Reliance VS Maxline DC Drive

I have a machine that "draws" (makes smaller) steel wire. This machine was moved about 4 years ago and I am not sure if it actually has operated since.

A few months ago I was asked to check all the drives involved with the system, it has 2 traverse and 2 turntables also. I replaced one turntable 1HP DC motor. I also noticed when jogging that the "drum head" that pulls the wire thru the die acted erratic, I mentioned this to the PE at the time.

Here is the problem: When jogging (no wire attched) the "drum head" (rotating part that pulls and coils the wire) it is erratic but shows no significant loading..ie very small current draw. I said erratic but actually the "drum head" slows down then speeds up at the same location each time. The drum head has a section with rollers and the die attached to one side that probably makes it slightly heavier than at any other point (I think).

When running, with wire attached, the motor load meter reads 150-200 %. I am not sure about the accuracy of the meter but it is exceeding the max current of 342 amps.

This machine was setup with a die to draw wire from .305 down to .271, approximately 11%, it turns out the machine can only do 5% when running.

The PE called in a supposed "drive specialist" to get the system corrected. When they found out it could only draw 5% they stopped working on it, without changing dies to verify that was the problem.

To go back in time a little when they first decided to try to run this machine and we had problems I was asked to check it. I didnt find anything obvious so I started at the beginning...ie did a motor start-up adjustment routine to see if everything matched. With these old system you have to adjust the "minor loop" , which is part of the current loop regulation used for control.

During this process you disconnct the motor starter etc and use a jumper to provide voltage settings provided by the current feedback circuit. You adjust these for +7.5v and -7.5v, you then proceed to set the current limits. I DID NOT get a reading for the +7.5v, all I ever got was zero. I didnt have a card to change it, I went home, the PE found an old card and changed it out but said it didnt change anything. I never found out if that current feedback voltage was working or not.

NOW my question is this: These old DC drives/motors were used because they could be regulated/controlled at speeds as low or lower than 10% easily. From the original settings..ie 1.15 for an adjustable pot from 0 to 10 I assume jog is roughly 11.5% of max which is 1150 prm, roughly 132 rpm.
The QUESTION: Is this a reasonable assumption and should it do this with no erratic behaviour?

Technically this is a rant and I appreciate all those that take the time to read it. I needed to write this out to review it more. I want to say things about a PE but its not the time nor place. I need someone with a size 14 boot to kick me for not getting my BS in Engineering. Today I had to deal with 2 Engineers and if I ever have to deal with that much ignorance again I will go to work bagging groceries...note what I really think can not be said.
END RANT.

I have been working with VS drives for almost 20 years. We all know I aint the sharpest knife in the drawer but give me the manual, tools and meters then I can usually work it out.

If anyone is familiar with these drives and can offer guidance I would highly appreciate it.

Hi, Ron. Sounds like you've got yourself a real museum piece there!

I've done a couple of wire draw machines so maybe I can help.

First, it is likely that the motor is either STAB shunt wound or COMP shunt wound. COMP would be preferred but you don't get your choice. Before doing anything, I would double check to see that the series field is wired to aid (not buck) the shunt field. If this is backward, you can pour amps into this motor and still not get any torque!

Second, the old analog DC drives theoretically could be stable down to stall but setting them up is becoming a lost art. I would strongly recommend upgrading to a modern digital drive like a Reliance FlexPak3000 or ABB DCS400. The ABB has the advantage that it is only a power module (cheap and small!) so you can retain your existing disconnect, fusing, M contactor, etc.

You didn't mention if the motor has speed feedback (tach or encoder) or not. If it does, instability can easily be due to poor speed loop tuning. Yes, you do have to tune the current minor loop properly first. If memory serves me right, the machines I did were running without speed feedback, on armature feedback only.

Wire drawing is a bit of a tough application because the motor has to work just as hard at 1 rpm as it does at full speed. Nice stable speed is essential to get a good consistent wire cross-section. I am confident that a digital drive could do this.

Of course, if the motor simply won't do the required work, then no amount of arm waving or trick tuning will help. Of course, if they don't intend to work the machine at full speed at 11% drawdown, why not put additional speed reduction in the power train and trade speed for torque? Of course, if the machine cannot withstand the resulting forces on the die, etc., then it doesn't take a rocket scientist to figure out that this is the wrong machine for the job. Or, maybe its the wrong job for the machine!

Given the motor nameplate horsepower and base speed, you should be able to calculate maximum continuous torque. Multiplying by the gear reduction, diameters, etc., will give you pulling force. Maybe one of those wiz-bang engineers can tell you if this is enough force to do the drawdown. I would think that that will decide whether to work further on this machine or not. (Don't forget gearbox inefficiencies. Lacking specific data, figure 3% losses per gear reduction stage)

Either way, let me know if I can help further.







Either way, if I can help further, let me know.

Dick, thanks for replying. This subject for them (my employers) has stopped because it was stated by manager that %5 draw was maximum.

I personally checked the minor loop and it did not provide a +7.5v for the feedback...which is thru a USAB card. There is a tach involved but as you know the process involves current feedback. There are alot of cards that regulate alot of things.

I wish I could put a Flex3000 in there or the equvialent.

I have no idea if they will use this machine or not but the decision that it will only "draw" 5% with a 100HP motor when the existing system has a 50HP motor that can do 20% doesnt make sense.

The fact that it isnt stable in jog doesnt make sense...even the idiot drive specialist alluded to this.

I thank you for your assistance...I am so tired of working with and for ....