Motor control center using devicenet

We have 15 5 hp blower motors running air tables. Today I noticed production people still starting as many blowers at once as their hands got fingers. I have told them many time the inrush this is causing but they just don;t understand. I was wondering if anyone has used allen bradley powerflew series drives on devicenet controlled by a micrologix 1200 fprocessor.
I want the production people to have one start button. The processor will time everything out and stage them so that no 2 drive are starting at the same time. The setup now is starters which is hard on all the belts.pulley,motor and the blower itself. I would like to use drives and set the acceraction time to say 5-20 sec to gradually get the blower up to speed.

What all will i need to make this project come together. I am completely new to devicenet but i like the concept of hooking up the line and motor phases,device net cable and an external etop.

with device net can i transmit my desired speed. The management would like to see the blower motors slowed down during break time to conserve energy. they have a 15% goal on the electric bill.

thanks ahead of time.
I find this site to be extremely useful and visit everyday. To someone learning this site is unreplacable

First, using inverters on the motors will get you reasonably fast acceleration times without any inrush current at all so you could conceivably put one large drive on all of the motors and start them together---still no inrush!.

If you want to drive each motor separately, that's ok too and, with many drives today, you can daisy-chain the drives to start sequentially so you could use a single start button to get all of the fans to run up to speed one-at-a-time.

I don't see any need to use external processors or devicenet on the system you described.

Hey ya,

I have configured a few types of PowerFlex drives to run over DeviceNet. You will find that programming the drives to run at a set speed with a certain ramp-up time using RSLogix 500 is pretty easy; the hard part is getting your network configured properly with RSNetworx. Not hard, but tricky.

However, if you have no variable speed requirements for the blowers apart from lunchtime, consider using adjustable soft starters. These require no logic or PLCs and can be substituted with minimal disruption. Then make your operators turn them off at lunchtime.

Likewise, you could use a simple series of adjustable on-timers to sequence startup from the single button. Again, no extensive PLC retrofit required, only a minimal amount of wiring.

However, your system will be much more extensible with a PLC providing the brains

Some useful general info here

Binaural said:

Hey ya,

I have configured a few types of PowerFlex drives to run over DeviceNet. You will find that programming the drives to run at a set speed with a certain ramp-up time using RSLogix 500 is pretty easy; the hard part is getting your network configured properly with RSNetworx. Not hard, but tricky.

However, if you have no variable speed requirements for the blowers apart from lunchtime, consider using adjustable soft starters. These require no logic or PLCs and can be substituted with minimal disruption. Then make your operators turn them off at lunchtime.

Likewise, you could use a simple series of adjustable on-timers to sequence startup from the single button. Again, no extensive PLC retrofit required, only a minimal amount of wiring.

However, your system will be much more extensible with a PLC providing the brains

Click to expand...

I'll second the recomedation to use the soft starters. The SMC-3 soft starters have a built in bypass contacts and are price competitive with Nema starters (actually a little less than a Nema starter.) I have also used the SMC-FLex soft starters on device net, but for this applicaiton, the SMC-3 is probably more than adequate.

With 15 motors to start, adding all those timers is a lot more money than a ML1200, which is around 300 bucks. Go with the PLC.
Look here
http://www.mrplc.com/kb/index.php?page=index_v2&id=14&c=12
for an example program and tutorial on staging motor starting on a 10 motor set up.

Do I miss something, but ML1200 does not have DeviceNet scanner.
So I assume that ML1500 should do the job

Regards
Lauri

You are right, the ML1200 does not have a device net scanner. If the OP chooses to use soft starters or drives, he will have to wire them directly to IO points if he remains with the ML1200.

Personally, I would use the ML1200 and SMC-3 soft starters. With 15 motors any capacity between 0 and 100% can be selected in 7% steps. There probably is not a need for drives.

Off hand does anyone know the price for a smc-3 soft start for a 5 hp motor. I think this will be adequate for the project. This will allow the blower motors to come up to speed slower to limit belt sqealing and wear&tear. It will also do away with the inrush problems

For future reference. Does powerflex devicenet drive allow you to set the speeds(hz) from a plc. I know you can start,stop and etc but was unsure where the speed input came from.

AB has online shopping that will give you standard retail pricing: http://shop.rockwellautomation.com/RA/index.jsp?scrnCurrentStore=RA

DeviceNet information in detail can be found at www.odva.org DeviceNet can offer alot of features but does require some learning time, there are variables involved.

This is an example (not all inclusive) of what can be communicated using DeviceNet...note you can have numerous devices and each device can offer an I/O table.

Those of you that are recommending softstarters are possibly overlooking one important point. Softstarters reduce inrush currents but do not eliminate them. In fact, with a motor that requires 6-8 times nameplate current to start DOL, about the best a softstarter can do is cut that to 3 times nameplate. If three times nameplate is acceptable, then that is the lowest cost solution.

On the other hand, if you want lower or NO inrush, then you have to start the motors synchronously and to do that you need an inverter. Further, the original poster indicated that during breaks the motors were to be "slowed down". That tells me that stopping isn't the plan with break time. If it is, that would be a further plus for softstarters rather than inverters.

I guess that this string gives the original poster some good info on how to make his/her choices. That has to be a good thing!

