Simoreg DC Master drive problem

[Dbeauvais]

Please help if anyone can. I must first state that I do not have any sort of vast electronic knowledge. I am a plant manager looking for answers. If your replies are too technical I will be assisted by my maintenance personnel.


I work for a book printer and we have a large fast web press with a 56 kw motor. We had trouble with our Eurotherm drive and had the back up drive installed. That back up was not up to par either so I ordered 2 Siemens Simoreg DC Master Drives (6RA7075-6FV62-0-2). The Eurotherm was out of date and we could only have it rebuilt so I chose to go new. We installed the new drive but had several hours of down time due to parameter settings that were slow coming from Siemens.


Once installed we were off and running. About one month later we started experiencing pre-set speed variation on start up. The press can crawl and run up to 1200 feet per minute. The pre-set speed on start up can be 600 fpm but the press would race to 950 fpm. We called the press manufacturer and they suggested some things to check but we found nothing (power supplies, reference voltage, current). After a couple of months of this speed control problem we started getting motor overheat errors. At times it was so bad the press would slow down and stop when we were running long runs at top speed. The motor is suppose to operate near 40 c and we checked it but it was only 43 c at most. The motor was well maintained, brushes always changed, armature looked good, etc. We even made sure and cleaned off the fan blades and blew out all dust.

The end result was that the manufacturer came in and installed that 2nd Siemens back up drive I purchased. Their claim was that the motor was suspect and could have harmed the drive. They felt there was an issue with the winding's insulation. My question here is that if we have never had a problem with the motor before how do I ascertain if the drive caused the motor to fail or visa versa. A classic, "What came first . . . the chicken or the egg." If I have Siemen fix the drive I will never find out. I feel that since these speed and heat issues did not transpire till the drive was installed that the drive caused the motor's problems therefore adversely affecting the condition of the insulation over a 6 month time span.

Any ideas out there to check in order to prove either way?

[email protected]

 

[leitmotif]

I think you ARE having drive problems and you may (or may not) be having motor problems.

How old is machine? If 10 years and run 8 hour a day at full speed motor is probably OK 24 hours a day I would think about motor shop checking it out. 15 years and 24 hour a day at full speed I would start calling motor shops. 20 years definitely.

Do you have isolation transformers on teh drive? Are they OK.

How much junk did you remove from the motor? How did you remove it and make sure you do not damage insulation (no 100 psi air - NO WATER in air, no poking around in there with steel rods, gentle paint brushes or bottle brushes etc.

Motor temp safety control set at 40 C motor is at 43C and you are getting alarm. GOOD it works little off but worry about that later.
AT full speed full load I would expect it to get warm 104F sounds about right so I would not be alarmed yet over motor warming. I assume you are using probes installed inside the windings.

What is ******t temperature? Michigan in winter maybe not a problem.

Check motor with VOM to ground. After that I would recommend getting a motor shop in to check out motor. They MAY be able to do a thorough check without teardown. DISCONNECT motor from drive before they come lest they meggar drive (besides if you do it - saves on their bill)
OR
DISCONNECT motor from drive and get a meggar and check windings and armature yourself.

The speed issue - my first thought is a worn or dirty pot.

It just may be worth the bucks to get a non factory - independent drives guy who also knows motors to come out and have a look.

Dan Bentler

 

[DickDV]

It is relatively easy and inexpensive to have the motor checked. I would call an EASA motor shop with good DC motor credentials and have them do an on-site check.

That would be the first step in my opinion.

I see that you are in Michigan as I am. If you PM me, I can steer you to some good motor shops.

 

[Dbeauvais]

Dan,

I appreciate the reply. The motor and press is 10 years old and we run hard (24 hours a day, 6 days a week, until recently).

Yes, we have isolation transformers.

Hardly any junk in the motor. We did use air but not 100 psi. We took the squirel cage off to clean it good, not much on that fan either.

VOM to ground good, nothing to ground.

Speed issues, no pot anywhere, controlled by PLC.

I called Dreisilker in Chicago (good reputation) and they repair motors and drives but not Seimens. Appears Seimens does not give up valueble info very easily.

My quest was to test somehow to determine what cause what to go first. If the drive burned my motor insulation I want compensation.

Thanks, Doug

 

[Dbeauvais]

Dick,

Appreciate the reply. We are in Auburn Hills 20 miles North of Detroit. I don't really trust the shops in town. I called Dreisilker in Chicago because of their reputation (I can get a spare motor). They work on drives and motors but not Seimens. They can fix them but they tell me Seimens is hard to work with and won't give out info.

They told me $4,000.00 minimum to, clean, re-coat and bake. Seems a little high.

I have been taken for a ride by motor shops before (charged for re-wind that never happened).

Printing motors are very different I'm told.

Doug

 

[leitmotif]

At 10 years and those operating criteria:
1. It may be time to consider AC drive and VFD. Say 3 to 5K for motor and 8 to 10K for drive.
2. We get old and creaky with age. Same for motor insulation. With DC there is more stuff to get old n creaky.

Re someone responsible for insulation and getting them to pay --
well you will not be the first to try, but
I bet you will be one of the few to succeed.

What really bugs me with your situation is you pay good money for these guys to come out and evaluate drive. They conclude it "may be the motor" -- they may be right and they may be wrong
BUT did not follow up to ensure they are right. Just leave you dangling.

