AC motor 1st time running, strange vibrations

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Huub35
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Dear all,

It is a long time ago since I posted last over here. However, I was able to slowly make some steps in my conversion plan. Mainly buying a different VFD, and obtaining a 160 frame ABB dahlander motor with 15.5 Kw in 4-pole configuration.

Furthermore I worked on a simulator (if interested, just PM me), which enabled me to start looking for suitable conversion candidates.

Finally I kept on reading, both here (the source of my basic AC conversion scheme) and at the US friends of diyelectriccar. This has helped me to start first thoughts on the battery thing, most likely going for Headway now.

yesterday I managed to have my AC motor running for the first time. Although still on the grid, and just with standard parameters of my SJ300 Hitachi VFD, this was quite a nice moment.

However, I noticed that at low speeds (up to 2 Hz, but dominantly below 1 Hz), the motor was shaking quite noticable. This vibration has nothing to do with any mechanical unbalance, as it was not related to the rotational speed.

The motor (160 size frame, ca. 120 kg weight) was standing just on the concrete floor. No mounting, but also no elasticity, so the forces must be quite substantial.

Is this effect known or observed by someone? Can this be some internal movements of the coils?? What could be a resolution to counteract this? I am a bit concerned about this, as I want to avoid that I am internally destroying my motor.

At higher speeds (between 10-25 Hz), I noticed a higher pitch tone, seems also not related to the rpm. I assume this is the 6 kHz switching of the VFD, not that concerned about that right now.

On a positive note, I opened the motor (pretty easy with a AC motor), pictures will follow. I had purchased this motor, with Dahlander wiring, with the intention to get the internal star connection brought outside, and use this to go to a delta parallel switching, allowing higher base frequency.

I was very happy to discover that this internal star point did indeed exist (:-)), and that it was reasonably simple to reach. After some hacking on the resin soaked binding ribbons (please do wear safety goggles, that stuff is knife sharp!), I was able to free the connection, so now I am up to make a good connection to the outside, and start experimenting with the different switching opportunities.

Happy to hear your remarks and suggestions on the vibrations, regards,


Huub


PS. I have asked this same question at:
http://www.diyelectriccar.com/forums/sh ... post226805

I will try to combine answers from both side, so we keep aligned and learn together
Last edited by Huub35 on Sat, 12 Feb 2011, 18:14, edited 1 time in total.

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AC motor 1st time running, strange vibrations

Post by acmotor »

Just a quick response Huub...

The shudder at low RPM is likely caused by VFD settings.
If the magnetising level at low RPM is too high the emotor will behave like a stepping motor with a defined cogging as the VFD is stepping around the phases. No harm to the emotor although the torque ripple can presumably be harmful to a gearbox ?
This ripple is more noticeable with an unloaded motor that has little or no slip occuring as there is no torque on the shaft.

First thing is to do an automatic motor adaption (AMA or similar depending on the VFDs nomenclature). Next is to adjust parameters like " frequency for normal magnetising ", " start slip compensation " etc. All after nominating the desired torque mode typically " high constant torque " for EV application.

Re: 6kHz switching audible. Most VFD can select higher frequency (at the expense of some small increase in switching loss (few %), although the noise is not an issue in road EV. In fact it is quite the part as it is torque dependent. Maybe the new cool !
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Hi Acmotor,

thanks for these answers. Good to know that I will not do harm to my motor.

Next step is to reconfigure my motor (from parallel star to parallel delta, relatively easy now I have found the internal star connection of my Dahlander).

After that I will do the AMA, and see where I end up.

Is your experience that AMA produces more refined results compared to just do "4pole 50 Hz" settings at initial set-up?

Regaring the 6 kHz, that is the highest my VFD can run (AFAIK). We will see what will be the effect after AMA, as I noticed this hum disappeared above ca. 30 Hz.

Again, thanks a lot,


Huub

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AC motor 1st time running, strange vibrations

Post by coulomb »

Huub35 wrote: Next step is to reconfigure my motor (from parallel star to parallel delta, relatively easy now I have found the internal star connection of my Dahlander).

I question the wisdom of this in the DIYelectriccar version of this thread, starting a few posts after this:
http://www.diyelectriccar.com/forums/sh ... post226807
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AC motor 1st time running, strange vibrations

Post by coulomb »

These 230/460 V 6 terminal motors could be very useful in both direct drive and gearbox-retained conversions!

