Changing an induction motor voltage

AC, DC, amps, volts and kilowatt. It's all discussed in here
User avatar
weber
Site Admin
Posts: 2619
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Sat, 13 Jun 2009, 19:08

Hey, you had a coffee cup in the very first photo. You're just tormenting us with those chocky bikkies.

A 24 wire motor! 8 wires per phase! Man can you have some fun with that. As well as 1, 2 and 4 times overvoltage by series/parallel you can make 2, 4 and 8 poles just by which poles you reverse.

N N 8 pole (4 consequent poles)
N N

N S 4 pole
S N

N N 2 pole
S S

The 2 pole and 8 pole won't be very good of course. Can you devise some sort of brake and have the VFD tell you what it calculates the torque and efficiency to be, e.g. just before breakdown, in all these different configurations?
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sat, 13 Jun 2009, 19:30

Pole switching, yeh, I had thought about that. But then the mind wandered too much and I had a bikkie and got back to wiring. Image

The 8 pole is unlikely to work as there is no space between existing poles for a consequent pole to exist ?

The two pole should work but would probably prefer more of a square wave than sine wave drive ! And confuse the VFD control software ?

The plan is to couple this motor to another. Both on VFDs with data logging and see what numbers I can extract. The other lump would be a 2 pole 2.2kW motor.
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sat, 13 Jun 2009, 19:48

Just a research job for someone.... the varnish (goop as someone called it) on some motor windings. Is it dissolvable ? has it been baked ? can it be removed without damaging the enamel on the winding wire ?
This may be of interest on other motors. Image
iMiEV MY12     105,131km 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 » Sat, 13 Jun 2009, 19:51

acmotor wrote: Just a research job for someone.... the varnish (goop as someone called it) on some motor windings. Is it dissolvable ? has it been baked ? can it be removed without damaging the enamel on the winding wire ?
This may be of interest on other motors. Image


Not usually dissolvable, usually yes to the baking, and usually no to removing without damaging the enamel.

Motors being rewound are usually 'burnt out' in an oven with a controlled airflow, which pretty much gets rid (as smoke!) of everything except the iron, copper and fibreglass.

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sat, 13 Jun 2009, 19:58

Anyone else ???
TJ, that wasn't the answer I wanted !!! Image
I wanted you to say that it washes off with a bit of metho, or maybe coffee ? Image
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
weber
Site Admin
Posts: 2619
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Sat, 13 Jun 2009, 20:52

Yeah. I was just reading about the "burn out" thing yesterday. Apparently the hard part is making sure you don't burn out the varnish between core laminations, so they have to limit the max temperature.

I predict the 8-pole would work in the sense that the unloaded motor would turn at just under 750 rpm (at 50 Hz), but the torque would be practically non-existent. I believe there is one slot-spacing between the windings for a highly saturated consequent pole to exist in, but most of the flux will just go around the ends and be wasted.

The trouble with all this is that what works or fails with that baby 4-pole motor can't necessarily be aplied to the medium sized 4-poles we use in an EV. It's lap wound with all wound poles. They are most likely to be concentric wound with consequent poles.

But a 2 times rewire in addition to a delta config on a 415 V star motor would give an extremely useful 3.5 times overvoltage. That's still doable on a consequent pole job. Trouble is, they are usually 415 V delta. What's Red Suzi's motor? Concentric consequent and 415 V delta?
[Edit: Punctuation. And added "at 50 Hz"]
Last edited by weber on Sat, 13 Jun 2009, 12:54, edited 1 time in total.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sat, 13 Jun 2009, 21:01

TBA on Suzi's motor. It is 415V delta though.

2x voltage is better than 1.73x given that I can't get even get a 1.73x in Oz without re-wind.
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sun, 14 Jun 2009, 06:45

Progress has been made on the re-wire.

Image
To keep the wiring roughly in place I tied it with cotton string.

Image
The 24 flying leads from coils all labelled for future reference, although thanks to Mal it is quite easy to find out where they all go !

Image
There you go. That's tied up enough.

