a bank of ultra-capacitors during high current braking instead. The on-board charger will then take the power from the capacitor bank and dump it back into the battery bank at a controlled rate.

I understand that most motors of this size use sensor feed-back, but was wondering if any have been developed for sensorless feed-back?

Any help would be appreciated, Bill

 

[jraef]

I just have to say that I have learned more about battery technology and what really works in this thread than I have in the last year farting around looking into it. Thanks everyone.

And I own a Prius (my wife drives it now because she drives more than me). I absolutely love it! It has an added benefit to me being an electrical guy. Mine came with a sticker (provide by Toyota with every car in 2001) that says "Eat My Voltage". I am one of the few I've seen who actually put it in my rear window. BTW, it does use NiMH batteries and an ultra cap. Mine is the older 288V, but I heard also that the 2003 and up use a 500V system. Here is a good link to thier FAQ if interested. It has a few other tidbits about safety protocols that Bill318 might be interested in. Click for link

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[itsmoked]

jraef why haven't you cracked open that trunk with the orange wires going into it yet?!?!

I'd be into mine in a week!

I rented one to let my Mom try for a day. (2005)

I was very impressed with the room inside, really surprised.

The price was hard to justify for her though. I did the analysis on it and using $5/gal which I expect gas to hit in the next 2 years her payback was still 18 years based on a Corolla and her annual miles.

So they actually do have a super cap in them.. I had no idea. You say "a" super cap. Is it one giant 2 lead device? Or just a figure of speech?

Maybe bill318 should be looking in a junk yard for a couple of them.

 

[jraef]

Figure of speech.

I have not cracked it open yet, because as soon as I turned it over to my wife she forgot to turn off the ignition switch one night (it makes no noise!) which ran the gas tank empty and drained the battery. That apparently killed some gas tank sensor which could not be replaced without replacing the entire gas tank, which could not be replaced without removing the entire battery system etc. etc. They tried to hit me up for $4,700, saying that in part, the damage was caused by my trying to jump-start it by attaching to the lead-acid battery in the trunk, which I assumed was just for the starter. I cried BS to that, and Toyota Corporate immediately backed off and forced the dealer to replace everything at no cost. Since then however, my wife will NOT let me near it with a screwdriver! You know how that is I'm sure, she makes a mistake, I get blamed for it.

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[LionelHutz]

Bill;

Most VFD's will allow about 15% undervoltage. It depends on the design and the programming. Some could go to >20% undervoltage. Most also allow at least 15% overvoltage, especially on the lower voltage models which are often 30%. With the example battery voltages you gave it would seem you're talking about a 35% voltage swing which seems like it would work OK. You might not use the full capability of the battery but could likely get close.

I just saw an add for Eurotherm showing a VFD that will operate on 110V AC, which would be about 150VDC. You could probably split the difference on charged vs discharged and run it on +15% or 170VDC charged and let it drop to -15% or 130V discharged without it giving you grief about your supply voltage. So, if that VFD has DC buss terminals then you'd good.

Note that we're still talking industrial VFD's here and you may still run into nuisance trips and other issues you wouldn't get with a traction specific VFD.

 

[cswilson]

I've been trying to find more data on Li-Ion batteries on-line. It's tough to find good apples-to-apples data, but it does appear that there have been some significant improvements in the current output capabilities of Li-Ion polymer (Li-po) batteries recently, although I still don't think they match NiMH batteries.

There also seem to have been recent improvements on the safety front, but again, I think they are still not as good as NiMH on this front.

 

[bill318]

A google search for “Common DC bus” AC drive yielded a few possibilities. Most of which had too high a DC bus voltage for my liking. A few are close, it is just going to take some more research or dumb luck to find them.

http://www.google.com/search?hl=en&lr=&q="common+dc+bus"+ac+drive&btnG=Search

This one was interesting...
Allen-Bradley Powerflex 700 series. 280-325VDC, 30HP+

http://www.ab.com/en/epub/catalogs/36265/1323285/1323309/tab6.html

-Bill-