Changing an induction motor voltage

AC, DC, amps, volts and kilowatt. It's all discussed in here
User avatar
Johny
Senior Member
Posts: 3647
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Changing an induction motor voltage

Post by Johny » Wed, 15 Jul 2009, 01:33

I hope that was an unused toilet brush or that VFD may start producing dirty output.

Squiggles
Senior Member
Posts: 742
Joined: Wed, 22 Apr 2009, 03:19
Real Name: Neil
Location: Newcastle NSW

Changing an induction motor voltage

Post by Squiggles » Wed, 15 Jul 2009, 02:18

weber wrote:
woody wrote: Gah! You don't have a beard or braces! What kind of engineer are you?

Just be glad I spared ya the glare off me bald strip. Arrgh. Image


You know, I recently met Messrs Weber & Coulomb.
We three all turned out to be fiftyish, greyish, baldish, blindish and spoke fluent engineerish....scary really.

I suspect we all have very patient partners as well.

User avatar
weber
Site Admin
Posts: 2288
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Wed, 15 Jul 2009, 02:36

Squiggles wrote:You know, I recently met Messrs Weber & Coulomb.
We three all turned out to be fiftyish, greyish, baldish, blindish and spoke fluent engineerish....scary really.

I suspect we all have very patient partners as well.

Ah. You got that right too. Image

Mr Squiggles, you know, Coulomb and I hadn't fully understood that the rest of your family was waiting for you in a car, out of sight, until about when you were leaving, or we would have invited them all in for a cuppa. Please give them our apologies for that. It was good to meet you.

I hope ACMotor has a patient partner too. Otherwise I'll be in big trouble with her soon, when she finds her electronic kitchen scales underneath a motor in the shed. Image
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
acmotor
Senior Member
Posts: 3591
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Wed, 15 Jul 2009, 03:17

.... intercom crackles... Have you seen my kitchen scales ??

Ummm, no ,.......... but you can borrow my electronic torque meter.

Your what what ? .........Don't go bringing any of those greasy bits in from the shed.

Ok, dear, I won't. Image


weber, are you psychic too ? ... Ok , now , next weekend's lotto numbers....
Image
iMiEV MY12     99,820km in pure Electric and loving it !

User avatar
acmotor
Senior Member
Posts: 3591
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Wed, 15 Jul 2009, 23:37

If anyone in Perth is interested, I'm taking the little dyno along (to demo) to the AEVA meet at UWA tonight, 7:30pm. Image
iMiEV MY12     99,820km in pure Electric and loving it !

HeadsUp
Groupie
Posts: 235
Joined: Sat, 28 Feb 2009, 09:13
Real Name: Mark Whatley
Location: Sydney
MSN: alexandria63@hotmail.com

Changing an induction motor voltage

Post by HeadsUp » Tue, 03 Nov 2009, 11:13


What happened next Goldilocks ?

the thread just stopped ?


was it started again elswhere or did everybody fall into a worm hole ?


i was wondering what the x-12 motor did on a dyno........ Image


is this the point where you dropped the 0.37 kW motor in the bin and had the 11 kW Suzi motor rewound ?


or did you invent something patentable and decide to keep it all hush hush ?

?

?
Buddha...There are only two mistakes one can make along the path to truth - not going all the way and not starting

User avatar
woody
Senior Member
Posts: 1701
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

Changing an induction motor voltage

Post by woody » Tue, 03 Nov 2009, 16:03

HeadsUp wrote:
What happened next Goldilocks ?
I think "Silver Fox" is more accurate than "Goldilocks" :-)
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
acmotor
Senior Member
Posts: 3591
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Tue, 03 Nov 2009, 23:33

Perhaps grey.

Sorry HeadsUp, the next step was the 12 coil rewind of the red suzi 11kW in the red suzi thread picks up about here . Now I need a bigger controller and battery pack Image . I've still to test out star delta switching but a bigger controller would be more elegant.
iMiEV MY12     99,820km in pure Electric and loving it !

User avatar
Richo
Senior Member
Posts: 3082
Joined: Mon, 16 Jun 2008, 00:19
Real Name: Richard
Location: Perth, WA

Changing an induction motor voltage

Post by Richo » Tue, 03 Nov 2009, 23:40

HeadsUp wrote:
What happened next Goldilocks ?


A good time was had by all.
It was a late night.
Acmotor's tests also indicated near unit is near impossible Image

It did prove you can get a small motor to pack a serious punch.
Help prevent road rage - get outta my way! Blasphemy is a swear word. Magnetic North is a south Pole.

User avatar
acmotor
Senior Member
Posts: 3591
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Tue, 03 Nov 2009, 23:55

Say what ???
Image
iMiEV MY12     99,820km in pure Electric and loving it !