Please excuse me posting a clearer version of your diagram:

Image

From http://www.grittielettrotecnica.it/cata ... ase_uk.pdf.

I assume that we're talking about the lower pair of drawings.

Presumably, these can be switched from series to parallel with six changeover contactors like the left half of this:

Image
(Thanks Weber for this image, from viewtopic.php?t=585&p=13333#p13333.)

Oops, looks like that requires 9 wires to the motor. But surely with 6 changeover contactors, you can achieve the same thing with just 6 wires from the motor. In fact, 3 of the contactors could be single pole. I'll work on a diagram next.

For direct drive, the series/parallel changeover would be ideal, I think, giving 2x more torque at low speed.

For gearbox retained conversions, opening the motor to reveal the star point makes for an easy rewire to a useful 133 V @ 50 Hz wiring.

The only thing that bothers me is that they call this a Dahlander configuration, which to me implies funky pole-number switching to achieve one of the speeds at low torque and power. Or "high speed" might just mean applying 460 VAC in YY (high speed, parallel star) configuration. I haven't had a chance to read the PDF properly yet.

Huub35, do you know if the motor is specified at full power in both low and high speed configurations? Or surely it specifies the speeds in low and high speed configurations? Are they 1450 and 2900 RPM?
Last edited by coulomb on Sun, 13 Feb 2011, 13:39, edited 1 time in total.
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AC motor 1st time running, strange vibrations

Post by coulomb »

Oops. I get it. In parallel star, the windings are in the wrong direction, and so oppose each other. That's the penalty for the 6-wire connection.

So I'd say that in parallel star, the power is only about 1/3 of the power in series star.

Also, I think that this means that this motor can't be converted (or can it?) to parallel delta. The windings are designed for different voltages (probably about a 2:1 ratio), so paralleling them would mean that one winding will only get half power. So overall 3/4 of the power of series star (please correct me if I'm wrong there). It's probably better than series star, which I think will be only 1/3 power.

So what would be really useful would be a 9- or 12- terminal 230/460 V motor. Does anyone know if these are common?
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AC motor 1st time running, strange vibrations

Post by coulomb »

Then again, this page

http://www.eng-tips.com/viewthread.cfm? ... 661&page=1

talks about constant horsepower connections, so maybe some motors give the same power in both configurations. I'm confused as to how this is possible.

Huub35, any chance of a picture of the nameplate of your motor?
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AC motor 1st time running, strange vibrations

Post by weber »

Hi Huub,

I agree with others who say the low speed vibrations should go away when you (a) autotune the drive to the motor and (b) add an encoder and run closed loop. If you're going to have a fixed drive ratio you will need an encoder to get max torque at near-zero rpm.

But I would add that there may be some torque harmonics due to the Dahlander winding. I figure the winding has to be some kind of compromise between a 2-pole and a 4-pole-consequent and therefore not giving a good sinusoidal back-emf in either mode, and not giving as much power in either mode as a motor that was optimised for fixed 2-pole or fixed 4-pole. So for those reasons I wouldn't have recommended a Dahlander as a starting point for an EV.

But it is a clever way of ensuring you have all the winding ends available for that Holy Grail of rewiring from series star to parallel delta in a 4-pole and thereby getting a 3.5 times overvoltage without a rewind. So thanks for doing the experiment. Exciting stuff.

But you not only have to separate the 3 phases at the internal star point, you also have to separate the two windings of each phase at the 2U 2V and 2W points. Relative to the Dahlander 2-pole (high speed) connection, you have to reverse the direction of half the windings. Dahlander high speed is an inverse parallel connection. You need a proper parallel connection.

This is a pretty complex rewire. You're going to have to be very careful to label all the ends as you disconnect them, e.g. with different coloured electrical tape (one colour per phase) that you write numbers on for the four ends in each phase.

There are 12 ends and you only have 6 terminals so I suggest you permanently wire the two windings of each phase in parallel and make the terminals exactly like a standard (non-Dahlander) motor with the only options being star or delta.

That arrangement needs the phases offset by one in the second row of terminals so that delta can be wired with 3 parallel links. This adds to the complexity of the rewire.

