one VFD driving 3 motors? Has anyone any experience with similar setups?

[Fred Floggle]

wow , we are getting technical now!! " the warmest one is the one taking most load" .

I am at present commissioning a drive system where there are 45 motors driven from one drive , ( and no , they don't run at slightly different speeds ) drive is a GV3000, and we don't do anything particulary clever with it . my cable length is probably closer to 150' , and we keep the skip frequency low .

In your application , what do you have to compensate for different diameters and coeefficients of friction ? It will be very difficult for you to balance the loading with only one drive . Would seem like a good application for a torque following set up - just a thought!

 

[Sliver]

whew.. all done. (well almost)

Thanks Dick and Fred,

"what do you have to compensate for different diameters and coeefficients of friction ?" Nothing except new drive wheels that are all the same diameter for now. You should see the wear on the idler wheels that they put back on the trucks. Yikes!


I left the over current and overload settings at default.
I think overcurrent is 27 amps on this 25 hp drive.

After some production people timing one pass and adjusting the prest frequency we came up with a final value of 37Hz to be roughly equal to our previous setup's speed.
I ran into some problems getting it to reverse with 2 wire control and found myself locked out of TB3 term22 (par242) default value is Rev/For and I couldn't change to reverse only. I was about to come in and log on and send a SOS to PLCS.NET when I finally tried to play with password. It allowed me to modify the password and then I had access to all parameters. Strange that I could change everything else without going through any password.
So anyway the stacker is running and all the suits have gone home and I have some documentation to do.

One question though.

I have a chopper module and resistor bank but I have never seen the light come on to indicate the chopper is being used. I have changed the Stop Select 1 parameter from "coast" to "ramp" to "ramp and hold" to "dc brake"
I am assuming with DC brake there are other parameters I must set.
Any suggestion? The stacker seems to be working ok anyway, so I have room to play. (Unless I get reassigned before I can put a big red bow on it)

Thanks for all the help and encouragement,
The Brass is all smiles on this one,

Brian.

 

[Johnny Rotten]

What kind of starter/overload are you using? Make/model/size?

A/B has had major problems with their European style starters/overloads. They are discontinuing some of them.

I worked on a conveyor system where we changed the motor and starter such that it would go 'forward' and 'reverse'. We used A/B European style starters. They DO NOT work well. The electronic overload section trips way too fast. Did not have to trouble-shoot until winter, of course, as it worked fine up to that point. Changed to Seimens 'bi-metalic', no issues.

If your equipment is in a harsh environment, A/B European style overloads are useless.

Maybe thats too simple.

Billy Bob

 

[Fred Floggle]

Would agree with your comments re o'loads - The job i'm commissioning now is for Rockwell , and we have specified Siemens o'loads , they are much more "tolerant" of unpleasant site conditions - providing a sensible spacing is maintained between devices.

In reply to the question regarding braking , please remember that DC injection braking is different to regen braking (your application)

 

[DickDV]

Well, let's see here, Sliver. Several issues. First, congrats on a successful startup! Other than making a living, that's the biggest reward in this line of work for me---seeing the suits smile and then go away!

Second, some drives have "layered" protection. Some parameters can be adjusted with no password, some with the first password, some with a second level password, and so on. Reliance, as I recall, used to do this.

Second, I'm not exactly clear which stopping mode you ended up using but I'm assuming "stop and hold". This would be a ramp down to stop and then DC injection to hold the load stationary. You will normally have a timeout parameter somewhere for the DC injection to stop---you can't keep doing that to a motor or it will overheat. The time delay would normally be used to engage a mechanical brake for longer term holding purposes. Sometimes there will be a braking intensity parameter as well. This should be set at the lowest level that reliably keeps the machine stationary. The parameter adjusts the amount of DC current going thru the motor stator windings and thus the braking torque.

Since you have a decel ramp to stop and also when you go from a higher to a lower speed, there is a chance that you will need some regen or snubber braking. It sounds like your decel ramp is long enough to avoid braking, at least in cold weather. When it gets warm and the machine has less drag, you might see the braking system start to work. It's good insurance even if it isn't often used.

As far as different wear rates on the wheels, don't worry about it. Each motor is free to slip somewhere around 2% of basespeed which usually works fine distributing the load and compensating for minor differences in the machinery. You can expect that the motor on the largest wheel will take the most load. Check it occasionally for heating.

 

[Sliver]

Back to the well

This project was undertaken and completed in a short time frame thanks to this site and everyone who helped out. Special thankyou to DickDV. The stacker has chugged away very reliably since.
9 years later and they have asked me to do a few upgrades and I was able to reread this thread to refresh my mind on the issues. One such issue is that we may have to replace the original bimetallic overloads and the other style we use around here, and have in stock, is electronic/solid state. At first I thought I could swap them out but thought I remembered somebody warning me about that and if you read the whole thread the issue about using thermal overloads was raised. I assume that means that electronic overloads are not recommended for this application.
I have a call in to our A-B Drive rep but in the meantime if someone can verify this, I will proceed to source a new bimetallic equivalent overload relay.

Thanks,

Brian.

 

[DickDV]

Unless the electronic overload specs specifically mention being suitable for PWM power, I'd stay with bimetallic overloads.

 

[johnd_125]

This may be a side note but I've had some success with the Great Minds by just using a clamp on ammeter. When dealing with a motor tripping issue, they typically want to blame some programming on the VFD. Or maybe they think a VFD is a reasonable solution.

If you can show them the motor running amperage is over the NP rating, and explain to them the motor is overloaded, then even their big brains can often process that and solutions tend to veer more towards the sensible....