Image
Now megga test the insulation to frame and between coils. All >1000Mohm at 500VDC (would be nice to test at 1000V but my old megga....)

Image
All leads on terminals. Final insualtion test.

Image
Configured for 104V in Star (4 pole for now !)
All ready to spin !!!! Image






Wait for it !!!!   










6000RPM    



you little beauty !
        Darn font doesn't go any bigger !






Image
Proof of the pudding ! This little baby spins a treat.
6000 RPM at 200Hz (Danfoss in 0-1000Hz mode)
I told the VFD it was a 50Hz 4 pole 104V 1.5kW motor for starters. (remember it is 0.37kW nominally) I will review these settings once I get a feel for the motor.

Image
After a bit of playing around I let the little girl spin for 1 hour a 6000RPM and then measured the temperature. Ambient was 16.5°C.

Image
Bench of test gear for first testing runs. The laptop runs Danfoss MCT-10 software to configure drive and log run time data.
The Danfoss is an early model 5004 (2.2kW) It may be a bit short on output current (8.96A)
The blue Adam is an RS485 to USB convertor (later VFDs have USB + others comms built in)

Image
So far this is the loading system.
The 'fan belt' got smoked so I will have to set up another emotor as the load.

I took some run time data and I will post it when I have run it through excel..... and set up some proper dyno system.

The sounds this motor makes are pure 'electric' !! Image
Ho Hum, this is probably where Solectria were 15 years ago Image

edit: schpelung
Last edited by acmotor on Sat, 13 Jun 2009, 22:26, edited 1 time in total.
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sun, 14 Jun 2009, 08:15

Just a quick look at some data before I go to sleep....

Image

This is short loads applied with the 'fan belt' before it got smoked.
The power went over 2kW at 6000RPM with little change in motor voltage so the VFD wasn't having to try hard to hold speed. (still short of the breakdown torque) Motor current around 4.5A

Torque at each revs (much the same) was all I could apply by hand so = more kW as the revs go up.

Now for a proper test rig !!
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
weber
Site Admin
Posts: 2619
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Sun, 14 Jun 2009, 17:33

Woohoo! This is great stuff. I can hardly wait for the next installment.

I'm keen to know both breakdown torque and the continuous torque at which it runs at say 50°C after an hour, at 200 Hz.

But I guess you'd then have to wire it back to its original settings to do the same at 50 Hz for comparison. But easy to do, because you were smart and brought all 24 wires out.

Thanks so much for this.

By the way, coulomb and I have done the repeat 3C TS discharge with max cooling with your BMS board in place. Sorry we haven't plotted and posted it yet, but Coulomb has not been well. Probably flu contracted from a permanently excited squirrel cage. Image
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sun, 14 Jun 2009, 19:11

Just give him some OINKment ! Sorry, swine of an idea. Image

Nominal torque at 50Hz 104V now should be same as 50Hz 415V was originally unless elvis is alive, but I will confirm.
The VFD increase of v/f under load may make the max torque interesting though.

The low temp rise was a bit surprising ~10°C at 6000RPM, but then the little fan is competing with takeoff at the local airport (and consuming power).

Now we just need to machine some PMs into the rotor like prius does....
Image
iMiEV MY12     105,131km in pure Electric and loving it !

a4x4kiwi
Senior Member
Posts: 772
Joined: Thu, 03 Jan 2008, 19:04
Real Name: Malcolm Faed
Location: Australia
Contact:

Changing an induction motor voltage

Post by a4x4kiwi » Sun, 14 Jun 2009, 21:30

Great work Tuarn!

Regarding your settings, understanding they are to be refined.

I would have thought that setting the VFD to 104v might have limited the maximum voltage to the motor, apparently not.

As the motor is not loaded, it probably doesn't matter much.

I wonder if setting it 200Hz, 415v and 1.5kw would have the same effect?

Mal.
Last edited by a4x4kiwi on Sun, 14 Jun 2009, 11:32, edited 1 time in total.
Silicon is just sand with attitude.