Now that I think about it, just sequencing the start may be just as easy and effective as converting to drives etc. An ML1000/1200 could be used with the existing hardware to just sequentially start the motors in order. This would allow them to just shutdown the motors on breaks and restart on return. Technically though 15 5HP motors is the equivalent to one 75HP motor which is common to start DOL. The cost of soft-starts or drives could take years to recuperate in electrical savings...this would require an in-depth study.

Depending on discount an SMC-3 is $300, which is about the same or less than an AB NEMA starter, so the cost would be around $4500 plus accessories, time and labor.

I guess it all depends on what the future plans may be.

The 15 motor are divided up into 3 different tables. One has 8,one and 4 and the last has 3. Depending on product not all of them need to run. They would like to be able to slow down the drive while on break and when not currently in use. I figured slowing them down would be better then a complete shut-off becuase you wouldn;t have to wait for the timer to cycle through And the inrush to start from a dead stop. I was reading on the ab site that the devicenet interface for a powerflex will control 4 drive.
<LI>PowerFlex 40 DeviceNet Adapter
22-COMM-D
<LI>Multi-Drive mode allows up to 4 additional PowerFlex 4 or 40 drives to be connected to the PowerFlex 40 on DeviceNet (total of 5 PowerFlex 4/40 drives on one DeviceNet node)
how does this work. Special cables etc.

DickDV,
"First, using inverters on the motors will get you reasonably fast acceleration times without any inrush current at all so you could conceivably put one large drive on all of the motors and start them together---still no inrush!."
Are u shure you're not a plumber?

2004sk4 said:

The 15 motor are divided up into 3 different tables. One has 8,one and 4 and the last has 3. Depending on product not all of them need to run. They would like to be able to slow down the drive while on break and when not currently in use. I figured slowing them down would be better then a complete shut-off becuase you wouldn;t have to wait for the timer to cycle through And the inrush to start from a dead stop. I was reading on the ab site that the devicenet interface for a powerflex will control 4 drive.

Click to expand...

Technically start up time from stop or slow to run will not be that different, we are talking a difference of seconds at most. The one important factor to note is that if not running they dont use power, if running they do.

If each table runs the motor speeds at the same rpm then you could do as Dick mentioned and use ONE DRIVE for each table. I personally do not see a need for DNET nor the PLC for the application as stated if a drive is used, the drive offers ramp time and numerous control features plus they usually have a display that can show conditions, alarms etc.

From the way the original question was stated I am assuming the system is DOL and just uses a stop/start control with little if any other components that operate in conjunction.

It is good when an opportunity arises to use and learn newer technology BUT the application should NEED it to justify the cost. The investment in a changeover incorporating 15 drives and possibly 15 inverter rated motors, a plc, RSNetworx software and adapters, power supplies, cabling, possibly new cabinet, and time may not be justified for this application. Just a wild quess off top of my head and the cost will easily exceed $20000.

As I mentioned before, one PLC may offer more control than you have now but drives could possibly offer the best efficiency...again it all depends.

Thanks for the plumber comment. That's much appreciated. I understand the drive will have fast acceleration without any inrush. i wanted slower acc to eleminate the DOL belt squealing.

I am not to familiar with the concept of using one drive for multiple motors.
Let's say i have 8 - 480volt 5 hp motors on one table.

would i inturn need a 40hp drive.

how does this setup work if i have to lock-out one or two for maint.

Would each drive have it';s own overload right after the drive.I have disconnects mounted at each motor to maintain the line of sight to the motor.

Thanks

When sizing a drive for multiple motors, you will need to take the Full Load Amps, add them all up and then add 10% of that number for each motor more than the first one. So, let's say your motors are identical and each has an FLA of 8.0 amps. 8.0 X 8motors is 64 amps. Add 70% to that so 64 times 1.7 is 109 amps. Pick a drive with continuous running amps of at least 109 amps. There is little or no overload required so a variable torque or normal duty drive would be right. The extra 70% ampacity is needed to avoid Fault problems on starting due to the extra-ordinarily low impedance of all those stationary motors in parallel.

Also, you will need fuses and an overload block for each motor. A fused disconnect is useful if motors will be pulled offline occasionally for servicing. If you have three or less motors in parallel, you won't need the fuses even tho they are still a good idea.

The drive will need to be run in scalar or V/Hz mode. Sensorless vector will not work. The normally closed contact on each remote overload block must be wired into a series closed loop and applied to the drive Run Enable or External Fault terminals causing the drive to stop when any one of the overload blocks calculates excessive motor heating.

This arrangement is a very useful way of getting multiple motors to operate at the same speed +/-2% without lots of small controllers. You can set the accel time for whatever ramp time will get you FLA on each motor and you will have a nice no-belts-squealing, no inrush start every time. A longer accel time will likely produce a start with lower currents than full speed operation with full speed load only being reached at full speed.

I've done many of these systems, the largest being a steel slab roller table on a roll mill with 47 1.5hp motors, one on each roller. The drive was rated 125hp due to the oversizing mentioned above. This one also used full regen braking due to the need to reverse the steel slab at the end of each pass thru the roll mill.

Those kinds of jobs make this work fun, at least for me (the plumber!).