ABB motor and VFD selection

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e-ghia
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ABB motor and VFD selection

Post by e-ghia » Wed, 03 Jun 2009, 22:45

Let me first say that I’ve read the epic thread, AC motors, multipoles, torque, and the expertise of the users of this forum is phenomenal. That’s not to say that I understood it all, but I’ll be reading it again soon. I’m new to the forum and part of a group of four students that is converting a VW Karmann Ghia, and we have decided to go industrial AC but are struggling with the motor/VFD selection. Clearly, many of you are experts here, and I’m hoping that you can point us in the right direction.

Here are the goals and constraints:
105+ kmh and 65+ km range (yes, lofty I know)
SLA Batteries due to cost (considering the Greensavers used by Mal)
Drag area (CdA) = 0.65 m^2; Crr = .010 (determined by roll-down test)
Original Curb Weight = 840 kg
Keeping the clutch, gearbox, and original transmission (but we could be persuaded otherwise)

Here’s the catch. Due to a relationship that we have with a vendor, we can get a very good deal on the motor and VFD, but they must come from ABB. http://www.abb.com/ It has been suggested to me by an ABB rep that we use the ACS800-U1 VFD, but there seem to be several models of these.

Most of all, we have little idea how to size and select the motor appropriate for our application.

I notice some of you have experience or knowledge with ABB products, so please offer your advice and input. I should also mention that we are not subject to MEPS limitations as we are in the US, so that might offer some more options. I can provide more information about the donor chassis/setup, and any suggestions or tips are greatly appreciated.

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Post by Johny » Wed, 03 Jun 2009, 23:11

What - no takers on someone ASKING for us to gasbag.

I'll start.
I'll assume you really are going to keep the gearbox and clutch (until someone convinces you otherwise).
7.5kW to 11kW, 2 pole motor in the smallest frame size you can get it. Metric frame size would be 132. I think that translates to a 210 in the US. Ensure it's an aluminium frame motor - lighter.

If you want to keep the DC Bus (battery voltage) as low as possible, get a 220V, 3 phase motor that way a DC Bus of about 320 VDC should run it OK. Going for higher voltage (such as we are forced to do by availability of VFDs) limits battery choices a bit.

With a DC Bus of 320 VDC you can use a 220V VFD.
Size the VFD at least 3 times the motor power rating.
I.e. If using a 7.5kW motor, get a 22kW VFD. Make sure the VFD will give you 150% of its rating for 60 seconds as well. 7.5kW motor would use say an ACS800-U1-0030-2. You may get away with the next size down as it is the smaller enclosure size.

That allows for using the peak motor torque almost continuously without the VFD cutting back the power when it gets hot.

I didn't quite understand the CD of the car - was that 0.65?

I think your target speed and range are good ball park but range not at top speed - probably 65km at 60-70km/hr.

There - kicked off. Start shootin' guys. Image

Edit: Corrected suggested ABB VFD.
Last edited by Johny on Wed, 03 Jun 2009, 13:59, edited 1 time in total.

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Post by woody » Wed, 03 Jun 2009, 23:28

Hi & Welcome!

which uni are you at?

You'll need two sets of motor + VFD. One spare which I will look after for you.

Greensavers will be about 350kg / AU$3000.
Your budget may be able to stretch to 10Ah Lithiums (e.g. EVPST) for about AU$7000, but only 100kg. You may save a lot of that $4,000 in structural work to make a tiny dak-dak carry 350kg.

CdA is not drag area, but rather Coefficient of drag (Cd) times the frontal area (A). Looks like you have the A, but not the CD.

Keeping the gearbox makes sense since it includes the diff.

Therefore a 2 pole motor is probably a good bet, the one Weber and Coulomb ordered is a 131008-HSE is wound 400V/240V which means you can spin it to 5000 at full torque.

Motor needs an encoder which ABB can provide.

A controller to take full advantage of this would be about 75kW nominal, 415V AC.

