Changing an induction motor voltage

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Stiive
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Changing an induction motor voltage

Post by Stiive »

cts_casemod wrote:
Johny wrote:
cts_casemod wrote:I need a 192Cell array and the BMS itself costs almost as much as the batteries themselves.
Have you looked into BMSs that handle 16 cells per board?


I have. The most simple ones are about 80$ each = 1300$ + Shipping + 20% VAT + Import taxes.

What I need is something "simple" with an output to an external contactor and without balancing, but I would like to have a reading of the individual cell voltages


If its something simple like that, your better off designing your own.
What exactly will the BMS be doing?
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Changing an induction motor voltage

Post by Johny »

What would be ideal for higher voltage pouch or Headway packs is a variation of Neville's BMS re-layed out for 16 cells per board.
If no shunting was really required then just leave the shunt resistors off the board.
viewtopic.php?title=low-cost-bms&t=2753
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Changing an induction motor voltage

Post by cts_casemod »

Johny wrote: What would be ideal for higher voltage pouch or Headway packs is a variation of Neville's BMS re-layed out for 16 cells per board.
If no shunting was really required then just leave the shunt resistors off the board.
viewtopic.php?title=low-cost-bms&t=2753


I have asked him how to get those boards, actually is the best solution I have seen.

He said on an older post that depending on the memory present on the master it could hold a couple hundred cells ok, maybe I could use the same master and conect my 4 packs (I may not have the same pack on the car all the time) which would be just great!

I was wondering, Will I be able to modify the VFD to work with only 320V? Just in case I had a problem with the packs and wanted to limp back home using the remaining good/charged ones.

Last edited by cts_casemod on Wed, 14 Nov 2012, 07:13, edited 1 time in total.
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Changing an induction motor voltage

Post by cts_casemod »

Stiive wrote:
cts_casemod wrote:
Johny wrote: Have you looked into BMSs that handle 16 cells per board?


I have. The most simple ones are about 80$ each = 1300$ + Shipping + 20% VAT + Import taxes.

What I need is something "simple" with an output to an external contactor and without balancing, but I would like to have a reading of the individual cell voltages


If its something simple like that, your better off designing your own.
What exactly will the BMS be doing?


I would like to have something like an analog multiplexer reading each cell using an optocoupler. The micro then would give me a reading that I could use to trigger the HVC and LVC and an alarm to indicate the battery was almost empty (Soc =<20%)

Using this method I could know if a cell was bad and where it was located on the pack.

Neville's BMS does all this with the option to disable the balancing which is very atractive.

My packs are removable (4x15Kg) so I will bring one home each time I use the car, so the Soc of the modules may not be the same.
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Changing an induction motor voltage

Post by ChrisRider »

I have a similar project coming up also, i wasnt sure if it was actually possible to physically change the induction motor voltage. Seems as though it may cost a bit in spare parts and materials, but i think it could be worth it as long as i dont break anything in the process, hehe
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Changing an induction motor voltage

Post by ale0502 »

Hello everyone, this is my first time I write in this forum.
First of all sorry for my English, I'm from Argentina.

I'm working on an electric conversion of a car from a three-phase induction motor and a bank of lead acid batteries. I'm developing the controller and all the staff.
I read the forum and understand some things and not others, plus the use of the language that makes I have to ask.

My motor is 4Kw , 2870rpm , 380V / 220V , 14.4A / 8.3A , 18 slots.
My battery bank is 120V, so I would like to modify my motor to have the best possible power with the voltage available.
What dou you recommend?

Because is a 2-pole, I can only lower the operating voltage to half, being of 380/2 = 190V, is that true??.

thank you very much in advance for sharing all this with the community
Last edited by ale0502 on Fri, 01 Apr 2016, 05:22, edited 1 time in total.
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Changing an induction motor voltage

Post by antiscab »

ale0502 wrote:
My motor is 4Kw , 2870rpm , 380V / 220V , 14.4A / 8.3A , 18 slots.
My battery bank is 120V, so I would like to modify my motor to have the best possible power with the voltage available.
What dou you recommend?

Because is a 2-pole, I can only lower the operating voltage to half, being of 380/2 = 190V, is that true??.


If you are very lucky, all 3 x 2 pole groups will be presently wired in series.
If that is the case, then you could rewire to parallel giving 190V star and 110V delta
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Changing an induction motor voltage

Post by coulomb »

antiscab wrote: If that is the case, then you could rewire to parallel giving 190V star and 110V delta

I'm quite rusty on this stuff, but I think with 120 VDC you will only get about 80 VAC (line to line). So that would only be 73% of full voltage for the motor. So you'll only get to about 72% of rated speed. You'll need a lot of current to get any power from this motor.

It will be a challenge.
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Changing an induction motor voltage

Post by Richo »

Mmm 2-pole isn't a great place to start.
The rewind would need to be ~50Vac to run on your 120V pack.
Peak ~5000RPM.
If your lucky you might get 20kW out of it.

Under 50kW the BLDC motors are probably a better option.

So the short answer is NO but the long answer is YES.
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Re: Changing an induction motor voltage

Post by ale0502 »

hello,

I know it's been a long time since this post.
But just now I have my motor with the coils reconnected and running.
It is a three-phase induction motor from:

2,2Kw/3CV
50Hz
4 poles
1430rpm
220V/380V

I already reconnected the 4 coils of each phase in parallel instead of in series and it works well. How do I know it works well? because I spin it with a controller in openloop mode and it works very smoothly in the whole speed range.
The problem starts when I want to make it run with the feedback control, where I need the motor parameters. In particular I find problems with the parameters of SLIP, is it possible that they have changed the minimum and maximum SLIP and therefore the straight V / Hz just by changing the connection of the coils? I guess not, because it is applying the same voltage as before to each coil and therefore the same current flows, but it does not work and I do not know what to try.

Thanks!
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Re: Changing an induction motor voltage

Post by weber »

I don't know about the slip, but the V/Hz should be 1/4 of what it was.
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Re: Changing an induction motor voltage

Post by francisco.shi »

The slip will be the same as before assuming you did not change the winding pattern only the turns.
When you enter the parameters you enter the scaled voltage and current.
Say you put 1/4 the number of turns. Then your current rating will be the times and your voltage rating will be 1/4.
Most inverters will just need this.
The only other problem you may have is that your inductance has been reduced by the square of the turns ratio. So say if you have 1/4 of the turns then the inductance will be 1/16 of before. What this means is that the ripple current at full voltage will be 16 times. This is probably not that much compared to the motor current. But effectively you have a motor with the times the power so you will need an inverter 4 times the size.
Say your motor was 415v and 10A and you put 1/4 of the turns so now your motor is 103.75v 40A. So now you need a 40A inverter. Your 10A inverter will not be able to drive it. At 103v your current ripple (that is the ripple produced by the switching frequency of the inverter) will only be 4 times but at 415 it will be 16 times.
If you are using a sensorless vector drive the inverter looks at the current and voltage being applied to the windings and using some fancy maths it can work out the position of the rotor's magnetic field. If your ripple has gone up then the inverter will have trouble getting a clean reading.
The slip value is used for the torque settings.
For an induction motor (very) roughly the torque is proportional to the slip. That means if you double the slip you will get double the torque. But there comes a point when it goes the other way. More slip = less torque. So the inverter has to know what that value is so the control loop does not go unstable. What that peak slip is will depend on the construction of the rotor.
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