Best motor/control technology for and electric vehicle

Thread Starter

strantor

Joined Oct 3, 2010
6,782
Thanks shortbus. I believe I ran across that before but since forgot about it. I think I'll start browsing around there for ideas.
 

Smoke_Maker

Joined Sep 24, 2007
126
Shortbus

That is a great link to look at what all to consider before you start a EV project.

Stantor

Have you considered what you would like to start with, I wold like to try a BLDC system.
 

Thread Starter

strantor

Joined Oct 3, 2010
6,782
I really have a lot of reading to do before I settle on a "best" idea. I like the versatility of commonly available 3phase AC motors and drives like the ones linked to previously. I work with those every day and I know that if I could get a battery pack voltage high enough, I could make something work. The problems I'm seeing with that route is that I (*think*) I need a motor that spins 8000rpm or better and the commercially available motors that I am familiar with usually aren't available above 3450rpm. I could use a higher gear I guess, but even in 5th gear in my car, 3450RPM is about 75mph. I would like to retain all the functionality and performance of the ICE so limiting myself to 75mph is out of the question. Most of the DIY kit's I've seen cater to the DC crowd. I have seen this AC EV motor kit, which is the biggest one I can find and it's not even meant for cars; only e-bikes and atvs etc.

Basically my first-stage findings are that if I am going to deviate from the DC EV crowd, I am going to have to pioneer my own solution. BLDC sounds exciting but I've never seen one big enough. I could possibly rewind a 3 phase induction motor to double the speed, but I know that there's some engineering that goes into motor design and anything other than a direct replacement rewind job might not work.
 

Thread Starter

strantor

Joined Oct 3, 2010
6,782
for the past 8hrs I've been lurking on the DIY EV forum that was linked to. I created an account under the same name so I can see the pictures, but have not posted anything yet
 

Thread Starter

strantor

Joined Oct 3, 2010
6,782
The link to the 61KW motor took me to the metric mind homepage. I assume you are talking about the SIEMENS 1PV5135-WS24. That's a pretty dang sweet motor but that is an AC induction motor, not BLDC. it has a max RPM of 10,000 which should be good, but the price tag, ouch, 9,161$! Something like this is probably where I would start; 45kw is not enough, but if I can get 45kw for 750$, I should be able to get a 70KW or better for <2,000$ (my logic may be flawed) if I keep a close eye on ebay. Motors I am willing to buy used/refurbished.

your second link has too much infor for me to comment on right now. i need to browse through it.

NEDRA website looks fun I see 2 records for RX7 there, are either of them yours? I'm especially turned on by the white zombie, despite the fact it's DC
 

shortbus

Joined Sep 30, 2009
10,045
Strantor, are you sure about the RPM of your car at 75 MPH? That sounds kind of high for a cruising RPM. My 04 Grand Prix cruises at around 1800RPM at 65MPH. Heres a link to a RPM@MPH calculator; http://www.wallaceracing.com/gear-speed.php

I don't know about your use of a car, but around here its more stop and go than highway. A Hybrid EV I thought used the gas engine to supply the power to keep the electric drive system running. The electric motor is the drive force to the wheels, could be wrong though, often am. I personally don't think the use of both the gas and electric is doable by a DIY'er, but again thats just my opinion.
 

Thread Starter

strantor

Joined Oct 3, 2010
6,782
Strantor, are you sure about the RPM of your car at 75 MPH? That sounds kind of high for a cruising RPM. My 04 Grand Prix cruises at around 1800RPM at 65MPH. Heres a link to a RPM@MPH calculator; http://www.wallaceracing.com/gear-speed.php
according to this link, my 5th gear ratio is 0.815 and my differential ratio is 4.059.
my tire is a 205/60/15, so according to this calculator the diameter is 24.69" and given that info, the calculator you linked to returns this table:
Engine Speed (RPM) Speed (MPH)
8000 RPM 177.60 MPH
7500 RPM 166.50 MPH
7000 RPM 155.40 MPH
6500 RPM 144.30 MPH
6000 RPM 133.20 MPH
5500 RPM 122.10 MPH
5000 RPM 111.00 MPH
4500 RPM 99.90 MPH
4000 RPM 88.80 MPH
3500 RPM 77.70 MPH
3000 RPM 66.60 MPH
2500 RPM 55.50 MPH
2000 RPM 44.40 MPH
1500 RPM 33.30 MPH
1000 RPM 22.20 MPH