Controller needs:
torque control
encoder input
DC bus power option
dynamic brake

From memory the ACS800 does all that, one of right size should weigh about 50kg.

cheers,
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Post by woody » Wed, 03 Jun 2009, 23:43

Johny wrote:7.5kW to 11kW
Johnny's right, it will still "work" with a tiny motor, but it's best to start by asking big (the 131-008HSE is 22kW , 2 pole and there's a quote on this forum for about $2600.)

The VFD you'll need will be at least 4 times the nominal rating of the motor.

e.g. 11kW motor -> 45kW VFD will give you about 60kW on the road.

22kW motor -> 90kW VFD will give you about 120kW on the road.

According to this guy: the Cd is 0.4, the frontal area is 26 square feet (2.15m^2). Ignore the performance + motor specs on that one, it's had a few mods since it left the factory (0-60mph < 5 secs).

cheers,
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Post by Johny » Wed, 03 Jun 2009, 23:59

Yes woody is right. My conservative figure are for a "daily driver". Not too zippy but able to keep up with traffic.

I also made an error in that I did not check the VFD voltage rating for the one I suggested. The correct 220 V VFD (assuming 320 VDC would be ACS800-U1-0030-2.

You may have trouble with lead-acid (or lead other) with a 22kW motor.

Check battery pack current ratings for the same time that your VFD and motor can sustain high power. Best if all 3 can do it.

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Post by woody » Thu, 04 Jun 2009, 00:03

Oh, and I missed that you were US-based (thanks for translating to metric for us :-), you'll need 50 Greensavers to get a chance of 65km range, i.e. 600V DC into a 415V AC VFD.
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Post by juk » Thu, 04 Jun 2009, 01:14

On a side note, the 11kV 1.3MW (not a typo) VFD at work broke yesterday. It's been two days with all the gurus looking at it and we're still down. It broke without warning, suspected thunderstorm activity though. And yeah, it's an ABB. It's also almost 1 of a kind.

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Post by coulomb » Thu, 04 Jun 2009, 06:48

woody wrote: Therefore a 2 pole motor is probably a good bet, the one Weber and Coulomb ordered is a 131008-HSE is wound 400V/240V which means you can spin it to 5000 at full torque.

Motor needs an encoder which ABB can provide.

A controller to take full advantage of this would be about 75kW nominal, 415V AC.

I think that might be over the top for a tiny car, and may well tear the gearbox to shreds, and overtax the lead acid batteries.

I'd suggest 11 kW, or 7.5 kW if you can find one wound for a low voltage, or rewire for a low voltage. I plan to rewire my 415 V motor for 1/3 voltage, or 138 V. That way the motor becomes about a 17 kW continuous motor at around 4500 RPM (oops, different with nominally 60 Hz motors; around 5400 RPM. You may need to get it balanced for higher RPM.) You'll get about three times that peak, or about 50 kW, which should be plenty for a small car.

Look at some of the options you can get with ABB motors; M comes to mind. It may be low enough voltage "out of the box" to get away with a 7.5 kW nominal. Note that if you overvoltage significantly (2x or more), you will want a 4-pole motor, not a 2-pole. Don't look at 6-pole and above.

Note that the 22 kW motor that we ordered is a super special model that crams the most power you can get into a 132 (metric) frame (or so we've heard). It also takes 5 weeks to make and 9 weeks to ship (to Australia; to the US should be a fair bit quicker).
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ABB motor and VFD selection

Post by e-ghia » Tue, 16 Jun 2009, 21:26

Whew, that was a loooooooong week without the forum.

Thanks for sharing your expertise guys. As most of my EV research has gone for the past year, the answers I seek only make me ask more questions. First, I'll answer some of yours.
Johny wrote: I didn't quite understand the CD of the car - was that 0.65?
No, it's actually closer to 0.32-0.33. I'll explain...
woody wrote: CdA is not drag area, but rather Coefficient of drag (Cd) times the frontal area (A). Looks like you have the A, but not the CD.
Yes, CdA is the product of the Coefficient of drag and frontal area. Let me explain.
woody wrote: According to this guy: the Cd is 0.4, the frontal area is 26 square feet (2.15m^2)
Yes, but that's the problem. It's difficult to measure the frontal area with great accuracy. I've measured the car and 26 sqft is way off. Having said that, theoretically both the Coefficient of drag and frontal area are constant, and it's easier to solve for the product which is sometimes called the drag area.

