DIY Electric Car Forums> EV Conversions and Builds> Electric Motors

 NuWiki Register Blogs FAQ Members List Social Groups Calendar Search Today's Posts Mark Forums Read

#21
06-15-2012, 10:13 AM
 adeyo Senior Member Join Date: Jun 2012 Posts: 130

I assume this is a DC motor. But can somebody explain if this would be a good motor for my first run? 24 V but it says 578 hp! Is this accurate?

24V 2000rpm 26amp 578 hp
Attached Images

Last edited by adeyo; 06-15-2012 at 10:16 AM.
#22
06-15-2012, 10:27 AM
 major Senior Member Join Date: Apr 2008 Location: Ohio, USA Posts: 5,192
Re: 3 phase 15 hp ac.motor work?

Quote:
 Originally Posted by adeyo I assume this is a DC motor. But can somebody explain if this would be a good motor for my first run? 24 V but it says 578 hp! Is this accurate? 24V 2000rpm 26amp 578 hp

Do the math. 24V times 26A = 624 Watts. One hp = 745W. Maybe it is 0.578hp.

What you're looking at is a PM DC motor likely used for power steering pump. You obviously saw my post http://www.diyelectriccar.com/forums...91&postcount=2 I suggest you follow that advice.

Regards,

major
#23
06-15-2012, 11:02 AM
 adeyo Senior Member Join Date: Jun 2012 Posts: 130

Lol. ...i learned something new. I'm glad you think my name is ade ....that way nobody knows who i really an when i make those kind of mistakes
#24
06-15-2012, 03:43 PM
 PStechPaul Senior Member Join Date: May 2012 Location: Cockeysville, MD 21030 Posts: 1,182
Re: 3 phase 15 hp ac.motor work?

Quote:
 Originally Posted by adeyo I assume this is a DC motor. But can somebody explain if this would be a good motor for my first run? 24 V but it says 578 hp! Is this accurate? 24V 2000rpm 26amp 578 hp
No, that can't be. 24*26=624W. I think it is actually 5/8 HP, which is 469W, with an efficiency of 75%. This motor might work on a small tractor, or as an experimental load for a controller, or as a learning tool if you take it apart and see how it is constructed. But it would not be any better at moving a car than a starter motor.

Since you are still learning, you probably need to either have someone put together a kit for you, or start with basics and get some experience by trying a small EV build like a tractor or golf cart. And you should take some tutorials and do a lot of studying of basic electrical principles.

I have over 45 years experience and education in electronics and electrical power, and I still have much to learn about motors and controllers. Even before my formal education and industrial experience, I tinkered with electronics and mechanical contraptions.

Here is a friend operating a robot I made in 1960. And it has a motor and battery in it and the wheels make it go forward and reverse as selected by the hand-held control panel. I also built the shack in the background:

And this is me on a "racer" that some of us kids built. No motor, no brakes! We wore work boots and dragged our feet to stop! Later I built a racer out of steel, with an actual steering wheel and linkages to both front wheels. But I don't have any pictures. I gave it away to a friend and he said their father put a motor in it and made a go-cart but then he backed over it in the driveway and destroyed it. But I learned a lot build ing it, and many other projects, by the time I went to high school!

So, I know you are excited to dive into an EV conversion, but you really need some solid grasp of electrical fundamantals and some experience with smaller projects, if you really want to learn and not just have someone do it for you and hand over the keys so you're good to go!
#25
06-17-2012, 03:52 PM
 Dennis Senior Member Join Date: Feb 2008 Posts: 293
Re: 3 phase 15 hp ac.motor work?

PStechPaul, A larger pole count AC induction motor has no advantage over a lower pole count motor other than speed is reduced which means less gearing is required. A typical NEMA design B, 3600 RPM motor and a NEMA design B, 1800 RPM 3-phase motor of the same horsepower, will have identical performance; it is just that the torque of the the 1800 RPM 4-pole motor in this example would have double the torque.
#26
06-17-2012, 05:10 PM
 PStechPaul Senior Member Join Date: May 2012 Location: Cockeysville, MD 21030 Posts: 1,182
Re: 3 phase 15 hp ac.motor work?