User avatar
Richo
Senior Member
Posts: 3082
Joined: Mon, 16 Jun 2008, 00:19
Real Name: Richard
Location: Perth, WA

Changing an induction motor voltage

Post by Richo » Wed, 04 Nov 2009, 00:22

You had two controllers and two motors.
The first controller turning the first motor using ~12kW.
The second controller was using regen from the second motor to power the first controller.
So the only power used was the loss of the system.
It was quite a good test.

I remember having a good time Image

Oh you mean the unity bit.
yes no laws of physics were broken that night.
No patents pending.
Help prevent road rage - get outta my way! Blasphemy is a swear word. Magnetic North is a south Pole.

User avatar
weber
Site Admin
Posts: 2288
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Wed, 04 Nov 2009, 00:58

Just in case anyone who cares missed it, there is a link to some excerpts from a classic text on induction motor winding, that confirms a lot of stuff in this thread and other stuff besides.



Originally posted here

forum_posts.asp?TID=1423&PID=18915#18915



But this thread may be more appropriate.
Last edited by weber on Tue, 09 Oct 2012, 10:41, edited 1 time in total.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
coulomb
Site Admin
Posts: 3060
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by coulomb » Tue, 02 Feb 2010, 03:34

A paper on the subject:

P. L. Chapman and P. T. Krein, “Motor re-rating for traction applications—
field weakening revisited
,” in Proceedings of the IEEE International Electric Machines and Drives Conference, 2003, pp. 1391–1398.

Lower quality but more official copy here: http://power.ece.uiuc.edu/chapman/paper ... 03%202.pdf

It seems we're not the first to figure out this stuff or apply it to electric vehicles. In case you're wondering but lazy, they claim that the efficiency with overvoltaging or "rerating" by 3.5x "is potentially higher" ("to first order") "in the re-rating case than in the nominal case".

Edit: original post: DIY electriccar.org forum "Pure horse power DC vs AC" post 272.
Last edited by coulomb on Mon, 01 Feb 2010, 16:38, edited 1 time in total.
Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

User avatar
acmotor
Senior Member
Posts: 3591
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Tue, 02 Feb 2010, 04:15

Image

Makes sense from my experiments. I guess I was lead by some to be looking for how much the efficiency suffered rather than by how much it may have improved.
It answers the lack of 'expected' temperature rise.
iMiEV MY12     99,820km in pure Electric and loving it !

User avatar
coulomb
Site Admin
Posts: 3060
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by coulomb » Tue, 02 Feb 2010, 04:48

acmotor wrote: It answers the lack of 'expected' temperature rise.

I still expect a marked temperature rise at "scaled full" output. If the efficiency rose from say 93% to 94% but the output power increases 3x, then 3x6% is still a lot more than 1x7%. A lot depends on the cooling, of course.
Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

User avatar
weber
Site Admin
Posts: 2288
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Tue, 02 Feb 2010, 05:16

acmotor wrote: Image

Makes sense from my experiments. I guess I was lead by some to be looking for how much the efficiency suffered rather than by how much it may have improved.
It answers the lack of 'expected' temperature rise.

Don't forget that the percentage efficiency may increase (and hence percentage losses decrease) even though the absolute losses increase. This is because the mechanical power output increases by a greater factor than the absolute losses increase. This is what I predicted would happen based on earlier readings.

Based on your experiments, my guess now is that the absolute losses went up a little (although nowhere near as much as I predicted), but the motor also got better at dissipating the heat due to the faster internal fans, or something ...
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
weber
Site Admin
Posts: 2288
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Tue, 02 Feb 2010, 14:56

Good though it is, the article completely fails to mention that you can get higher re-rating factors, without exceeding mechanical RPM limits, by using motors with more poles.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

Tritium_James
Senior Member
Posts: 683
Joined: Wed, 04 Mar 2009, 17:15
Real Name: James Kennedy
Contact:

Changing an induction motor voltage

Post by Tritium_James » Tue, 02 Feb 2010, 15:08

weber wrote: Good though it is, the article completely fails to mention that you can get higher re-rating factors, without exceeding mechanical RPM limits, by using motors with more poles.


Yes, but you'll have to over-rate your motor controller by even more, as the higher the frequency, the worse problems you're going to have with power factor. That can be overcome with more voltage, but that's at the expense of the efficiency loss of a controller rated to the higher voltage...
Last edited by Tritium_James on Tue, 02 Feb 2010, 04:09, edited 1 time in total.

User avatar
acmotor
Senior Member
Posts: 3591
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Wed, 03 Feb 2010, 05:54

"....by using motors with more poles."    Image Good point though.

TJ, You lost me there. Why more problem with power factor ?

Just looking at tables, a VFD for 690VAC is more efficient than one for 200VAC for the same kW since current is lower. But both >97% anyway.
iMiEV MY12     99,820km in pure Electric and loving it !