I drew before and after diagrams on my whiteboard and took a photo when I finally got it right.

Image

I've only shown the rewiring of one phase. If I drew the others it would be a complete mess. Of course the other phases are the same only rotated 120 degrees.

So you could start by labelling the wires from the internal star point as 4U 4V and 4W, using a multimeter to check continuity from the terminal box to determine which is U V and W.

Then separate the wires going to the 2U 2V and 2W terminals and label the ones that have continuity to the 1U 1V and 1W terminals as 2U 2V and 2W. The ones that have continuity with the old star-point wires should be labelled 3U 3V and 3W.

The "1" wires stay on the "1" terminals and the "2" wires stay on the "2" terminals but not on the same "2" terminals. They have to shift one terminal to the right and the "2" terminals have to be relabelled from "2U 2V 2W to "2W 2U 2V".

All the "3" wires (that used to go to the "2" terminals) now have to go to the "1" terminals.

All the "4" wires (that used to go to the internal star point) now have to go to the "2" terminals (don't forget about the shift right).

Then meter to check that the phases all go diagonally and none are connected to each other. Corresponding to this.

Image
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AC motor 1st time running, strange vibrations

Post by weber »

Oh darn. I still didn't get that Dahlanderconversion right. It's more complicated than I thought. I forgot the the designations 2U and 2W are swapped, presumably so that there is only a 30 degree phase discontinuity on switching between Dahlander speeds.

It will take me some hours to get back to it. Please ignore in the meantime
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AC motor 1st time running, strange vibrations

Post by coulomb »

weber wrote: But it is a clever way of ensuring you have all the winding ends available for that Holy Grail of rewiring from series star to parallel delta in a 4-pole and thereby getting a 3.5 times overvoltage without a rewind.

Can I be clear on this point, please? Will Huub end up with a motor that isn't "Dahlander crippled"?

Presumably there will be a small performance hit from the fact of the compromise in back-emf... or will this actually go away? From your whiteboard diagram, it might actually be a normal winding distribution.

In the series star configuration, do the windings drop about the same voltage across them? Or is one set of windings wound with fewer turns? I'm trying to decide if after all this rewiring, the motor is more or less as capable as a motor purposely designed for 133 V running (in delta, or 230 V in star)?

If it's not crippled, then this may in fact be the holy grail of "easy" rewiring. (Just as soon as you sort out the correct rewiring... thanks in advance!)
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AC motor 1st time running, strange vibrations

Post by coulomb »

I would point out that this holy grail motor gives the user the choice of either a 2x over-frequency configuration (non-inverse parallel star), or a 3.5x (really 2√3x) (non-inverse parallel delta). These are selectable with links the same way a standard 6-terminal motor with three windings can be connected in either star or delta.

So in effect, the internal rewiring that you would do does a 2x over-frequency modification, and if the original motor was in star, you have the choice of an additional √3 over-frequency factor.

I don't know if these motors can come originally in delta; if so, you would end up with a choice of 2/√3 (1.15x) and 2x.

It turns out that Huub35 wants a 2x over-frequency modification, since any more would be wasted by his controller's current limit.
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AC motor 1st time running, strange vibrations

Post by woody »

Seeing the nameplate will be good to work out if it's Fan Dahlander, or CT.

Are there already 2 wires coming to 3 of the six terminals?

That would be the midpoint of each phase.

You'll need to find them to make it parallel.

If they don't come out to the terminal box they would be internal and look like the internal star junction - it's possible you've found one of them rather than the star?
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AC motor 1st time running, strange vibrations

Post by weber »

I can't fix my diagram and rewiring method until I know how your motor is currently wired at the terminals. With the internal star point separated, can you meter the terminals to determine whether they are wired like this,

Image

or like this,

Image

or something entirely different?

Good points Woody.
Last edited by weber on Sun, 13 Feb 2011, 17:45, edited 1 time in total.
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AC motor 1st time running, strange vibrations

Post by Huub35 »

Dear all,

thanks a lot to all of you for thinking with me, the time shift is meaning I cannot react immedately, sorry for that.

It is a 4/8 pole Dahlander, with 15.5 kW for high speed (1460 rpm at 400V 50 Hz) and 2.7 kW for low speed (730 rpm at 400 V 50 Hz).

