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AC motor 1st time running, strange vibrations

AC, DC, amps, volts and kilowatt. It's all discussed in here
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woody
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AC motor 1st time running, strange vibrations

Post by woody »

coulomb wrote:
woody wrote: My take:
Fan Dahlander 4/8 pole:
High speed/power - you have a 400V star (parallel) 4 pole 15kW
Low speed/power is an 8 pole 800V 15kW - which only produces 4kW at 400V
But the nameplate says 2.7 kW. Dahlanders in low power mode, especially the Fan variety (I don't pretend to understand the difference) have very low power output.
The extra poles are consequent, not real; I don't see how you get more torque in 8-pole mode than in 4-pole mode. But please, prove me wrong.
[/quote]

I was just thinking the amps/Nm would be much lower, so you can torque boost it with fewer amps.

But the magnetic field of the 8 poles goes somewhere, even if there isn't a set of coils driving it...
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Huub35
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Dear all,

thanks a lot for all these responses. Related to this I have two questions:
- what is exactly "concequent poles"?
- looking back at the analysis of weber, I see I am planning more or less the same, however not inverting half of the windings as he had planned. Would it be possible to conclude what is the correct way without trail and error, or can this only be resolved through experiment?

I will try to make some more pictures the next time, and also keep you updated on the outcome of all. This is certainly an interesting challenge.

Regards,


Huub

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weber
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AC motor 1st time running, strange vibrations

Post by weber »

Hi Huub,

Sorry I have taken so long to get back to this. My diagrams and suggestions are completely irrelevant to your case because I had assumed your Dahlander was a 2/4 pole rather than a 4/8 pole. Since it would be too slow for direct drive as an 8 pole I agree that what you propose is the best option. You do not need to separate anything but the internal star point, and you would put the windings in inverse-parallel and rearange them from star to delta to get that sqrt(3) voltage change.

I am still interested in how the windings are mapped to the terminals currently, as I have seen two contradictory rotations given in diagrams on the web. In one case the second row is offset by one but has the same rotation. In the other the second row actually has the opposite rotation. I figure one of these has to be wrong.
Last edited by weber on Tue, 15 Feb 2011, 17:10, edited 1 time in total.
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weber
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AC motor 1st time running, strange vibrations

Post by weber »

I should have said you will keep the windings in inverse parallel, i.e. not invert them from the way they were, as I was showing.

Consequent poles are just as real as wound poles. It's just that there is no winding actually looping around them. They occur in between two neighbouring (looped) windings when those two windings have the same polarity. If two neighbouring windings (on the same phase) have a gap between them, and they are wired so they both produce north poles at a given time, then a south pole must form between them at that time, as a consequence of the two neighbouring norths. Hence "consequent" poles.

So your motor has 4 wound poles in each phase. When these are wired so as to alternate N S N S then it functions as a 4 pole motor. When these are wired so they are all the same, e.g. N N N N, then the consequence is that the opposite poles will form between them, giving NSNSNSNS and it functions as an 8 pole motor.
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Hi Weber,

thanks for explaining this, very clear, and also clear now why a 8-pole dahlander is not as efficient as a true 8-pole.

I will note down the leads in the connection box. For normal Dahlander usage it is not so important, as the leads of the second row are either shorted or connected to the VFD. something like a delta wiring (with busbars from first to second row) do not exist in normal Dahlander usage.

Also good to have your blessing Image for my modification star to delta. I will report my findings.

Regards,


Huub

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AC motor 1st time running, strange vibrations

Post by Richo »

markrmarkr wrote: I think I understand what what your trying to do Hub. You want to have sort of an electric gear change by switching between delta and star/parrallel and series.


I agree but I think the real question is it worth it?
ABB wrote: from the ABB catalog, it is a Fan Drive Dahlander, this type:
15.5/2.7kW Type M3AP 160 L, 3GAA 168 305-ADA, 1460/735rpm, efficiency 88.5/79.5%, 0.85/0.51 cos(phi), 30/9.5 A, 101/35 Nm, 2.6/2.6 Tb/Tn, 125 kg
How would this motor compare to a standard 4-pole 15.5kW 160 frame with 90+% efficiency and Tm/Tn>=3.5
I'm skeptical Image
Do you expect to get more than a regular motor in a standard system?
So the short answer is NO but the long answer is YES.
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AC motor 1st time running, strange vibrations

Post by woody »

Richo wrote: Do you expect to get more than a regular motor in a standard system?
I think he expects to get better value for money by rewiring a 50 euro motor to almost match a 1500 Euro 15kW 400V Star motor. :-)
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AC motor 1st time running, strange vibrations

Post by weber »

Huub35 wrote:I will note down the leads in the connection box. For normal Dahlander usage it is not so important, as the leads of the second row are either shorted or connected to the VFD. something like a delta wiring (with busbars from first to second row) do not exist in normal Dahlander usage.