Blog: http://malfunction.faed.name

a4x4kiwi
Senior Member
Posts: 772
Joined: Thu, 03 Jan 2008, 19:04
Real Name: Malcolm Faed
Location: Australia
Contact:

Changing an induction motor voltage

Post by a4x4kiwi » Sun, 14 Jun 2009, 22:01

Using Torque = (9550xPower)/RPM

The original rated torque was 2.4Nm. (.375kW and 1500RPM)

Based on the graph and the ability of Tuarn to hold the belt (and the VFD torque boost)...

@1500RPM T=4.5Nm
@3000RPM T=3.0Nm
@4000RPM T=2.8Nm
@6000RPM T=3.3Nm

Nice.
Silicon is just sand with attitude.

Blog: http://malfunction.faed.name

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Sun, 14 Jun 2009, 23:22

Mal, what I am telling the VFD is basically the v/f ratio (AFAIK) by setting 104V 50Hz. So 415V 200Hz would be exactly the same ? i.e. 2V/Hz

The VFD just supplies v/f up 'till it runs out of Volts or is current limited by VFD Imax or settings.

If load dependent v/f is enabled then VFD will increase v/f by as much as it can until it reaches the torque limit setting in setup.
Note, there is little option for VFD to increase v/f once you reach 415VAC (or DC bus voltage / 1.414) so boost is limited at full speed to emotor nominal Tmax. Probably correct since too much extra voltage at this stage will enter magnetic saturation.

The guessed resistance and reactance by VFD prior to AMA may be wildly though depending on the start numbers ? Haven't given this much thought.

This VFD (8.96A) may run out of current since the emotor may pull 12A at Tmax. Next option would be to connect to the bigger girl 5042.

Do you agree with any / all ? Image
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
woody
Senior Member
Posts: 1714
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

Changing an induction motor voltage

Post by woody » Mon, 15 Jun 2009, 02:49

acmotor wrote: Do you agree with any / all ? Image
Loving it all.

Current usage is only linear to approx 70% of Tmax. It's about 4x current for a Tmax of 3.

So maybe 15 amps?

I'd also like to see how much torque boost mr Danfoss gives, and how much you can get by changing V/F and how much extra efficiency you can get by lowering it a bit...

Cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Mon, 15 Jun 2009, 03:37

Ahhh, well the idea of a VFD is that it generally looks after the boost and cutback of v/f to achieve performance and economy. The VVC+ space vector control... all that.
If you set the 'nameplate spec' voltage higher the motor runs more current than required at low load. If you set it lower but increase the load compensation it seems to run much the same if load dependent v/f is enabled although it is more prone to lose the motor if torque increases rapidly.

But with a hacked motor ? In fact when I told Dan it was still a 0.37kW motor it still ran the same (having set current and torque limits to drive max). There's more smarts inside there ! Image
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
Bluefang
Groupie
Posts: 90
Joined: Wed, 13 May 2009, 22:37
Real Name: Derek Hohmann
Location: Gold Coast, Queensland

Changing an induction motor voltage

Post by Bluefang » Mon, 15 Jun 2009, 04:50

Wow, this is really great information. Image
Now for a question, you took a .37kw industrial motor and multiplied its power by 4 to get a 1.5KW emotor. I assume this would work with larger motors? Atm there are 2 motors at my work that are not used at all and have been collecting dust for a number of years i would assume but the amount of dust over them. They are roughly 45-50kg motor only and 3phase power.

Their specs are
V                   Hz       R/min       KW       A
254-277 o     60       3425        7.4      21.6
440-480 y     60       3425        7.4      21.6
254-277 o     60       1650        5.5      17.3
440-480 y     60       1650        5.5      10

So looking at that the max is 7.4....would that mean they are capable of 30KW?
Last edited by Bluefang on Sun, 14 Jun 2009, 18:51, edited 1 time in total.

User avatar
weber
Site Admin
Posts: 2619
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Mon, 15 Jun 2009, 05:55

I think you've hit the jackpot there Bluefang. Are those two identical motors, where each one has all four of those spec lines. If so, it's a 2 speed motor and should provide lots of options without even having to open it up. It can apparently be wired for 2-pole (7.4 kW) or 4-pole (5.5 kW). And the fact that it has a 265ac V 60 Hz (220 Vac 50 Hz) delta configuration is great.