I would love to post a picture of the nameplate, but somehow I am not able to connect that to this post. Can someone give me a hint how to do this properly.

I have to jump of now to family, will try to work on uploading the picture when I come back.

Again, thanks a lot for helping me in this matter,


Huub

Edit, nameplate upload successful:
Image

edit edit:
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
Last edited by Huub35 on Mon, 14 Feb 2011, 01:01, edited 1 time in total.

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AC motor 1st time running, strange vibrations

Post by Huub35 »

Dear all,

I have tried to make a picture of my intentions:

Image

I have used the same notation as in the Dahlander picture above, and added "A","B","C" for the three joints of the internal star connection.

I am pretty sure I have found this point, as the discovered joint is connecting three different coilsets, and not connected to any of the leads to the junction box.

My plan is to open up this internal connection, and wire "A" to "1U", "B" to "1W" and "C" to "1V". This seems to be a pretty simple operation, I should only pay attention to proper fixation and isolation.

Then I would connect the three pairs of windings in delta (would then be a sort of parallel delta I think), giving a sqrt(3) reduction in voltage/increase in speed (I hope :-)).

Is this a correct assumption, or did I miss something here?

[edit: Weber, I see I am basically doing a similar thing as your whiteboard picture (my "A","B","C" are your 4U, 4V, 4W (in another order)), only I am not reversing one of the parallel windings so I do not split at the middle joints (2U, 2V, 2W). I was assuming that as the parallel windings work correctly in the high speed star connection, they would also be oriented right in my modified delta scheme, so no need to reverse one coil. What would be a smart way of finding this out, without trial and error?]

Regards,

Huub
Last edited by Huub35 on Mon, 14 Feb 2011, 02:17, edited 1 time in total.

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AC motor 1st time running, strange vibrations

Post by coulomb »

I've realised that there will be no 2.√3 change in frequency/voltage. In the parallel star form, this motor is still a 400 V motor (not 460 V as I was assuming; the controller is capable of 460 V). So the windings are all designed for 230 V.

In series star mode, each winding only gets half the voltage it would in parallel star mode, and twice the current. With the extra pole, it won't need more than half the usual voltage for the same V/Hz ratio.

The other thing I got wrong is that I assumed that the parallel star mode is the weak one with the windings opposing each other. However, the high speed mode is the high power mode on this motor (and probably all Dahlanders, both the fan variety and the constant torque (CT) variety).

So what Huub is suggesting is merely a star to delta change from the parallel star arrangement. That's a factor of 1.73x; there is another factor of 460/400 = 1.15x from the voltage of his inverter compared to the nominal voltage of his motor. Together, there is a 1.99x change, which he was calling a 2x for brevity. This became confused with 460/230 dual voltage motors; not the same thing as Dahlander motors (dual speed).

So no holy grail here for people looking for 3.5x over-frequency with simple rewiring.

So Huub: I don't see anything wrong with your intentions; we just misunderstood them.

I would still take Weber's advice, and bring out each pair of windings, permanently paralleled, to six terminals, so that you can still do the standard delta or star wiring. You may find that you need star wiring for increased low speed torque. You could drive it for a while in star mode, while you figure out how to do star/delta switching on the fly. It has been done before with an industrial controller; not your exact controller, but it should be doable.
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AC motor 1st time running, strange vibrations

Post by coulomb »

coulomb wrote: So Huub: I don't see anything wrong with your intentions; we just misunderstood them.

One thing I'm still not certain about is whether the motor will have comparable power to a motor designed for 400 V 4 pole, and whether there will be additional torque ripple (compared to a single speed motor) as a result of the compromise in winding placement that is needed for Dahlander motors. Perhaps with the two windings in (non-inverse) parallel, it becomes a standard 4-pole motor.

Did you choose this motor because it was available for use, or did you deliberately choose a Dahlander? I can't see any advantages to the Dahlander, as you are using it. But I've been wrong on everything else so far Image
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Post by coulomb »

Oops! I was being lazy.

You asked about this motor here: Two speed motor, modifiable/useful for EV?.

My understanding is that ABB motors can be ordered with the "S" option (i.e. use in Star mode to connect to ~400 V). Perhaps you liked the fact that it was designed for 400 V rather than 415 or 400-440?