The frontal area is closer to 21-22 sqft, but I can't be sure. However after analyzing the data from roll-down testing, I can say that the CdA is just under 7 sqft or about 0.65 m^2. Based on this and a Crr of about 0.010 (also calculated from roll-down testing), I made a power model. This is similar to some of the fantastic spreadsheets that some of you have, and I’d really appreciate your input. Please forgive the units at the bottom in mph, but assume 65 mph = 105 km/hr.

Image


The model shows that to maintain a speed of 105 km/hr requires about 13.4 kW. Assuming (on the safe side) a mechanical efficiency of 0.90 and electrical efficiency of 0.80, we would need around 18.6 kW to maintain 105 km/hr.

Based on this, I'm looking at the ABB 131-317 and 131-007 which are rated at 18.5 kW continuous. Am I on the right track? Some suggestions have been an 11 kW motor, so is 18.5 overkill? Also, the prevailing sentiment in several threads is that the VFD should be 3-4x the nominal motor rating. Could someone explain why that is? My assumption is that the larger VFD will not be current-limited in providing more torque past the nominal RPMs. Again, am I on the right track?

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Post by Richo » Tue, 16 Jun 2009, 21:39

It would be 18.5kW at 400V at 50Hz
An 11kW at 400V at 50Hz could be rewound for say 220V (Common rewind)
This means 400/220*11kW = 20kW approx continuous.
BUT an AC induction motor has a peak torque multiplier of 2-4 depending on model.
Typically Tmax~3 x Tnom So the 11kW now rewound for 20kW would peak at 20x3=60kW

But to achieve the peak 60kW you need an inverter to supply 60kW.
So the inverter would have to be 60kW or bigger to supply the peak.

The motor I have for my BMW is 18.5kW@400V rewound for 220V
But running off 400V it is now 400/220*18.5=33kW
And peak is around 3.5 x 33kW = 115kW

How big the motor is depends on how fast you want to get to 65mph.
A bigger motor will get you to top speed quicker.
A small motor will be cheaper to buy.
So the short answer is NO but the long answer is YES.
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Post by coulomb » Tue, 16 Jun 2009, 21:55

Based on this, I'm looking at the ABB 131-317 and 131-007 which are rated at 18.5 kW continuous. Am I on the right track?
Close. But a few flaws.
First, Motors, and even controllers, are rated im terms of mechanical output (for an "average" motor in the case of controllers). So no need for the additional efficiency factors.
Next, the nominal power of a motor is based on its built-in fan. For EV use, we'd normally discard that fan, because it's not enough cooling at low revs, and too much load at high revs. So we use computer or automotive "thermatic" fans instead. So now the nominal output power of the motor is a bit rubbery.
But thirdly, around here, we like to rewind or rewire our motors for lower voltage. This increases the peak power available, but also increases the continuous power.

Let's say you picked an 11 kW nomonal motor, and for arguments sake let's say it will take 12 kW nominal with really good external cooling. Usually, these would be 415V motors, but we might be able to rejig the connections in the terminal box from star to delta, or snip some wires inside as acmotor and I are attempting, or get the motor rewound for 240V delta, or simply order one with the "S" option (meaning ~400V star, hence around 230V delta). So now, the 415 V 50 Hz motor has become a 240 V motor, a difference of 1.7 or so. With our industrial controllers and enough battery voltage, we can still apply 415V to the motor. We know it can take the voltage, because it could have had 415V applied in star mode. Or even 720 V. Increasing the voltage and speed of the motor with a constant torque load does not increase the current. It does however increase the iron losses, and minor losses due to bearing friction and windage. Taking all that into account, we can increase the voltage and speed by 1.7, keeping the torque constant, and end up with a motor that is 1.7 times as powerful. Say 20 kW in this case. It probably won't be able to maintain 20 kW continuously, but only because of the iron (etc) losses, not copper losses. So we look up Weber's graph, and come up with (say) 1.5 as the increase in the continuous power of the revoltaged motor. So this nominal 11 kW motor with our external fans and rejigging is now an 18 kW continuous motor, more than you need. It will take 18 kW all day long, and even will take 110% of that for an hour.

