Why two induction motors don't run at exact speed

Hi ganutenator,

They're not mechanically linked. They're placed in a very close proximity, withing millimeters, for the product to transfer from on to the other and it is at the point of transfer that the product twists if the speed of on is faster than the other.

Thanks
Kal
 
you don't need to use the custom line shaft software
just set both A1000's as closed loop vector control
use the pulse out from the master VFD to the Slave pulse input
the software is very expensive in case of a conveyor it'd over kill
Line shaft software is for printing units or shear type on configuration
in fact you may not even need an encoder depending on how tight you need.
 
you don't need to use the custom line shaft software
just set both A1000's as closed loop vector control
use the pulse out from the master VFD to the Slave pulse input
the software is very expensive in case of a conveyor it'd over kill
Line shaft software is for printing units or shear type on configuration
in fact you may not even need an encoder depending on how tight you need.

Thanks Gary, the price was high then shocking when I had it repriced for single phase 230 input as they resized the drive from 1HP to 5HP :mad:

I will reprice it without ELS and compare.

Much appreciated.
Kal
 
kalabdel, cumulative error is most often a problem when your system involves tensioning a web, as in a paper sheet, plastic sheet, or even a metal sheet. For example, if the error, however miniscule, is always negative, that would eventually accumulate enough for the sheet tension to go slack. On the other hand, if it were always positive, the tension would gradually increase until a sheet break or roll slippage would occur.

The benefit of an encoder speed feedback system, usually called "closed loop" is that, if a pulse or more is missing on one revolution, it will be made up on the next revolution. That way, the error always sums to zero over time due to both positive and negative error swings.

Cumulative error also can be a problem when you are trying to coordinate the position of one part of a process to another part. For example, if you are trying to imprint something on a paper sheet that already has printing on it, it is essential that the new impression be made in the same place on the sheet image. Cumulative error would permit the added impression to slowly "walk off" the sheet image. Clearly not acceptable!
 
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Thanks Gary, the price was high then shocking when I had it repriced for single phase 230 input as they resized the drive from 1HP to 5HP :mad:

I will reprice it without ELS and compare.

Much appreciated.
Kal

I would look at the true servo solution if keeping two axes in sync is so critical. If going with Yaskawa, then check Sigma series, they do have drives and motors in that power range (5 HP = 4 kW), but it HAS to be three-phase power supply.

Won't be the cheapest. But it will be able to synchronize with very high degree of accuracy.
 
"Each has functionality for Master/Slave. "
This is not the best way to run two motors synchronously if you are controlling both of them. They should both be geared to the same virtual master.


Pulling an old thread for more information. What does "geared to the same virtual master mean"?


Thanks
 
What kind of conveyor speeds you running at?
I know that some types of open loop control vfd settings and drives, don't work too well at fast speeds (aka speeds aren't accurate).
 
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I pulled the thread to review as I have something similar coming up but for the sake of furthering the discussion I will describe the old setup that I was dealing with.


Scenario:

Two machines from two different suppliers with separate controllers, drives and motors. Each has a conveyor with 1KW motor it it controls its speed via 0-10V analog signal.
The conveyors are placed at very close proximity, we're talking millimeters so that the product (plant of some sort, say onions) is transferred from one conveyor to the next. The first machine cuts them in in someway and the next sorts and bunches them.
The speed of the first conveyor changes based on how fast the product is being put on the conveyor by workers it goes from a complete stop to 50Hz. and we'll assume the second runs all the time at the same speed.

If the speed vary even slightly the plant twists as it is transferred from on conveyor to the next one and that causes problem as it is sometimes slips out of the belting that picks it up for sorting.



Which bring me back to Peter's comment "This is not the best way to run two motors synchronously if you are controlling both of them. They should both be geared to the same virtual master.". What does "should be geared to the same virtual master" mean?
 
Pulling an old thread for more information. What does "geared to the same virtual master mean"?


Thanks

There are the physical positions of the real axes and the ideal position of the virtual master. I NEVER recommend gearing one physical axis to another the motion controller does not have control of the master.

Most industry standard controllers have a target generator that generates position for a virtual master. The target generator generates perfect position, velocity and acceleration for the physical axes to follow. This has TWO purposes.
1. The target velocity, acceleration and jerk can be used to generate feed forwards. Feed forwards reduce the following error.
2. If physical axes do have following error there is a good chance that both axes will lag behind by the same amount so that the error between the physical axes is small.
 
Thanks Peter.
This thread is a great example of why I'm glad we don't lock old posts, even if it means we need to deal with accidental zombies sometimes.

Dredge up an old thread, ask a pertinent question, get a pertinent answer. Don't have to make a new thread referencing the old thread, which just complicates things.

Hi5's all around 🍺
 

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