Quote:
 Originally Posted by Dennis PStechPaul, A larger pole count AC induction motor has no advantage over a lower pole count motor other than speed is reduced which means less gearing is required. A typical NEMA design B, 3600 RPM motor and a NEMA design B, 1800 RPM 3-phase motor of the same horsepower, will have identical performance; it is just that the torque of the the 1800 RPM 4-pole motor in this example would have double the torque.
I have found that higher pole count motors of the same frame size have more torque but lower HP. I have three motors, each about the same size, and the 2 pole motor is 2HP, the 4 pole is 1.5HP, and the 8 pole is 1HP. But I think there is less difference for larger motors, such as 20HP and higher. I think this is because there are more slots in the stator and it can be wound more efficiently.

But my point is that, if you want to overclock a motor to get more HP, especially when replacing an existing ICE engine, you don't want to have a shaft speed much above 3600 RPM, which corresponds to a safe and reasonable cruising speed in all gears. Also, motor bearings and other construction aspects are designed for the rated RPM, but I think most bearings will work well up to 3600 RPM. So, you can overclock a 4 pole or 8 pole motor and get higher safe speeds and more HP, and keep the rated torque by following the V/F curve. And without actually rewinding a motor, the best you can do is rewire from star to delta so a 240/480 motor can be about 140/280. So with a 720V DC bus you can get 500 VAC which means you can get a 3.6x boost. A 4 pole motor would run at 6480 RPM, which is still within an ICE redline range, and probably safe. An 8 pole motor would run at 3240 RPM, which may be safe for continuous use. And also remember that you can get an additional 2-3 times rated torque for short bursts, so you might be able to get peak HP of 7x rating for a 3 phase induction motor. But don't count on it for more than a few seconds.
#27
06-17-2012, 10:03 PM
 Dennis Senior Member Join Date: Feb 2008 Posts: 293
Re: 3 phase 15 hp ac.motor work?

Quote:
 Originally Posted by PStechPaul But my point is that, if you want to overclock a motor to get more HP, especially when replacing an existing ICE engine, you don't want to have a shaft speed much above 3600 RPM, which corresponds to a safe and reasonable cruising speed in all gears. Also, motor bearings and other construction aspects are designed for the rated RPM, but I think most bearings will work well up to 3600 RPM. So, you can overclock a 4 pole or 8 pole motor and get higher safe speeds and more HP, and keep the rated torque by following the V/F curve. And without actually rewinding a motor, the best you can do is rewire from star to delta so a 240/480 motor can be about 140/280. So with a 720V DC bus you can get 500 VAC which means you can get a 3.6x boost. A 4 pole motor would run at 6480 RPM, which is still within an ICE redline range, and probably safe. An 8 pole motor would run at 3240 RPM, which may be safe for continuous use. And also remember that you can get an additional 2-3 times rated torque for short bursts, so you might be able to get peak HP of 7x rating for a 3 phase induction motor. But don't count on it for more than a few seconds.
Horsepower tracks closely with torque in AC induction motors that have breakdown torque in which you are referring when you say 2-3 times the full load torque. The speed variance is around 7% or less for a NEMA Design B motor from full load to overload to the maximum breakdown torque point. So the horsepower will also be about 2-3 times the full load HP rating since speed drop is very minimal.

In VFD applications we are told the safe motor speed limit is 5,000 RPM from various manufacturers of industrial 3-phase motors. I never seen any speed higher as a safe limit. Though I am sure it can be done.
#28
06-18-2012, 10:39 AM
 mizlplix Senior Member Join Date: May 2011 Location: The great American South/West desert. Posts: 1,316 Blog Entries: 4
Re: 3 phase 15 hp ac.motor work?

5000 RPM on my AC 50 motor is kind of scary sounding. 7000 RPM was just flat insane.
__________________
ivanbennett dot com/forum
AC Vehicle Propulsion Study Group

 Share or Bookmark this

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home General Forum     EV News     Chit Chat EV Conversions and Builds     All EV Conversions and Builds     Technical Discussion     Batteries and Charging     Controllers     Electric Motors     EV Performance     Electric Bikes     Non Road Going Vehicles DIY EV Wiki     EV Information     DIY Wiki Discussion Production EVs and Hybrids     Production EVs     Production Hybrids Marketplace     Classifieds     eBay EV-Related Auctions     Parts Vendors     Professional Conversion Services     EV Dealers EV Clubs     Dallas EV Club     TexomaEV.com     EVAoSD     NEAA     NZEVA     B-EVA     UtahEVInterest External Information     EVDL List

All times are GMT -6. The time now is 06:14 PM.