So now you can see that perhaps a 7.5 kW motor might do you. That's a good thing, because 7.5 kW motors are usually 132 frame, and plenty heavy (~55 kg aluminium, 75 kg cast iron like mine). An 18.5 kW nominal motor will be at least a 160 frame, and would weigh well over 100 kg. Driven properly, it will rip the teeth off your gearbox.

Controllers have continuous and peak ratings too. Sometimes, their power is given as two figures, like our 75/90 kW. The 75 means it will take 75 kW (mechanical) all day, and 50% more for short peaks. The 90 says it will take 90 kW all day, with 10% more for longer periods. EV usage is very peaky, so we go with the 75 kW number, allowing us to push out more than 100 kW for brief burts.

So at minimum you want a controller whose low power figure is around the 15 kW area, as long as about 150% of that (22.5 kW) is enough for your acceleration and hill climbing. Remember that an induction motor, in addition to all the overdriving we have been talking about, also has breakdown torque, which it can dish out for brief bursts. This is typically about 3 times the nominal power, so to get the most out of our 11 kW nominal motor we would need about a 20.5 * 3 ~= 60kW, so about a 40kW (low power number) controller. You have to decide if you want to pay the extra money for the more ICE-like performance that this will allow you, or some figure in between the bare minimum of 15 kW and the ideal size of 40 kW.

Edit: screwed up the controller numbers
Last edited by coulomb on Tue, 16 Jun 2009, 11:59, edited 1 time in total.
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Post by coulomb » Tue, 16 Jun 2009, 22:03

Richo wrote:How big the motor is [needs to be] depends on how fast you want to get to 65mph.
A bigger motor will get you to top speed quicker.
A small motor will be cheaper to buy.

A really small motor won't even give you the maximum speed you want, and will be very slow getting to that maximum speed.

So as Rico points out, you need to consider not only the maximum top speed (which also will require the right gears and/or diff and/or number of poles etc), but also acceleration and hill climbing performance. Also straight out driveway climbing torque if you don't keep the gearbox.
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Post by e-ghia » Wed, 17 Jun 2009, 14:27

I hate to be a pest, but let me see if I’m closer now.

ABB has a 15 kW in a 132 frame: model # 131 316. If I order this as “HSE” (as did weber and coulomb) where the S denotes the 240 delta or 400 star, then the nominal power is 15*400/230 = 26kW continuous and about 78 kW peak.

I would then choose a VFD that is rated at 400V and near the 75 kW range. The VFD sends 400V to the 230V delta resulting in the higher than nominally stated power, but I’ll need external cooling.

Am I right so far?

To supply the motor with 400V, I believe I need to supply the VFD with 400*1.73 = 692V. I was originally planning 50 Greensavers (or another small UPS battery perhaps) which would give me 600V. I think this means that the motor will see 600/1.73 = 347V. Is that to say that the 15 kW nominal motor gives 15*347/230 = 22.6kW? Or would the VFD not want to operate at less than 380V?
coulomb wrote: An 18.5 kW nominal motor will be at least a 160 frame, and would weigh well over 100 kg. Driven properly, it will rip the teeth off your gearbox.
Will the 15 kW motor still rip apart my gearbox? Would the 11 kW motor really give satisfactory performance?
One more question: If an 11 kW motor can be “overvoltaged” to 18 kW, is there any advantage to just using an 18.5 kW motor at 400V?

Thanks again for all the free advice and sharing your words of wisdom.