How many terminals are inside the terminal box? What is the height of the shaft center above the plane of the feet, in millimetres?

BTW, I think you'll find the second current is 12.5 A, not 21.6 A.

They would almost certainly be capable of 30 kW for a few minutes.

Induction motor ratings are continuous ratings. They can typically do 3 times that for short bursts by allowing them to draw more current. Do they have a Tmax/Tn figure or a make and model number?

While a 4 times overvolted/oversped motor may have nearly 4 times the peak power, I do not believe it will have 4 times the continuous power but only about 2.6 times. Approximately the frequency ratio raised to the the power 0.7. 4^0.7 = 2.6. Although that does assume the same cooling, by a separate fan, not one on the motor shaft.

I think acmotor's 4 times overvolted 0.37 kW motor will only be capable of about 1 kW continuous because of the increased iron losses at 200 Hz.

Your motors probably can't be rewired for 4 times overvoltage in the same way as acmotor's toy one can. But they can probably do 2 times by wiring the poles in parallel, and another 1.4 times by feeding 380 Vac to them in delta. Provided they can survive mechanically, running at around 5000 rpm. You may need to get them balanced to do that. At that speed you'd probably get about 11 kW continuous and maybe 45 kW peak.

If you used in 2-pole delta and only overvolted it by 1.4 times with the 380 V into the 265 V delta. I'm guessing you'd get about 9 kW continuous but only about 30 kW peak. Really not sure about any of these figures. They could be out by +-50%.

What city are you in?
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

vince
Groupie
Posts: 173
Joined: Sat, 31 May 2008, 14:26
Real Name: vince massa
Location: On.Canada

Changing an induction motor voltage

Post by vince » Mon, 15 Jun 2009, 06:06

Along with Bluefang's question-what would the efficiency comparables be utilizing said motors in their present states as to their modified states?
Can somebody at some point put in simpler language a summary of all the above?It is dazzling what your saying but i havent as yet figured out where your going with it but it sounds like some sort of breakthrough i would like to know about!

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

Changing an induction motor voltage

Post by acmotor » Mon, 15 Jun 2009, 06:50

Bluefang, you could argue to the guys at work that those '60Hz' motors are only worth a carton since we have 50Hz in Oz and you best move them so they don't get used locally. Image

Looks like they would be worth having.

Hmm, I could use one on the front axle and one on the rear !   Image
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
woody
Senior Member
Posts: 1714
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

Changing an induction motor voltage

Post by woody » Mon, 15 Jun 2009, 14:12

Vince, acmotor is elegantly reconfiguring the 4 windings per pole to run in parallel to allow 4 times current at 1/4 voltage at the same speed / power / frequency, but also 4 times current at original voltage for 4 times power / speed / frequency. This is something which could already be acheived with a rewind, acmotor is just bypassing almost of the rewind labour / expense.

Bluefang - the 5.5 will already do about 25kW peak with a 400V VFD connected to the delta terminals.. If it's possible to do a similar thing as acmotor's done you'll get near 100 with a big enough VFD at 10,000 rpm! I'd keep it under 6000 rpm unless you have a concrete - reinforced engine bay though.

Cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
coulomb
Site Admin
Posts: 3761
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by coulomb » Mon, 15 Jun 2009, 14:42

One of the neat things about rewiring or rewinding is that we believe that the continuous power of the motor goes up as well. Unfortunately, not by the same factor as the voltage, so 4x rewiring won't quadruple the continuous power. The iron losses go up with the higher frequency; the copper losses are about the same as each wire sees about the same current as before. So you might get 2.5x the continuous power rating for the same motor.

For lower performance conversions (like my White Suzi), continuous power is relatively more important than for high performance conversions (like our MX-5). So to choose the right motor for a Barina-class vehicle, you can probably choose the new continuous power to enable your cruising speed, e.g. 100 kph continuously, or maybe you'd be happy with less.