Tritium_James
Senior Member
Posts: 683
Joined: Wed, 04 Mar 2009, 17:15
Real Name: James Kennedy
Contact:

Changing an induction motor voltage

Post by Tritium_James » Wed, 03 Feb 2010, 23:00

The problem with power factor is that as you go to a higher frequency, the voltage required to get the current moving in the motor phases fast enough will go up (inductance is the same at any frequency to a close approximation). So to get the same kW out of a higher pole count motor, you'll need a higher kVA rating on the controller. Either that or work out how to drop the inductance down when you rewind it...

Of course, frequency has only gone up if you're spinning this higher pole count motor to the same rpm as the lower pole count type, but doing exactly that is kind of the point here...

So if you look at high power density induction machines at the moment, the ACP system is a good example. 4 pole motor @ 400Hz = 12000rpm. Since this is too high to make gearboxes easy, an 8 pole machine at 400Hz would probably be a better choice for a normal car.

antiscab
Senior Member
Posts: 2139
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Changing an induction motor voltage

Post by antiscab » Thu, 04 Feb 2010, 00:26

Tritium_James wrote: Either that or work out how to drop the inductance down when you rewind it...


i would have thought putting the poles in parrallel by doing a re-wire also drops the inductance aswell?

by the same token, by using fewer turns on each pole (of thicker wire) does that not result in reduced inductance aswell?

Matt
Matt
2008 Mazda 2 - EV Shop convert
2011 Blade Electron mk6
2007 vectrix - 117'000km
1993 Electrolux - needs batt and charger
1998 Prius - needs batt
1999 Prius - needs batt

Tritium_James
Senior Member
Posts: 683
Joined: Wed, 04 Mar 2009, 17:15
Real Name: James Kennedy
Contact:

Changing an induction motor voltage

Post by Tritium_James » Thu, 04 Feb 2010, 15:59

antiscab wrote:i would have thought putting the poles in parrallel by doing a re-wire also drops the inductance aswell?
You'll still have the same number of poles, so I don't think this changes anything.
antiscab wrote:by the same token, by using fewer turns on each pole (of thicker wire) does that not result in reduced inductance aswell?
This is the key point. Now I've thought about it further, I think the overspeed makes no difference to the power factor. Say you've rewound the motor for 4x less voltage, so you have 4x less turns, which means 16x less inductance. But then you spin it 4x faster, and it looks like the reactive current works out to exactly the same percentage as it was when you started. So apart from the increased iron losses, running these motors at a higher frequency really is almost something for nothing.

antiscab
Senior Member
Posts: 2139
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Changing an induction motor voltage

Post by antiscab » Fri, 05 Feb 2010, 11:55

Tritium_James wrote:
antiscab wrote:i would have thought putting the poles in parrallel by doing a re-wire also drops the inductance aswell?
You'll still have the same number of poles, so I don't think this changes anything.


the way i was thinking was:
4 poles, 1H each.
H = delta A per second per volt applied

in series = 4H, ie 4 volts for each amp change per second
in parrallel = (1/4)H, ie 1/4V for each amp change per second.

thats about as far as my understanding takes me.

the only time (in theory perhaps?) i would expect PF to get noticeably worse is when pushing for max torque.

Matt
Matt
2008 Mazda 2 - EV Shop convert
2011 Blade Electron mk6
2007 vectrix - 117'000km
1993 Electrolux - needs batt and charger
1998 Prius - needs batt
1999 Prius - needs batt

Nevilleh
Senior Member
Posts: 770
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Changing an induction motor voltage

Post by Nevilleh » Fri, 05 Feb 2010, 11:58

Voila! You have dunnyit!
Who'd have thought the ubiquitous toilet brush is the answer to free energy. Quick, take out a patent. Maybe you could sell it to these guys:
http://www.eagle-research.com/products/pfenergy.html

BTW, its Thermodynamics, not Thermalunderpants and the proper, scientific definitions of the 3 laws are actually:

1 You can't win, you can only break even.
2 You can only break even at absolute zero.
3 You can't get to absolute zero.

If you want another laugh, see if you can Google McGuire Electric Car. He has a motor which is 349% efficient - true! He measured it! With his Dick Smith DVM.

antiscab
Senior Member
Posts: 2139
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Changing an induction motor voltage

Post by antiscab » Fri, 05 Feb 2010, 12:10

free energy?

was that post meant for this thread?

i think you've lost me Nevilleh   *confused*

Matt
Matt
2008 Mazda 2 - EV Shop convert
2011 Blade Electron mk6
2007 vectrix - 117'000km
1993 Electrolux - needs batt and charger
1998 Prius - needs batt
1999 Prius - needs batt

Post Reply