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Post by woody » Wed, 17 Jun 2009, 15:57

You have it right up to where you ask if you have it right.
You're not a bother, you're feeding our addiction.
Bonus is that 400v ac is sqrt(2) x 400 = 587 volts peak to peak so 50 greensavers is tops.
Torque will break your gearbox, not power - check with VW nerds how much torque a standard gearbox can take, and add some since you won't be revving it to 6000 and dropping the clutch.
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Post by Johny » Wed, 17 Jun 2009, 15:58

Hi e-ghia.
Last bit first. Battery voltage only needs to be 1.414 times your planned AC voltage. So for 415 Phase to Phase you need 586 VDC of batteries. 600 VDC is a good round number to use.

Your 15kW over voltaged motor still has the same torque so rewinding or ordering a lower voltage and driving it "harder" actually results in more power just because you start loosing torque due to lack of voltage
at a higher RPM. Since it has the same torque, the gearbox should last the same as a "standard" 15 kW.

For instance a 15 kW 4 pole motor develops 98 NM of torque (rated, not peak) at 1470 RPM

Since Power(kW) = (Torque(NM)/9550)*RPM
(98/9550) * 1470 => 15.084 kW

But ACIM torque drops off when we can not maintain the volts per hertz beyond what our batteries can supply. With a lower voltage wound motor, you tell the VFD it's a higher frequency motor so that you get full torque at say 3000 RPM
(98/9550) * 3000 => 30.78 kW

Same torque - more powerful motor.

Edit: Fixed some numbers.
Last edited by Johny on Wed, 17 Jun 2009, 06:01, edited 1 time in total.

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Post by Bluefang » Wed, 17 Jun 2009, 16:55

Wow, half this is flying over my head but with changing the motor from 15kw to 30kw isnt this going to double the current needed causing the motor to get alot hotter? I know you guys talked about extra cooling, but that sounds like alot of extra heat too.

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Post by coulomb » Wed, 17 Jun 2009, 17:32

Bluefang wrote: with changing the motor from 15kw to 30kw isnt this going to double the current needed causing the motor to get alot hotter?

No, you double the voltage, same current, hence double the power. Assuming the same torque load, and doubling the speed. Current is close to proportional to the torque. So the copper losses (I^2R) are about the same.

It will dissipate some more heat, though, due to increased iron, friction, and windage losses. Basically, everything is happening twice as fast, so the hysteresis loss happens twice as fast, eddy currents are worse, bearings dissipate twice as much heat, and there is (at least) twice as much loss churning up the air. Some of these go up with the fourth power of speed. Weber has calculated them in another thread, and come up with a graph of how much continuous power will increase for a given overvoltage ratio, assuming you can't dissipate any more heat than would be produced at nominal conditions.
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Post by weber » Wed, 17 Jun 2009, 18:04

Bluefang wrote: with changing the motor from 15kw to 30kw isnt this going to double the current needed causing the motor to get alot hotter?
Yes you're doubling the current, but this doesn't produce any more heat. Why? Because when it was rewound for half the voltage it was given half as many turns of wire, but using wire with double the cross-sectional area. Or, if the revoltaging (revolting???) was done by talking windings that used to be in series and wiring them in parallel, you get the same result. The amps per square millimetre of wire cross-section are exactly the same, so no more heat from that source.

However the motor does get a little hotter, but not because of the doubled current, but because of the doubled frequency. My rough rule of thumb, (based purely on theory I've read, and yet to be confirmed by any kind of reality) is that the continuous power rating (which is all about heat dissipation) should go up as approximately the 0.7 power of the rewind ratio. So a 2 times rewind should give about 2^0.7 ~= 1.6 times the continuous power. But the peak power should go up by the full amount. You need to know the Tmax/Tn figure for the motor to calculate peak power (typically 2 to 4).

Ah Woody, you are so right (feeding the addiction). So I'm going off to do some real work now. Well soon ... Really ... I can give up any time I want.
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Post by coulomb » Wed, 17 Jun 2009, 18:12

Sigh. While Weber and I seem to be saying the opposite (no current doubling, yes current doubles) it's really the same thing, it just depends on where you compare to.

