Connecting a motor in triangle with inverters, Torque untill 87Hz

Originally posted by DickDV:

Using two different speeds to make tension is a ticket to trouble.

I hope not. We do this very regularly on paper and plastics web lines. Theoretically you can use this method with anything that can stretch. Practically you can only do this with materials whose percentage of elongation before ultimate failure is greater than the drive percent speed regulation. With modern closed loop FOC AC drives that is in the 0.001% class. Granted, you probably can't do this with steel. But draw control on carpet should be pretty easy. Carpet stretches like crazy, which is why installers can make it look so good.

Many people believe that any speed differential between two driven rolls will ultimately result in breaking a web between them. The thing many people forget is that the web coming into the zone hasn't been stretched yet. So each little sliver of web that comes into the zone between the two rolls will stretch and provide a percentage of it's length as additional material.

Now, in Combo's test case, where he is coupling two motor shafts together, you are correct. Since no new, unstretched material is entering the equation, sooner or later he will twist his coupling apart or, much more likely, the drives will go into torque limit and just operate there. But that is a completely different thing than running a web between two rolls.

Keith
 
rsdoran said:
If its a standard 9 lead motor it can be either Delta or Wye and be wired for high or low voltage...the motor is still either or but can be wired for high or low voltage.

Very True

But here in the UK which is standard spec for EU motors there are very few standard 3 phase units with 9 wire connection, most of the 9 wire motors are of american make or design. (These normally being NEMA framed)

Where on small motors (EU) Star is the Low voltage and Delta is the high voltage.

The 9 wire motors bring extra leads from the windings out, these leads are not bought out on EU/UK standard motors.

As Combo is in Brussels i would imagine he is using a 6 wire 3 phase motor and not a 9 but i may be wrong!
 
Brussels

Brussels is 50 kilometers from here ;-)


Okay,

6 wire 3 phase motor


Indeed KEITH,

We have allready applications where we do this kind of thing, and it works fine.

But, not with Micromasters, with Masterdrives Vector Control
 
kamenges, you and I are thinking the same way. As I said, the web must be capable of permanent stretch in order to use speed differential for tensioning.

A dry sheet of paper, a sheet of steel, or a sheet of fully formed plastic (not hot) will all fail to tension properly with speed differential. Sadly, I have tried and failed.

In the case of carpet which I have no exposure to, if it is as stretchy as you say, then Combo may be ok. When I watch a carpetlayer whack his knee against his stretcher, my impression is that carpet is pretty rigid. But, again, as you have said, with very small differentials, it may be ok.
 
Combo-

I took a quick look at the MM440. It looks to me like it would be capable of performing reasonably well winding in speed mode is you use sensorless vector control. I'm sure it will be able to do this if you add an encoder to the motor. If you have winders that operate in speed mode with the Masterdrive I would at least try the same thing with the MM440.


DickDV-
While I agree that doing sectional draw control or two drum winding with a steel strip might be a little tough (modulus is pretty high) paper and plastic are not that tough. We actually do an unwind/coater/rewind application in your neck of the woods. This machine has several intermediate sections that operate in draw control quite effectively. The machine runs paper in the 0.001" - 0.002" thick range at 3000 FPM. We have other machines that run plastics of various thicknesses the same way. With these materials if we went into plastic deformation as you state (ie permanent stretch) the material would be junk and the web lines wouldn't work. We keep the material in the elastic deformation region in the intermediate sections using draw settings. The product simply relaxes when we are done (if we don't rewind) or when the product is unwound (if we do rewind).

Keith
 
Const torque up to sqrt(3) x frequency

This trick is used to maintain constant torque output beyond the supply frequency.
e.g.
Motor: 230V/50 Hz (delta connection)
Inverter: Va=400 V @ fmax=400/230 x 50Hz = 87 Hz

The trick avoids the magnetic saturation that would happen by increasing the frequency (beyond the supply frequency 50/60 Hz) without increasing the voltage.

There some issues (like thermal load and noise) that need to be addressed especially if the motor is to have continue operation. The best you could do is to talk to the manufacturer of the motors and make sure that the service factor and the thermal classification are suitable for the job.

The following will have to be configure in the VFD (refer to above example):
motor voltage= 400 V
motor rpm= (120* freq(87Hz)/4) - slip

Regards,

LJAM
 
I got a little confused on this one and started rambling and just plain screwed up when I made that earlier post.

I have worked with paper and cloth that used multiple rollers/motors to unwind, stretch/tension and rewind. The systems can vary depending on many factors.

I am still confused on the thing about coupling the motors together...are they mechanically coupled DIRECTLY together?

OR are they coupled thru the material?

I am having trouble visuallizing 2 motors mechanically coupled that run at different speeds.

If possible can someone describe in more detail what is actually being done?

I am curious about the drives too, are they rated to use the 380vac? I have tried alot of tricks in my time but not sure it would be worthwhile to try this.
 
The motors are coupled together by the rewinding product rolls through the rollers they drive. I believe Combo's setup should look something like this:

[attachment]

Rolls 1 and 2 each have their own motors. Roll 1 is considered the speed master and runs basically at linespeed on it's surface. There is probably also some tension trim to that roll based on an upstream dancer or loadcell. Roll 2 runs at some percentage over Roll 1 speed. For example, Roll 2 may run at 0.5% over Roll 1 speed. The amount of 'draw' determines how hard the roll is when it is wound (how much 'inwound tension' it has).

Keith
 
yes

yes,

That BMP file is how our application is. :)


So (400/230)*50hz gives me 87Hz. That is something I needed to know


I have connected both motors in triangle (delta). My drives are 2 MM440's Micromasters 4kW's with and output of 400Volts max.
My motors are 2,2kW.
The drive (inverter) must allways have a greater rated power then the motors when doing that trick.

When I look on the Motor, I see that it can take 6,6Amps on 230Vols when it's connected in star.
It's is connected in Delta, BUT, todo the trick I parameterized the Drive for a 230Volts.

I also parameterized that it may take up to 150% current, that's 9,9Amps.
And I parameterized that the max frequency is 87Hz
And I parametrized the drives in vector control.

I tested, and when the motors run @ 50Hz, there is 230Volts on the windings. That's normal. When I load one motor very hard on 50Hz, 15Nm !!!, it takes 9,9Amps!

@ 87Hz I have 400 Volts on the windings.


Everything works I think
 
87Hz

To run a motor in 87Hz mode,you MUST select 87Hz!! configuring the drive for 60Hz then increasing the speed saturates the fields and torque roll off. By using the 87Hz setting, saturation doesn't occur to 87Hz where torque starts reducing. Anyone that doesn't know what differences between Star and Delta (or their proper names) should not mess around with this stuff. In a factory, overspeeding equipment will lead to premature failure and potentially a serious accident. The rating plates are there for a reason too. A lot of time and effort goes in to making sure the equipment is reliable up to the rpm setting for the particular mode. (I work in a CE and UL approval lab for a major manufacurer and have spent the last 4 months checking a new type of motor will run at the specified torque load, voltage load and current load without failure.
All motors are not run at 87Hz delta for good reasons. Low end torque is reduced for example so it is easier to start a compressor motor (high initial torque if there is pressure in the systemin star then switch over to delta, or run in star via a Variable Frequency Drive. In this compressor example an 87Hz delta configured motor will possibly stall and cook on power up.
 

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