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#1
01-25-2010, 03:32 PM
 meanderingthemaze Senior Member Join Date: Jan 2010 Location: Los Angeles, CA Posts: 246
Mythbusters: Higher voltage motor = more powerful motor

I guess this question is part theoretical, part practical. Can anyone explain what the limiting factor is in the power any given motor can produce?

Looking at the basic P=IR statement, I suppose with the same current flowing, higher voltage would produce more power.

But then there's the practical side. How much power can you get out of a certain voltage on a motor? And what would be the design considerations to maximize power in a motor at a fixed voltage?

The reason this question came up is that I'm doing an pickup AC conversion and so there are only so many options out there. Azure Dynamics small AC motor ~156V is not powerful enough (I hear), so most people would recommend the higher ~320V motor. Recently I just heard about High Performance Golf Carts who makes a 96V AC motor that is more powerful than AD's ~156V motor. And it's much cheaper!

So can anyone help me understand this? This is probably just Electric Motor 101.
#2
01-25-2010, 04:23 PM
 Georgia Tech Senior Member Join Date: Dec 2008 Posts: 406
Re: Mythbusters: Higher voltage motor = more powerful motor

Quote:
 Originally Posted by meanderingthemaze I guess this question is part theoretical, part practical. Can anyone explain what the limiting factor is in the power any given motor can produce?
Well the biggest thing is the the amount of power you supply it! Namely the batteries and the controller...yes the Motor DOES have I^2 R losses that play but they are not as much a factor as the first 2.

Quote:
 Originally Posted by meanderingthemaze Looking at the basic P=IR statement, I suppose with the same current flowing, higher voltage would produce more power.
No it is I squared R that equals power but that is really Heat related loss. Power in the motor is really (Voltage * amps) - I^2 R
Quote:
 Originally Posted by meanderingthemaze But then there's the practical side. How much power can you get out of a certain voltage on a motor? And what would be the design considerations to maximize power in a motor at a fixed voltage?
Well the highest Brushed motor is about 350 volts and that a motor sepcially built to go this high...Like it having interpoles. High current motors Have big Brushes wires and Coils with Thick wires.
There is alot that goes into having a high perfomance motor...Do you want a High RPM motor? High Torque?
Quote:
 Originally Posted by meanderingthemaze The reason this question came up is that I'm doing an pickup AC conversion and so there are only so many options out there. Azure Dynamics small AC motor ~156V is not powerful enough (I hear), so most people would recommend the higher ~320V motor. Recently I just heard about High Performance Golf Carts who makes a 96V AC motor that is more powerful than AD's ~156V motor. And it's much cheaper! So can anyone help me understand this? This is probably just Electric Motor 101.
The basic rules apply for AC motors also, but there might be other details that are specific to AC motors...for one AC motors RPM is not totaly based on voltage alone but Phase frequency as well....any way if the AC 96 volt motor SYSTM has more power than It pull more current..

Last edited by Georgia Tech; 01-25-2010 at 04:25 PM.
#3
01-25-2010, 05:16 PM
 meanderingthemaze Senior Member Join Date: Jan 2010 Location: Los Angeles, CA Posts: 246
Re: Mythbusters: Higher voltage motor = more powerful motor

D'oh

I meant to say P = I*V. Don't know where my brain was.

So, I guess my major question is whether the operating voltage of an (AC) motor necessarily correlates to the max practical power of the motor. (By power I mean the ability to do more work, where more power means you can do more work, heavier lifting, faster acceleration, better climbing speeds, etc.)

Or is it just a coincidence that most higher power motors are also higher voltage?

Is my question too general or broad to have a specific answer?

This seems like the very first question one must consider when planning a conversion. What power requirements must I have to get 0-60 in 10 secs, or climb those big hills on my street, or just to keep up with traffic in a metropolitan city, etc. But everywhere you look you see conjecture and projecture(I think I made that one up). It's hard to get a straight answer. Of course once I do the conversion I can share the empirical data on my application, but it's a lot of money to gamble on. Do you just trust the HP charts of the manufacturer?

If so, how much HP would you need to move a 3000lb vehicle at 70mph, and to accelerate 0-60 in 10secs, or climb a 10% grade.

#4
01-25-2010, 06:08 PM
 gor Senior Member Join Date: Nov 2009 Posts: 416
Re: Mythbusters: Higher voltage motor = more powerful motor

Quote:
 Originally Posted by meanderingthemaze D'oh .... If so, how much HP would you need to move a 3000lb vehicle at 70mph, and to accelerate 0-60 in 10secs, or climb a 10% grade. Thanks for the reply.
you can do some exercising and find it out:
http://buggies.builtforfun.co.uk/Cal...-imperial.html

or make a bit of search and find answers on most of your Qs
#5
01-25-2010, 06:14 PM
 rmay635703 Senior Member Join Date: Oct 2008 Location: somewhere in wisconsin Posts: 555
Re: Mythbusters: Higher voltage motor = more powerful motor

Quote:
 Originally Posted by meanderingthemaze I guess this question is part theoretical, part practical. Can anyone explain what the limiting factor is in the power any given motor can produce? So can anyone help me understand this? This is probably just Electric Motor 101.
Generally voltage aside the amount of power a motor can generate is mainly dependant on its weight, more copper = bigger heatsync.