I really hate it when I have to tell people I have no idea what is wrong and I have no idea of what you are going to do and I have no idea of who to call. The good news is that these are few and far between.

Dan Bentler

 

[Dbeauvais]

The guy who suggested Seimen and installed it certainly does not want the drive to be the issue.

 

[DickDV]

It seems to me that you've got lots of "phobias" about brands and motor shops. But, you've got to trust someone, or else go it alone.

Right now you're going it alone. How much production has to be lost before you get some help?

If you're looking to beat someone up over a 10 year-old DC motor that may have failed, I'm not sure I would want to work for you either.

Yes, Driesilker is a good shop but they comes with a huge price. They are not the only reputable motor shop in the Midwest, for sure.

 

[bkottaras]

It seems to me that you've got lots of "phobias" about brands and motor shops. But, you've got to trust someone, or else go it alone.

Right now you're going it alone. How much production has to be lost before you get some help?

If you're looking to beat someone up over a 10 year-old DC motor that may have failed, I'm not sure I would want to work for you either.

Yes, Driesilker is a good shop but they comes with a huge price. They are not the only reputable motor shop in the Midwest, for sure.

I agree with DickDV.
You have to let someone take a look at it and take it from there. It may be cheaper than you think.
Dreisilker is an excellent shop. Done business with them for years.
Since I worked in the printing industry years back I have to say that I ended up doing Drive retrofits quite often, old Fincors, GEs, etc.
The motors were the least of my concerns since they kept going.
Those things can go on forever which leads me to believe that you may have an actual drive issue and not a motor issue.

 

[bkottaras]

Since you have done a couple of upgrades, I assume you do not use an MOP.
If you still do, these things can be notorious and may be the cause of the speed issues at start up and such.
If you do use various power supplies (heat set web presses do) there's a bunch of voltages that can affect the speed as well as the ink, water, etc.
Do you have any issues with other functions of the press besides the actual press speed and the motor?

 

[Dbeauvais]

No phobias DickDV, I was just charged once for a re-wind and found out that it was never rewound. Back then when this happened I had no maintenance staff and I was a one man show. When you don't really know the business it is easy to get fooled. Research is key.

If you ask am I upset if a drive cooked a good motor, yes I would be. I believe in printing great books and offering my customers the best money can buy, I expect the same from my vendors.

Any suggestions on a motor shop closer than Chicago. Why do the symptoms go away when the cabinet (where the drive sits) is left open.

 

[bkottaras]

No phobias DickDV, I was just charged once for a re-wind and found out that it was never rewound. Back then when this happened I had no maintenance staff and I was a one man show. When you don't really know the business it is easy to get fooled. Research is key.

If you ask am I upset if a drive cooked a good motor, yes I would be. I believe in printing great books and offering my customers the best money can buy, I expect the same from my vendors.

Any suggestions on a motor shop closer than Chicago. Why do the symptoms go away when the cabinet (where the drive sits) is left open.

Because it is a DRIVE issue and not a motor issue.
You just answered your own question.
Most people would run the press while waiting for a new drive with the doors open.
Dead giveaway that their drives were about to be toasted.

 

[bkottaras]

One more thing, the drive has its own cooling fans, external I assume.
Do they work? or any one failed and since then you started having all the issues you do?
separate fusing and/or power supplies are used for fans on some drives.

 

[leitmotif]

Because it is a DRIVE issue and not a motor issue.
You just answered your own question.
Most people would run the press while waiting for a new drive with the doors open.
Dead giveaway that their drives were about to be toasted.

I love it -- six posts later we get down to the nitty gritty. Once again LACK OF COOLING.
I wish I were paid for every time I see this.
If you want good perfomrance from any machinery
DO NOT OVERHEAT.
Goes double for electrical and probably triple for solid state including drives.

Recommendatins
1. Buy new fans and BIGGER ones
2. Paper is a good insulator both heat and electrical. If you want to keep your equipment cool keep the paper dust off.
3. Do not use those aluminum filters or the scotch brite filters on your cabinets. Throw em out.
4. Get a filter outfit to recommend filters with a 80% particle size cutoff rate.
5. Set it up so the fan suction is filtered and fan discharges to cabinet to keep cabinet positive pressure (no dust gets in thru the "seals".
6. Put a thermometer in cabinet and try to keep temp below 90 -- 80 F would be even better.

Dan Bentler

 

[bkottaras]

I love it -- six posts later we get down to the nitty gritty. Once again LACK OF COOLING.
I wish I were paid for every time I see this.
If you want good perfomrance from any machinery
DO NOT OVERHEAT.
Goes double for electrical and probably triple for solid state including drives.

Recommendatins
1. Buy new fans and BIGGER ones
2. Paper is a good insulator both heat and electrical. If you want to keep your equipment cool keep the paper dust off.
3. Do not use those aluminum filters or the scotch brite filters on your cabinets. Throw em out.
4. Get a filter outfit to recommend filters with a 80% particle size cutoff rate.
5. Set it up so the fan suction is filtered and fan discharges to cabinet to keep cabinet positive pressure (no dust gets in thru the "seals".
6. Put a thermometer in cabinet and try to keep temp below 90 -- 80 F would be even better.

Dan Bentler

Thanks Dan.
Well said!
I've also seen large DC motors used in printing where they had manufactured "blowers" sheet metal and all and a motor blowing air on the actual DC motor to cool it down.
Nothing to do with the cabinet or the issues of the OP but thought I'd throw it out there.