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

I aint giving up

Can you state more details please.
What is the supply voltage?
Is this a WYE (Star) or Delta (triangle) connected motor?
 
Ron,

Most small motors are wired for:

Delta 220v 50 Hz

Star 380v 50 Hz

Consider only the Delta case. Normally it would be connected to a 220v Three Phase supply and draw say 5 Amps at 50 Hz.

If we used a VSD connected to the same 220v supply then it would usually be set up with a Base Voltage of 220v and 50Hz, giving a V/Hz ratio of 4.4. When the drive varies the frequency it also varies the voltage to keep this ratio constant and thus the motor field, torque and current constant. In this case the Maximum voltage the drive can output is limited to 220v.

If we now connect the same drive to 380v, three phase the maximum output voltage is now 380v. If we set the Base Voltage to 380v and the Base Freq to 87Hz then the Volts/Hz ratio is still the same ie 4.4, BUT now the drive can run up to 87Hz and still maintain constant field, torque and current.

It all seems counterintuitive at first but truly this is a simple technique that works well.
 
Hi

Hey,

Thanks, that's what I wanned to know.

Can u also explain with simple formulas how u get 87Hz ?

And 400 Volts on a Coil that is ment to work with 230Volts (Delta), Isn't that dangerous for the coils ?


Great thanks,


Machnically coupled:

I will try to explain that. On Motor rotates at a speed in Hz, givin in a variable on an Operator Panel. And the other Motor needs to rotate faster. We are a factory that makes carpets. It's is ment to reroll a carpet. 2 rollerheads needs to rol a carpet. With the difference in speed u get tension on the rol. That's the function of it. U can give the tension in a variable on the Operator Panel.
mechanically coupled with carpet.

But, in my test, I coupled 2 AC 3 phase motors directly on each other, yes, directly :)
 
I would have to see 2 motors mechanically coupled to each other that could accomplish this. It doesnt make sense.

Most small motors are wired for:

Delta 220v 50 Hz

Star 380v 50 Hz
Not sure I agree with that. 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. Wye/Delta start is used for some motors but it isnt meant to run any motor on WYE when its DELTA run.
http://www.patchn.com/motor_connections.htm
 
Power = I x E

DAN:

You have published secret telephone company proprietory information,
Power = I x E
, I would not be surprised to find out that the US government has it classified also.

One of the police radio techs wrote it on a piece of paper one day tring to figure something out, and a passing tlephone guy saw it and started ranting and raving like a lunatic about stealing proprietory telco information, and he was going to call a cop. At the time, the other radio tech and I were in full uniform complete with police patches, in a room with several uniformed officers. We all had a good laugh while the telco jocked went to a phone to call his supervisor.



REF: TRIANGLE

Perhaps that is how the translator option trnslates it.

regards.....casey
 
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And 400 Volts on a Coil that is ment to work with 230Volts (Delta), Isn't that dangerous for the coils ?

Yes this technique does increase the voltage on the motor windings. All modern motor insulation is rated to handle at least 3 times the nominal operating voltage so normally there is no problem.

Of course it would pay to check the ratings for your motors and make your own judgement.
 
I think what you are looking for is a torque following application which I am sure you can't do with the MM . You can probably botch something up with connecting up a motor low voltage to a high voltage supply and playing with drive parameters until you get something . I would have thought that you would wanted a setpoint over digital rather than wobbly old analogue , it is hardly going to be very precise .
 
It sounds to me like Combo is working with a 2-drum surface winder for carpet. So while the rolls are mechanically coupled the coupling is VERY compliant. By changing the speed relationship between the two rolls you change the amount of in-wound tension in the roll without affecting upstream process tension.

I think you can approach this one of two ways. I believe the more standard way is to vary the speed ratio between the two drums. For example, your farther downstream roll would run 0.5% faster than your upsream roll (the 0.5% is an arbitrary number as an example). If you use an analog output sending out drive torque command from your two drives you can get some idea of how much tension you are winding in.

The second method would be to give the second (downstream) roll a high fixed ratio and then use a second analog input on the second drive as a torque limit. This would let you adjust inwound tension by varying the torque limit.

I think the first method will give you more consistent results. You can actually calculate your inwound tension using the material modulus of elasticity, it's cross-sectional dimensions and ratio between rolls. The speed ratio idea also ignores any system friction that could cause inconsistency with the torque method.

If this really is a two-drum winder application it is not something you can simulate by coupling two motors directly together unless you use the torque limit method. The speed ratio method counts on having an 'infinite' supply of material to stretch. A coupling has a very finite amount of stretch.