This is a 1994 celica and it has low gears. This is not the exact car I had in mind, but something similar, light weight, aerodynamic, etc
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
holy crap that's a top drive motor! I used to be a top drive technician, but never saw one of these
I was commissioning tech for Tesco top drives (hydraulic/electric) for a number of years. These motors from DRS where initially military implementations but Tesco made them successfull as top drives. These motors are internally liquid cooled, as are the inverters, which made them very dense power units. We stacked 3 motors for 1350HP top drives. Although these units are large, it's this type of technology that I'm convinced will lead the way in automotive drives. With 14 pole pairs, torque is maxed throughout the speed range. Double or triple that, then emply pole skipping over the horsepower range and one can reduce transmission requirement to 2 or 3 speed. That's up for discussion though, as a properly matched transmission system will model the current/voltage requirements for automotive needs. The automotive application is seeing alot of experimentation on the motor end, but the transmission, however it evolves, is of equal importance.
 

Smoke_Maker

Joined Sep 24, 2007
126
Something like this is probably where I would start;
700 Lb what are you going to build a tank :D

You are only going to strip out about 700 Lb of donor car and it takes 800 Lb of lead acid to equal 1 gallon of gasoline, a good way to size the motor is to take the HP of the gasoline motor and match it to a motor that can produce that HP for short periods of time and not overheat at the next stop/start.
 

Smoke_Maker

Joined Sep 24, 2007
126
Although these units are large, it's this type of technology that I'm convinced will lead the way in automotive drives. With 14 pole pairs, torque is maxed throughout the speed range.
I'm not so sure, you may be closer to this than I am, but when I visited the Allison transmission plant a couple of years ago where they make hybrid vehicles AC motor/ trans units the engineers were committed to 3 phase and I would be very interested in any leads anybody has that point otherwise.
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
I'm not so sure, you may be closer to this than I am, but when I visited the Allison transmission plant a couple of years ago where they make hybrid vehicles AC motor/ trans units the engineers were committed to 3 phase and I would be very interested in any leads anybody has that point otherwise.
We ran these with 3 phase inverters. Many years ago I worked on diesel electric locomotives that were DC traction motors. I don't see a reason to deviate from the 3 phase approach, for a number of reasons. The biggest being the availablity of proven technology at production costs. We must recognize however, the contribution that the automotive industry has made in advances on many basic designs. With that in mind, I'm sure that the multi phase motor is poised for redesign to service a specific application.
 

tom66

Joined May 9, 2009
2,595
Do most modern electric cars even require a gearbox? Power output is pretty good over all RPM ranges. The Nissan Leaf for example I believe has a single-reduction gearbox, with no user selectable gears. Reverse is handled by the AC inverter by swapping two phases, neutral disconnects phases and drive runs them normally forward. Plus there are re-gen modes which means the brakes are used far less often.
 

Smoke_Maker

Joined Sep 24, 2007
126
Do most modern electric cars even require a gearbox?
All the consumer EV's have only one finale drive gear that I know of because of the wide operating range of the motor, including the Extraterrestrial EV's.
 

Thread Starter

strantor

Joined Oct 3, 2010
6,782
Do most modern electric cars even require a gearbox? Power output is pretty good over all RPM ranges. The Nissan Leaf for example I believe has a single-reduction gearbox, with no user selectable gears. Reverse is handled by the AC inverter by swapping two phases, neutral disconnects phases and drive runs them normally forward. Plus there are re-gen modes which means the brakes are used far less often.
Thats what a number of peopke have said but personally I dont see how "decent/equal torque through the whole rpm range" equals "no need for a multispeed gearbox"
 
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