It is possible to have a very small motor generate a high level of power but the smaller it is the less time it will do so before damage.

In other words watts give power the bigger the motor and the more cooling you can get the more watts you can dissapate. That is why my little 6 3/4" can technically operate at 96v and drive my mini van to 65mph but it also fails if driven this way for more than a brief period of time.

Quote:
 Originally Posted by meanderingthemaze If so, how much HP would you need to move a 3000lb vehicle at 70mph, and to accelerate 0-60 in 10secs, or climb a 10% grade.
Quite a bit, it is generally acceptable and actually more economical to allow the vehicle to slow a bit on inclines (even if you have the power), also a 3000lb vehicle if aerodynamic only requires about 10hp on flat ground to go 70mph (think boattail) but if not aerodynamic this number can jump exponentially at 70mph.

In other words WHAT SPECIFIC vehicle are we talking? A s10 pickup, a car, a mini van?
#6
01-25-2010, 09:20 PM
 meanderingthemaze Senior Member Join Date: Jan 2010 Location: Los Angeles, CA Posts: 246
Re: Mythbusters: Higher voltage motor = more powerful motor

Quote:
 Originally Posted by rmay635703 Generally voltage aside the amount of power a motor can generate is mainly dependant on its weight, more copper = bigger heatsync. It is possible to have a very small motor generate a high level of power but the smaller it is the less time it will do so before damage.
OK, so this is very helpful in understanding the design consideration.

Quote:
 In other words watts give power the bigger the motor and the more cooling you can get the more watts you can dissapate. That is why my little 6 3/4" can technically operate at 96v and drive my mini van to 65mph but it also fails if driven this way for more than a brief period of time.
So, even if I find a motor that is capable of doing what I want, it doesn't mean it will hold up to the test of endurance of normal use.

Quote:
 In other words WHAT SPECIFIC vehicle are we talking? A s10 pickup, a car, a mini van?
1969 Datsun pickup L521, ~2150 lbs curb weight
#7
01-25-2010, 09:43 PM
 rmay635703 Senior Member Join Date: Oct 2008 Location: somewhere in wisconsin Posts: 555
Re: Mythbusters: Higher voltage motor = more powerful motor

Quote:
 Originally Posted by meanderingthemaze So, even if I find a motor that is capable of doing what I want, it doesn't mean it will hold up to the test of endurance of normal use.
Oh it will just make sure you get a large enough motor, I would estimate a good 10" or 11" forklift motor could probably do it for your little truck, its much better not to drive 70mph though. My motor is about as small as they come and it will drive my mini van up to 65 at 96v but it falls apart because its simply too small and overheats, the key is to keep your motor within its rated power output, once you find a decently sized motor, get the model and brand and post it here and the wise veterans will tell you its capabilities. Your truck is fairly small so you should be golden without burning your motor.

Quote:
 Originally Posted by meanderingthemaze 1969 Datsun pickup L521, ~2150 lbs curb weight
[/quote]
That is one of the better pickups to convert to electric, lighter is always better in electric. Is that pickup about 4 feet wide or so? If so it may be moderately aerodynamic as pickups go due to low frontal area, might consider lowering it a tad to gain better aero a good site to look at on that front is ecomodder.com. Also a front air dam, belly pan and maybe an aerocap would help matters more.

Many of the electric folks will convert something and forget that you can gain a lot of range and speed by overinflating tires and improving aerodynamics.

Good Luck there are many here who know much much more than I, but I would say that is an excellent choice for an EV pickup!
#8
01-25-2010, 10:08 PM
 meanderingthemaze Senior Member Join Date: Jan 2010 Location: Los Angeles, CA Posts: 246
Re: Mythbusters: Higher voltage motor = more powerful motor

Well, I really appreciate the info and help.

I did a little homework before choosing that car, but it's obviously not as aerodynamic as the Tesla. But pickup seemed like the easier conversion, since this is my first.

I don't have the link for the motor I'm looking at but some other people on the forum have used this companies' motors. They just came out with a new one that's 50HP, at 96V.

I'll post when I get back to my home computer.

Thanks.

EDIT: I just found a link. I believe this is the same motor. But this isn't the link for the manufacturer's site, this is a vendor. Scroll down to the end and look for the AC-50 motor/controller combo.
http://www.thunderstruck-ev.com/AC_d...erformance.htm

Last edited by meanderingthemaze; 01-25-2010 at 10:12 PM. Reason: found link
#9
01-26-2010, 04:36 PM
 meanderingthemaze Senior Member Join Date: Jan 2010 Location: Los Angeles, CA Posts: 246
Re: Mythbusters: Higher voltage motor = more powerful motor

OK, so here is the link to the manufacturer's site, and it appears it is the same motor as the above thunderstruck link.
http://hpevs.com/drive-systems/ac-50

Looks like they may have developed this motor specifically for my type of application.

Any opinions?

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 Tags ac motor, power, voltage

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