PIPE DREAM Electric car using VFD and 3 phase motors

leitmotif

Member
Join Date
Nov 2004
Location
Seattle Wa. USA
Posts
3,680
Have one of those pipe dream projects of building / modifying existing chassis to make electric car.

Now that I have seen and am learning about PLC and VFD I want to use both in the design.

Conceptual design / perfomance criteria
RANGE 20 to 30 miles round trip.
TOP SPEED 60 mph
AVERAGE SPEED for range 45 mph

Longer trips will incorporate a trailer mounted battery for extra capacity or a diesel generator.

Want to use off shelf components
Want to use prepackged forklift type battery. I think these are typically 48 volt.

Want to use 4 individual motors - one on each wheel - this will give me 4 wheel drive. 4 motors will
eliminate transmission differential thus weight (may still need a gear reduction I know)
also give me redundancy, should lower motor size (and in theory total motor weight).
Also part of dream is to rotate motor/spindle/wheel and all to a 90 degree angle so parallel parking is done at 90 degree to curb no bakcing and filling -- to get in the slot just go sideways.

Now where can I get a VFD that will connect direct to battery? I understand forklifts have this in design stage.

I know I can do braking with a VFD BUT I want to do regenerative braking where I charge the battery. Not sure how to do this with a squirrel cage 3 phase motor. Wound rotor would work but a squirrel cage ??

Also where can I get water cooled motors? say in 5 to 10 HP range? I have little adipose tissue so I get cold in Seattle and I need LOTS of cab heat.

Any ideas thoughts suggestions???

Dan Bentler
 
My car uses a 208VDC Battery stack, followed by a voltage doubler to power the primary VFD. The main drive motor is 400/460 VAC 3phase.

Complicated, yes, but it does have the advantage of smaller wiring, and is more immune to a cell failure of a battery than low-voltage systems.
 
leitmotif said:
...Also part of dream is to rotate motor/spindle/wheel and all to a 90 degree angle so parallel parking is done at 90 degree to curb no bakcing and filling -- to get in the slot just go sideways...

I get it! Your a woman.

🤷

Sorry!
 
I've been interested in electric drive since the late 50's/early 60's when I was in grade school. I have come to realize that my plywood helicopter would have never flown. but I think the Box Car, 4' x 4' x 8' high, with a B+S under the seat would have, well until it got going fast enough to blow over. Actually, I think the transmission was a great idea for an eight year old. I thought that pulleys (3 step) like in a drill press would work, with a loose belt on each. with a rod and roller for each to tighten down the belt for each "gear". Still waas in the planning stage when I got to eight grade.

Back To AC Drive...

Since I have work on Mining Trucks and Locomotives with AC and DC drive systems, I would have to say the DC is more practical and forgiving. With DC, rather that going into Dynamic retarding (resister grid like some elevators), it could be easily sent to charge the batteries. Perpetual motion not possibe, but almost obtainable if you live in the rockies. 30 miles downhill from Estes Park to the flatlands.

One of the sweetest little electric vehicals I've seen is a Fors Ranger pick up. Someone makes a DC motor that bolts up to the bellhousing or driveshaft. Light enough to work, but still heavy duty enough to be practical.

As far as 4wd, it has been tossed around a lot. As far as AC regenerative retarding, it was tried in Komatsu Dresser mining trucks (200-250 ton) shortly after I left in 92, but I don't think it ever went over.

DC shortfalls are excessively high current when starting out. The mining trucks burnt off a lot of drive cable terminals. No ever determined the cuase, but I suspect that it had to do with poor heat transfer and disipation. The would burn in two about 5" from the lugs. I have a Chicago area manufacturer that would put the 535mcm cable into a copper pipe, and "press" it into a lug, pierce bolt holes in it, the hot dip solder it so the strands were in and part of the lug. The prototypes worked great, but the manufacturer would never give me any firm prices, therefore I couldn't write a P.O. Bad economical move on their part. 250 trucks times 20-30 cables, all 535cm.....

AC drive is probably somewhat practical, but how efficient is the inverter and drive unit? "Modern" AC drive locomotives generate 3 phase, rectify it into DC, feed it into a GE or Siemens VFD drives, then to the traction motors. The newest AC drive units that worked on at Electo-Motive (GM EMD) had two drive units, one for the front 3 tractions motors, the other for the 3 rear ones. 4500-6000hp diesels powering the generator. The engine has idle, and 8 "RUN" speeds, depending on load vs speed wanted. "RUN 8" being wide out.

DC was much simpler.

Can't wait till you get it done, and post the pictures, Dan.

BTW, Mike, got any pictures or progress reports on the Cart, or Duaghters car???

regards.....casey
 
Casey
Re One of the sweetest little electric vehicals I've seen is a Fors Ranger pick up. Someone makes a DC motor that bolts up to the bellhousing or driveshaft. Light enough to work, but still heavy duty enough to be practical.

NEVER saw one so all I have is 3rd hand info. Somewhere I read the Ford truck was AC drive. It WAS a good rig, people who Ford loaned it too fought over giving it back. Reportedly they did a tree hugger thing when Ford wanted to scrap it. Ford sold some to the "owners".

GM had the same results from the same group of people.

Anyway the advocates say AC drive can be done some have parts for sale - supposedly Siemens, BUT Siemens says they cannot support this venture and in one case the website was updated eaarly 2001 and in the other the business is for sale. Long story short I listen to advocates and then go to other sources to get the facts and validate what they say.

Forklift outfit said that they expected AC drive in a year or so.

Here in Seattle I grew up with electric trolley buses. Great for the hills. Lousy in snow, they sit there and spin, when chained up they tended to tear up the chains. Torque is a good thing but not in snow.

It is a pipe dream at this stage. Not enough money to do it, and I am in no big rush - I need to learn more about VFD first - good thing I am taking classes - I have access to a toy box - I could build a scaled down version maybe. Right now I am still finishing project building a hypothetical drill press to learn analogs in outs (in outs of analog maybe). I am now somewhat forced to learn PID so I got a plateful of learning.

From what I have seen of VFDs it seems a perfect application.

Thanks for thoughts. DC is a great application for traction, the railroads used to use it, and are now on 3 phase. If it works for them it (in theory) should work for me. Problem is I want to use off the shelf components.

Dan
 

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