Belt conveyor control 2

[Masbibe]

Hi guys,

I am interesting what is your opinion which is the optimal method for controling motors on belt conveyor in open pit minning.
Motors are supplied via VFD with possibility of speed or torque control (ABB ACS800). Belt distance between 2 driven drums are something about 20-30m. Belt is made of some rubber material with small iron bars inside.
In attach you can find simplified picture of belt conveyor. Picture is not exactly same as on reel belt conveyor, there is few more nondriven drums for changing belt direction. This is just for visualisation.
So question is should there be:
1) 1 master and 3 pure torque followers
2) 1 master and 3 torque followers with some kind of window control (how much should be window)
3) 2 master (one on each drum) and 2 followers, is there any "connections" in that case between this 2 masters (or something like drooping etc.)
4) 4 torque controlled drives with speed regulator in PLC (with window control of drives)
5) something not mentioned above.

Any experience, suggestions, comments, thoughts and issues will be helpfull.

Best regards,

Milovan Milosevic

 

[Masbibe]

No any comments ?
Someone needs some more information ?
Like I said before, any comments will be very helpfull.

Milovan Milosevic

 

[sreid]

Here's what I'd do.

Drum 1 [pulls 1 km belt]

Motor 1 = speed master

Motor 2 = torque control equal torque to Motor 1

Drum 2 [Slave Drum?]

Motor 3 and 4 have torque control commanded by Motor 1.

Except there must be an offset torque between Motor 1/2 torque and Motor 3/4 torque such that the tension in the belt between them doesn't ever go "Negative Tension." A 10% offset of the full load torque would be the place to start.

 

[Feg]

Hi

We have done a similar job on chain conveyors but in smaller scale where we used Siemens Micromaster 440's with encoder modules. We set them up in master slave in torque mode and it worked fine. It did take a bit of time to set up properly as you have to make sure the load is shared properly and you need to take care that the over current % is set right otherwise it may be posible to break a belt. I think we did do a quarry job before where we had 3 of 315Kw motors also driving the same belt but it was back a few years and our engineer that done it is no longer with us but it was a similar set up to the above.

 

[Masbibe]

Sreid and Feg, thank you very much for your responses.
Just I have a couple of questions for you:

Sreid: Can you just a little more explain "Negative tension". As I understand "Negative tension" can apear only if first drum (pulls 1 km belt) has clockwise direction of torque (when you look picture that I attach above) and second drum (slave) has counter clockwise direction of torque. Am I right.

Feg: So you wanted to say like sreid said. One master and all 3 others should be its torque followers (one on same drum and 2 others on second drum).

Milovan Milosevic

 

[sreid]

I have never had to design multiple motors on a conveyor belt. But a number of times I've used multiple motors geared to a master gear. In this situation we wanted to keep the drive gears pre-loaded against the master gear. To make this happen at zero speed the Master Drive is pulling slightly one direction and the Slave Drives are pulling the other direction.

For you conveyor there is different dynamics between the Master Drum and the Slave drum and I can envision situations where the slave will slow down faster than the Master momentarily causing the belt between the drums going slack then snaping into tension creating shock loads.