The way in which it matters very much for normal Dahlander usage is when contactors are used to switch speeds on the fly. You always switch a given line from the top row to the same position in the bottom row. If the windings are not arranged correctly the back-emf could find itself suddenly 120 degrees out of phase with all the lines, or worse, trying to turn the motor in the opposite direction. In either case there will be an almighty thump and hopefully only some tripped circuit breakers.

So I'm curious as to which of the contradictory diagrams tells the truth.
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Hi Weber,

I see, I will get the current mounting of the leads.

Regards,


Huub

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AC motor 1st time running, strange vibrations

Post by Huub35 »

woody wrote:
Richo wrote: Do you expect to get more than a regular motor in a standard system?
I think he expects to get better value for money by rewiring a 50 euro motor to almost match a 1500 Euro 15kW 400V Star motor. :-)


Woody,

well, in fact, it is more or less a 2500 EUR motor that I am trying to copy (or even more, I never went above the 132 frame when asking a quote).

I indeed fear I will not achieve the performance of a real 4 pole motor, but I hope to achieve at least a drivable situation.

If not, I might be able to do a rewind and then get decent performance.

On that last idea, does someone know whether the iron package and rotors for motors of a same frame size are the same, or whether this is different for a 2/4/6/8/dahlander/etc motor? This would be interesting to know to see what I potentially could achieve.

I will take some pictures of the innards the next time the motor is opened.

Regards,


Huub

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AC motor 1st time running, strange vibrations

Post by Richo »

Ah so cost is the driving factor - no pun intended Image
Some of the motors 160+ can get quite pricey esp in alloy.
So picking up somthing similar for much less is always good

I would think the rotor would be the same as eqv 4-pole motor of the same brand and series.
It's possible the stator iron is the same too.
It may be slightly modified to give some marginal improvement.
I can't see why it couldn't be rewound later to a stock 4 pole.
It may work out being a bit more than 15.5kW in 4-pole (ie 18.5kW)

Pics are always good Image
So the short answer is NO but the long answer is YES.
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Dear all,

time for a bit of update, today I did my next step on the modified Dahlander, with some plusses and minusses, but let's take it step by step.

First an answer to Weber, regarding the connection of the wiring. I measured the coils after I broke the internal star point -> the connection is like the second picture in your message, with the outer connections crossing, and the middle one just passing straight.

Step 1: I opened the motor again, and tried to open the internal star point. Is seemed to be soldered, but even with a gas burner, no sign of melting, so I decided to cut it off. I hope I am not going to regret this step.

Step 2: connecting new leads to the opened windings. I checked with a DMM, and indeed the wiring was as we thought. It is pretty tough getting a proper reading on the DMM though, and I still have the feeling not all resistance values were the same.

Step 3: connecting the leads together (switching two original leads to come to the standard mounting order instead of the crossed over Dahlander order). Furthermore building three short bus bars to get to delta mode. We used flattenend copper pipe for this, works quite well for our current purpose.

Step 4: connecting to the VFD, and starting up -> it works !!

Step 5: but .... it makes much more noise, and squeeching tones. Even up to 50 Hz is is still screaming a bit. I will upload a movie to youtube, so you can judge for yourself.

Step 6: so, listening to your advices, I decided to start an AMA. However, this has not been succesful. During the Sensorless vector control phase of AMA, somehow the current became such that the house fuses did not cope anymore.

Step 7: tried to do SLV with some approximate motor parameters, however, the motor then makes a big jump and goes into error mode, so not succesful

Step 8: again doing AMA, now it got further, and also in the movement area some progress, instead of just vibrations, the motor walked about one meter :-(, very scary.

So after this, and some more blown fuses, I have decided to call it a day.

The issue I have can have many reasons as I see it now:
- some connections that I have made are not correct, so the current is not equal
- the windings are not meant to be used like I use them (for your information, I have 36 slots for the stator windings, if that is helpful for someone)
- The starting values of AMA (base freq, power level, motor voltage, ..) are not good to come to a proper autotuning

Also I noticed that the motor was a bit warm (hand warm), which is strange, considering that no power was demanded from the motor. Or is that normal during an AMA session?

I have thought that I should make one step backwards, and go to the original wiring again (very simple now with the external leads to the star point). THen do an AMA again and see how that works.

If that is going well, then at least it seems that my new connections are sort of OK (they are temporary, but should still be proper for safety and performance testing).

From there I was thinking that I take the parameters from that AMA,and do the conversion from parallel star to parallel delta numerically, entering these values by hand in the VFD. And the do a run-up again (and pray :-)).

On a lighter note, I noticed that my VFD is not a SJ300-550 (55 kW nominal) but a SJ300-750 (75 kW nominal)!! THat is somehow a miracle, as I paid for a 550, but I will not complain I think.

I will put some pictures here tomorrow, when I have found the cable of the camera.

Regards,


Huub

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