Or did you find it hard to order "S" options for other motors?

Just curious.
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AC motor 1st time running, strange vibrations

Post by Johny »

Hi Huub
I had some serious motor shaking when I first ran my complete installed setup in Vector mode. It was fine in v/f mode.
Auto-ID helped but the motor still wanted to jump out of the car at 400 RPM.
I was about to start playing with the loop gain and time constants (as per the manual) when I noticed that my VFD zeroed all of these parameters when a shaft encoder was enabled.

Since I had a shaft encoder already fitted (600 PPR) I wired it up and enabled it with perfectly stability as the result.
I still have to run it under load but it looks encouraging.

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AC motor 1st time running, strange vibrations

Post by markrmarkr »

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.

What I don't understand is how you plan to tune your controller (AMA) for both configurations.   Are you planning to use two controllers?   Or can your controller store and, on the fly, switch between the two configurations?

cheers,
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AC motor 1st time running, strange vibrations

Post by coulomb »

markrmarkr wrote: You want to have sort of an electric gear change by switching between delta and star/parrallel and series.
Huub would prefer no switch at all, but may require one from star to delta to get enough low speed torque.
What I don't understand is how you plan to tune your controller (AMA) for both configurations.   Are you planning to use two controllers?   Or can your controller store and, on the fly, switch between the two configurations?

We were planning to use star/delta switching on the fly, as was demonstrated by Ross Pink years ago in his Van. You save two sets of configurations in the controller, and one command lets you make one or the other set active (from memory).

There is also a "flying start" command that alerts the controller to the fact that the motor may be spinning, so don't assume it's not.

I emailed Tritium_James about the series/parallel switching they do on the Civic. They had it working, but water got into the switchbox and it's currently disabled. The Civic's motor has basically the same inductance in series or parallel, since the inductance of the actual windings is so small, and they use external inductors. So there is no parameter set switching needed for that motor. However, it should be possible to switch parameter sets on the fly (as would be needed for induction motors). This is currently untested.

The WaveSculptor apparently needs no "flying start" command, as it always checks the encoder for the motor position and speed.
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Post by woody »

Another Dahlander image, from page 3 of http://www.tlt.de/dateien/173.pdf which I had previously downloaded.

Image
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AC motor 1st time running, strange vibrations

Post by Huub35 »

coulomb wrote: Oops! I was being lazy.

You asked about this motor here: Two speed motor, modifiable/useful for EV?.

My understanding is that ABB motors can be ordered with the "S" option (i.e. use in Star mode to connect to ~400 V). Perhaps you liked the fact that it was designed for 400 V rather than 415 or 400-440?

Or did you find it hard to order "S" options for other motors?

Just curious.


Coulomb,

the three reasons for taking this motor:
1) it was very cheap (50 EUR)
2) it would give me something to experiment with, with a chance of succes of getting the car driving
3) the ABB motors, and esp. the "S" option, is much more expensive over here unfortunately

Regards,


Huub

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woody
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AC motor 1st time running, strange vibrations

Post by woody »

(I retract my previous late night statement that dahlanders switch star/delta)
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
Bringing out 12 wires will get you other possibilities:
230/400/460/800V @ 50Hz
4/8 pole
All 15kW

The nicest for EV - the 230V 15kW 4 pole which gives you full torque to ~2250 rpm at 400V
800V 15kW 8 pole should let you have heaps of torque very low down (<350rpm)


230V 4 pole 15kW delta parallel
800V 4 pole 15kW series star
230V 8 pole 15kW
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AC motor 1st time running, strange vibrations

Post by coulomb »

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.
800V 15kW 8 pole should let you have heaps of torque very low down (<350rpm)
Well, maybe the "constant torque" variety... oh wait. If they really are constant torque, then they're not much use; just lower speed.

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.

Ok, here is Huub's Fan drive Dahlander:

Image
(from this post).

This is the similar motor (same frame size and weight) in the constant torque variety:

Image

Ok, I've just proved myself wrong Image

However, although the "constant torque" version has more torque in 8-pole mode than in 4, there is more torque again in the "fan drive" version in 4 pole mode.
Last edited by coulomb on Mon, 14 Feb 2011, 17:00, edited 1 time in total.
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