Shopping for a conveyor system

[RoTaTech]

Thanks drawson, that was why I asked if anyone had experience using one drive with multiple motors.

But I still need to individually start/stop the motors, so that as one line fills up, I can stop the upstream conveyor.

I know it's not recommended to disconnect the motor from the drive (at least in a one-to-one application, but if, for example, I always left (at least) one motor connected, then when I want to shut down that last conveyor, I just stop the drive .

I'll ask AB, et.al., about it, this week.

 

[drawson]

If you need to individually start/stop each section you might be stuck with a drive for each.

I've never seen it done but you might be able to use a single drive to rectify and supply 17 motor starters the same way you would if running them across the line. That would enable you to set the speed of the entire line and still start/stop each section with discrete I/O. I don't know what dynamic effects switching those loads would have on the drive. You should probably talk to a supplier about that. You would definately want to make sure you install line reactors because it could create some strange harmonics.

 

[Ken Moore]

The one thing you have to remember, in the US anyway, is that if the motor is more then 50' (or out of sight) from the disconnect panel then it must have its own disconnect; so factor that into consideration.

That is a safety situation I have not considered or dealt with that I can remember. I know with a VFD you should not use a disconnect after it, can be detrimental to the drive. In this case if you stop one motor though you need to stop them all.

I don't remember the exact article number, but there is an exception in the NEC that allows local disconnects to not be installed. I also don't remember the exact verbage, but it says something to the effect, that local disconnects may be omitted if, the MCC bucket is lockable, you have a formal lockout/tagout program, and the MCC is in a restricted access area.

 

[paulB]

About fifteen years ago when I was working in the newspaper printing facility we have had multiple conveyor sections with individual motors of 1/2 to 1 hp, which were driven by one Toshiba drive/invertor. Each motor was connected to the inverter by contactor. Contactors were controlled by PLC. These conveyors were delivering newspaper from printing press to the stacking machines. You were able to select different conveyor routes by selecting conveyor switches and turning appropriate contactors ON or OFF. Motors were connected by "piggy tail" 3' cables with the plug. When jam needed to be cleared motor was unplug from receptacle.

PaulB

 

[CheezSarge]

Hi Guys,


The NEC article in question is 430.102. It does say that a disconnect shall be in the line of sight but no distance is given. The first exception under B is if the breaker that supplies the motor is capable of being locked the line of site rule is then not required. Pretty much what has been stated earlier

Darrell

 

[RoTaTech]

Thanks, Paul B. At least I know it is do-able.
Rob

 

[Derek McFarland]

ArmourStart contactors with VFD feeding line could be a possibility. $ might be high.

 

[JHarris]

Darrell,

Thanks, I found the same in 430-102(b) this morning. As a said before, it's nice to have them, but sometimes the cost and problem of finding an acceptable mounting location will make you think twice if they are not needed on a daily basis.

 

[rsdoran]

Maybe it has just been my experience but plants with long runs and possibly multiple conveyor systems usually have a daily maintenance concerns pertaining to them.

I have never used a VFD with multiple motors and not sure I ever would for a production line if I could avoid it. I can visualize too many scenarios that would create issues for maintenance.

The rules have changed slightly because it does not state a distance but it does state in Article 430.102 that the disconnect means must be before the controller and in sight but there are exceptions but you must meet the requirements of those exceptions.

That would mean only one disconnect could be used for a VFD running multiple motors so if lockout was needed all motors would have to be disconnected.

430.109 mentions using cords and plugs as disconnects but you will have to determine if your situation applies.

I would suggest you obtain the NEC Handbook, it is my understanding it and CEC are harmonized now. The handbook offers more detailed information and pictures to "translate" the codes.

You can view the NEC codes here: http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp

Every situation is different, just have to determine your needs then do what is necessary.

 

[Joe_WaZoo]

Someone suggested the use of DeviceNet. Here are some photos of an application I worked on some time ago.

Conveyor

Here is another project where the ArmorStart VFD's were used in conjuction with DeviceNet I/O stations.

Bread Line

Joe_WaZoo

 

[nif]

Hi!

I would personally use one VFD/motor, because if all of the conveyers aren´t exactly the same size they will be moving in different speeds.
Do you know if they are going to use pressure washing in the factory?
Then all of the equipment should be atleast IP65-67 protected.

The best way would be to have the vfd next to the motor in the field, then you wount get any voltage drop in the wires.
You will only need to bring the feed down to the motor where you can install the safety switch for the maintenace.

you can use motor-vfd packages or Ip 65 rated vfd:s next to the station.
i have made a reject bottle line in a brewery in Finland and it´s much easier to adjust the speeds/monitor the motors if they are different.
Also if you only have one vfd and it blows up....the whole factory stops.

Almost every manufacturer of VFD have fieldbuses where you can use one VFD as master and the other ones follows the signal from the master

 

[Lancie1]

Rototech,

Yes, I have used one drive for multiple motors.

Yes, there are drives that have options for contactors. VFD drives have electronic overload so do not need an additional separate overload.

For this case only, my recommendation would be to use a small VFD AC drive at each motor, mounted underneath the conveyor. Use a receptacle and plug as a field disconnect, because it is only 1/2 HP, 1 Amp at 480 volts. Put a main disconnect for all the motors somewhere. Keep 1 spare VFD, so when one fails, you unplug it and slap in the spare. Meanwhile, the other conveyors can still run, if that is any benefit.

It is no problem to run a 4-20 miliamp current loop for 350 feet. Use a master speed conrol that sends the same signal to all drives. You would have to make some individual tuning adjustments at each VFD drive to get the exact same speed, but Your required +/- 5% should be no problem without any individual adjustments whatsoever.

You will not need additional motor starters. If the motors need to be controlled individually, add at least two #14 signal wires to each VFD. Nearly all VFD drives have at least 2 or 3 input terminals that can be used for Start/Stop and other functions. I would go ahead and run a 5-conductor #14 cable to each drive. Then you can have Start/Stop, Drive Enabled, and Drive Tripped indicators back to your PLC or control room, even if you don't use them initially.

Let the VFD serve as the motor starter and the overload. If you use starters, you will have additional unnecessary parts, and will still need individual control wires to each starter. Forget the starters, you don't need them here.

 

[nif]

If you use a fieldbus system you would only need one wire with two conductors, not 119 conductors + the same amount of I/O..?

 

[Thomas]

Devicenet stinks!

If you use a fieldbus system you would only need one wire with two conductors, not 119 conductors + the same amount of I/O..?

​

With a fieldbus (like DeviceNet) it only takes one fault to take out your whole system. One little bit of forktruck impingement and the day is ruined.

These things look great on an installation budget. They stink for maintainability.

$0.02

 

[rsdoran]

If you use a fieldbus system you would only need one wire with two conductors, not 119 conductors + the same amount of I/O..?



​

With a fieldbus (like DeviceNet) it only takes one fault to take out your whole system. One little bit of forktruck impingement and the day is ruined.


These things look great on an installation budget. They stink for maintainability.

$0.02

In the case of a forktruck (or any similar type destructive force) you would probably damage any control feed and/or the supply lines so what difference would it make? With DNET, and I suspect any fieldbus system, you can remove/disable any device if needed.

Most of the plants I have dealt with recently are putting guardrails beside conveyors or machines when forklifts travel is near or parallel to it, especially at forklift pickup point?

Every situation is different and I do not know all the details in this situation but from what he has stated I think a VFD for each motor would be the best option.