More info in this in the big AC motors, Multipoles and Torque thread about here.

But it does smack of "getting something for nothing", so that's one of the reasons that we are very much looking forward to some more actual results.

Edit: it's 2.5x from Weber's graph
Last edited by coulomb on Mon, 15 Jun 2009, 04:43, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

a4x4kiwi
Senior Member
Posts: 772
Joined: Thu, 03 Jan 2008, 19:04
Real Name: Malcolm Faed
Location: Australia
Contact:

Changing an induction motor voltage

Post by a4x4kiwi » Mon, 15 Jun 2009, 15:50

To follow on from Coulomb, the motor is going to run hotter due to the increased power, so you will need to cool the motor more effectivly.

Active cooling will be essential for this kind of upgrade.

My 15kw got rather toasty after a hill climb, and the electric fan solved that problem.

Silicon is just sand with attitude.

Blog: http://malfunction.faed.name

User avatar
weber
Site Admin
Posts: 2619
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Changing an induction motor voltage

Post by weber » Mon, 15 Jun 2009, 17:09

vince wrote: Along with Bluefang's question-what would the efficiency comparables be utilizing said motors in their present states as to their modified states?
I expect the efficiency at rated torque to actually increase slightly. That is, the losses will be a smaller fraction of the input power. But the absolute losses (the energy that goes into heating the motor) will increase. I think that for a 4 times overvoltage/overfrequency the losses will be about 2.5 times greater at rated torque.
Can somebody at some point put in simpler language a summary of all the above?It is dazzling what your saying but i havent as yet figured out where your going with it but it sounds like some sort of breakthrough i would like to know about!

As others have said, the idea of getting a motor rewound to make it give full flux and hence full torque up to a higher speed (and hence more power) is well known. What will be new here will be the eventual demonstration that you can achieve a similar effect (albeit limited to specific ratios) by the cheaper method of opening the motor up and finding the right place to cut and join some wires in order to wire things in parallel that were previously in series.

I say "eventual", because the motor hasn't yet been run with a consistent or measurable mechanical load on it, to get some real figures for peak and continuous power. But give the man time ...

We certainly aren't getting any energy for nothing. If you make a 7.5 kW motor into a 30 kW motor by rewiring and overspeeding it, you then have to have a VF drive and batteries that can supply energy at the rate of 30 kW plus losses.

We seem to be getting a smaller lighter motor for nothing, but we aren't really doing that either. What we're doing is taking advantage of the fact that industrial induction motors are very conservatively rated. They are rated at what they can do for 40,000 hours (about 4.5 years!) without stopping. In our EVs we only need them to perform for about an hour at a time, and only to work really hard in bursts lasting a few seconds.

When we rewind or rewire and overspeed a motor like this we are increasing the volt per turn and volt-per-second per turn stresses on the windings, which may eventually cause failure due to insulation breakdown, and we are increasing the centrifugal stresses on the rotor which may eventually cause fatigue failure of the aluminium end-rings.

But we can get away with it because we are only subjecting it to these stresses for at most a few minutes in every day. So we are trading operating life (but not calendar life) for power in a way that makes a lot of sense for an EV application.

One trick used in high speed induction motors is to put steel retaining rings around the aluminium end-rings on the rotor. That sounds like something that could be added to an existing industrial motor by an EVer with a suitable lathe. But not sure if it's worth the trouble.

We are also stressing the bearings more. More precise rotor dynamic-balancing (and balancing of any coupling or hub or flywheel) is required to minimise this.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
Bluefang
Groupie
Posts: 90
Joined: Wed, 13 May 2009, 22:37
Real Name: Derek Hohmann
Location: Gold Coast, Queensland

Changing an induction motor voltage

Post by Bluefang » Mon, 15 Jun 2009, 17:39

I dont have many measurements atm but here are some photos, total motor length including pulleys is 550mm, width/height is 250mm and the motor casing seems to be about ~300mm. Ruler length is 600mm

ImageImageImageImageImage
Last edited by Bluefang on Mon, 15 Jun 2009, 07:41, edited 1 time in total.

Post Reply