I guess the obvious reference is nominal voltage and current; compared to those, yes the voltage stays the same and the current doubles. But once you rewire for half voltage, the voltage is halved and the current is doubled, for the same power. Relative to that point, voltage doubles and the current stays the same.

As Weber points out, the important point is that the amps per square millimetre are the same, so no extra copper loss from that source.
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Post by Mesuge » Thu, 18 Jun 2009, 06:54

Hi e-Ghia> Good approach, that's an idea to consider: ABB motor + VFD combo => demand discount!
Obviously the pricing for this brand is on the expensive side. Here is
some "fly by night" pricelist not sure whether this is the factory one,
which is usually shaved a bit off at the dealers..

http://www.joliettech.com/abb_acs-800_a ... atings.htm

ABB VFD: high efficiency, brake chopper inside, good connectivity
options, form factor/size on par with other big brands, and probably
good support from the manuf.

--

Image
linky about new ABB Wisconsin assembly line, frame sizes for vfds..
btw. at Danfoss this is done completely by robots..

"Ready For Production! -- Assembler James Davis puts the finishing
touches on a new R5 frame size unit from the new ABB ACS 800 DriveIT
Low Voltage family. "

-> from the depths of the internets, what is interesting is the frame
size in comparison to human figure. The largest one from R5 cat.
available, according to table is ACS800-U1-0070-5 (55kW - 10sec) peak
drive..
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Post by e-ghia » Fri, 28 Aug 2009, 15:28

I have received my VFD from ABB: the ACS800-U1 70-5. It's rated at 55kW and 96A (138A max).

But I still have no motor...

The folks at ABB were rather convinced that an ACIM was not the best choice for me, and suggested that I check out their HDP servomotors.

Does anyone have any knowledge or experience with these? We've been considering using the CM1.7.

We are also looking at servomotors from SEW Eurodrive. This company is rather "student friendly," and we are considering their CFM112L servomotor. Any thoughts or experience on this from all the AC gurus is greatly appreciated.


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woody
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ABB motor and VFD selection

Post by woody » Fri, 28 Aug 2009, 16:06

Looks good, 100Kw max in 91kg. Need to run some numbers for you...
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Richo
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ABB motor and VFD selection

Post by Richo » Fri, 28 Aug 2009, 21:03

91kg is a CM1.
For S1 duty the most nominal power is 21kW.
The Tm/Tn=3.2 so this is 67.2kW peak for 91kg.
Eqv motor is an 11kW 4-pole 50Hz 400V motor.

In comparison I would use the CM4.3.
This can produce 107.1kW peak.
It weighs 151kg which is 41kg more than my current motor.
For the same power.
The only advantage here is the small diameter of 250mm (eqv 125 frame).

You are also paying for the built in encoder which I'm sure isn't cheap.
So the short answer is NO but the long answer is YES.
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Richo
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ABB motor and VFD selection

Post by Richo » Fri, 28 Aug 2009, 21:25

The CM1.5 probably best suits your controller.
Does 91kg 490mm Long and 250mm diameter sound good for your car?
I didn't see any list in the pdf for a CM1.7 they only go upto 5.

How about 11kW M3AA132MB 3GAA132003-JSC (J or H depending on gearbox bell housing)
This is still in a 132 frame 4-pole and weighs 59kg, 401.5mm Long, 264mm Dia.
Last edited by Richo on Fri, 28 Aug 2009, 11:42, edited 1 time in total.
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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Richo
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ABB motor and VFD selection

Post by Richo » Fri, 28 Aug 2009, 21:40

Or if you are into 2-pole since you are keeping the gearbox...
M3AA 132SB 3GAA131024-..C 7.5kW 2-pole Tm/Tn=5.2 56kg
M3AA 132SC 3GAA131003-..C 11kW 2-pole Tm/Tn=3.2 56kg
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!

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