Keith
 
Reply

It sounds to me like Combo is working with a 2-drum surface winder for carpet. So while the rolls are mechanically coupled the coupling is VERY compliant. By changing the speed relationship between the two rolls you change the amount of in-wound tension in the roll without affecting upstream process tension.


That is exacly what I mean.


I have a S7-300 and 2 MM440's connected on profibus. The Amount of tension can be given on an Operating Panel, this one connected on the MPI port of the PLC.
Also u can set a windspeed.

one motor wil turn windspeed and the other one windspeed + tensionspeed


That's how it works.


It's the first time that we connected the DC-Link of the Micromasters also. We never have an application where we done this. This should be an application where it is possible.
So that's one
And the motors turn a different speed. How more tensionspeed u set, how more defference in speed, how more torque positieve for one drive and negative for the other.
Tot test these last to things I had to couple 2 motors directly.
The trick with delta and constant current and torque untill 87Hz, that's necessary because, it has to be possible to wind faster then 60 Hz.

but, when u wind a carpet, when of the 2 blocks, the torque shoot decrease; can I do that wit current limitation ?
What's the formula of Torque (with the use of current in it)

greetz

ans great thanks
 
The application is a little more clear now -
Yes , this is a good case for connecting the bus together obviously the second stretch roller will run at a negative torque and hence regen relative to the winder .
Obviously the winder will be the torque master , and the second will be the follower , but the second drive will be the speed master . You'll have to have a diameter from the winder so that torque compensation and speed compensation can be carried out ?
I suppose the other way is to use a "bouncing bomb" roller between the two drives which is weighted and position sensed , this would also give you constant stretch .
 
Originally posted by Fred Floggle:

You'll have to have a diameter from the winder so that torque compensation and speed compensation can be carried out?

This is a surface winder so the winding drum speed isn't influenced by diameter, as is the case with a center winder. So speed compensation based on diameter isn't an issue. A case could be made that you want to modify the drive velocity loop gains as the diameter builds. However, I wouldn't get into that unless it's absolutely necessary. it's not that it's particularly difficult. It's just that it often isn't necessary.

Originally posted by Combo:

but, when u wind a carpet, when of the 2 blocks, the torque shoot decrease; can I do that wit current limitation ?
What's the formula of Torque (with the use of current in it)

You really want to modify the torque limit in the second drive, not the actual current limit. If the MM440 is operating in closed loop vector mode this should be possible. Using current limit in an AC drive to control torque with any accuracy can be a little tough.
However, I still think you want to go with a full velocity system. If you go with a torque based system you need to know how much torque is being used just to overcome friction and inertia losses in order to figure out how much torque you need to tensioning. The only way this will work with any accuracy is if you are sure the 'system' losses (friction) are MUCH less than the required tension torque.

If it is a typical two-drum winder, the first roll the material contacts sets the base winder speed and may be tweaked based on tension feedback from upstream. The second, farther downstream, roll runs at some ratio (or percent draw) to the first. This draw sets the amount of web stretch as the roll is wound, which is what determines the inwound tension and, ultimately, roll hardness.

If you really want to go the torque route you will need to look up how to map a torque limnit value from your plc into the approporiate torque limit of your second roll drive. You probably also want to read back both the roll drives actual torque values.

Hope this helps.
Keith
 
Quite interesting (if carpet can be) - I didn't know that there were different methods (though I should have guessed it ) . If my thinking is correct , then you stretch between two rollers a known amount ,winding onto the finished roll , and rely on shrinkback to provide the roll hardness .
I have commisioned a viscose fibre spinning and cutting project where there were 6 stretch rollers 600mm in diameter , the first of these was the speed reference , and the second was the torque master with the others following with equal torque , but speed offset as required to give the necessary stretch , also calculations for shrink before the cutting unit .
All drives used were RA GV3000's over controlnet , calculations in CLX . Some clever stuff employed , common DC bus for all drives to allow for the reuse of regen energy .
 
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hey

Wel, I've allready done some tests, and I didn't use vector control but FCC. No Torque regulating, but only 2 different speeds. What I see, is indeed, when one drive runs 50Hz and the Other 54Hz, that the Torque of both drives is increased. And one Torque is positieve and the other value is negatieve.

Maybe I don't need to limit the torque..., BUUUUT,

I'm gone test Vector Control right now,

Thanks for all the reply's, it's really a big help !!!!

And sorry for my poor english typing, reading and typing, it's quite a difference, but I'm inproving (I think)
 
Using two different speeds to make tension is a ticket to trouble. No matter how small the difference, tension keeps increasing until either the web breaks or one of the drives fault on current limit.

The only time I've seen this work is when the web can have some permanent stretch.
 

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