Simoreg DC Master drive problem

[Dbeauvais]

No, we are near Detroit and the press is a 46" cut off Timson printing a 52-1/2" roll.

 

[leitmotif]

I've done a few pre and post.
Pre PLC would be Analog drives such as the AB 1336 or whatever the part number was.
Makes no difference to me.
I've used eurotherms, Control Techniques, whatever the customer wanted and was within its budget.
The drive gets an analog signal to ramp up to a point and maintain speed.
Either PLC or a speed pot will do the job.
Since the tach goes to the PLC and fed to the drive I see no issue with signals unless you have had the uncontrolable ramp up before the install.
I used to retro Harris M110, 110Bs, 300s etc.
I've used all kinds of drives and usually ended up using the existing ones as we were doing primarily the controls/PLC upgrades and the things ran forever.
I cannot see how a "bad" motor worked without a hickup with the old drive, then the Eurotherm and now it is acting up.
I'm out of options here.
No alarms, cooling is more than enough (according to you),no changes were made recently besides the new drives(right??), the only things left are analog signals somehow get scrambled and screw up the drive or the drive itself is bad or misconfigured.
Bringing someone in with a megger wouldn't hurt at this point.
A couple of drive experts on here , you may get something that I've missed so far from them if they decide to jump in DickDV & Leifmotif (sorry about any wrong spelling, not intentional).

I think it is time to step back and think about things.
1. This is a 10 year old machine
2. Motor winding temp sensors are set for 40C. They operate because he is getting 43C in the motor.
3. VFD cabinet is now overheating. I am thoroughly confused why maintenance took a heat gun to the VFD cabinet.
4. YOu mentioned 24 / 7 operation and said you run it heavy.
There was no mention of PMs or periodic checks.



OK so he has a motor that is getting warm. He has a VFD that is getting warm. That indicates to me they are fully loaded.

BASICS
Motor will produce the torque demanded by load.
Motor will demand current proportinal to load from VFD
VFD will supply that current within its setup configuranion parameters.

Now then since the machine is 10 years old maybe the problem really comes down to that it is getting old and worn and the total torque demanded is at the upper bound of the motor (thus heating). I would recommend going thru the machine and looking for wear and bad bearings, gearboxes etc. For sure I would check gearbox lubricant levels and lube quality. One of those IR heat detectors may be quite useful in finding bad bearngs and hot spots in drive train.

My bet is your maintenance is only to keep this running. I know how it goes "we'll check that after this order" then the next order gets dumped on and they want it yesterday.

I would install ammeters on AC line supplying drive all three phases. I would consider installing ammeters on both shunt and series field / armature and keep an eye on these currents and voltages while machine is running. This will for sure tell you how heavy you are loading motor. It will also tell you if you need to have shop check out motor.

The "high" speed at startup still bugs me. I wonder if your tach gen is not slipping. I would pull at a MUCH later date and do a bench check of it to ensure RPM is proportional to voltage and double check the drive. Not a problem for now and can wait until later.

Dan Bentler

 

[Dbeauvais]

You gave me exactly what I wanted. I appreciate your advise. I'm going to check everything. The tach was the 1st thing we checked and whether running over or under it registered. The tach does not feed back into the motor control, it feeds to PLC then PLC sends signal to controller. The man who installed the drive said our field was degrading but we never had any power issues with the old Eurotherm drive in. He also said the moter never really over heated (even though it forced the press down to a crawl). He said that the Thermister never activated and he could tell by the drive's fault log. A pressman told me the motor was so hot he could not touch it.

The back up drive is in the press now (I bought 2) and we have a fan in the cabinet and everything appears to be working (no overspeed or heat). If this is a field problem we could damage the back up drive I guess.

Two more things developed since my original posting.
1.) The original electrician that installed the drive was somewhat of a rookie and he was here for 3 days on a 1 day job. It was not his first drive install though and he seemed knowledgable. He was having issues with downloading the parameters. The lead electrician came in and finished the job.
2.) We had our motor in the shop on 4-8-08 for cleaning, bearing change and to turn down the comutator a little. The report shows the field was good 1 year ago.

The reason we checked the cabinet temp was because we had noticed that both symptoms went away when the cabinet doors were left open. We wanted to know what kind of temp was in that cabinet during a problem.

 

[Dbeauvais]

Oh ya, we had already checked the temp of all the gear boxes. All 4 were normal. Did not check bearings though.

 

[leitmotif]

Oh ya, we had already checked the temp of all the gear boxes. All 4 were normal. Did not check
bearings though.

If gearboxes are not overheating they should be OK at least for now. IF it is easy to pull a cover I would do so in a dead time and visual check for wear and if you need to lash ie slop beteen gears and shafting.

I would definitely add some instruments on this. Keeping an eye on amps an volts on motor will go a long ways to avoid catastrophe. This is old equipment - with good monitoring and a little care you may easily get another 10 years out of it.

Dan Bentler

 

[DickDV]

This whole thread is just about making me dizzy due to the amount of dis-information and wild speculation going on. Saying things like "this is a 40degC motor and it was measured at 43degC" is just plain ridiculous and reveals a total lack of knowledge about motor nameplate data.

Saying things like "a pressman told me that the motor was too hot to touch" is also ridiculous since the poorest grade insulation rating on motors is hot enough to blister your hand.

Saying things like "the motor's field is weak but it runs ok on the old drive" doesn't make any sense. A motor with a weak field behaves entirely differently than described. Further, opening the cabinet doors would most definitely not make the problem go away.

Saying things like "the motor made the drive go bad" reveals a complete lack of understanding of how drives protect themselves. A modern drive is so good at that that you can short the output and the drive will simply fault out.

Saying things like "the drive heatsink measured 129 degrees" doesn't seem logical either. How is any heatsink supposed to transfer heat to the surrounding air if it doesn't run warmer than the surrounding air?

Sorry, but my purpose is not to irritate anyone with this but simply to jar someone's eyes open a bit. YOU NEED A QUALIFIED TECH ON-SITE TO TROUBLESHOOT THE PROBLEM AND DEFINE WHAT THE REPAIRS WILL BE. And, yes, you will have to pay that person some serious money to do this for you. We can be a lot of help but not when most of the data coming our way is nonsense.

As I said before, how much production has to be lost before the right thing is done here? Either way, it is going to cost you something!

 

[jawolthuis]

Leitmotif, I think when he said "heatgun" he was referring to an IR heat gun that measures temperature by measuring the amount of infrared energy being emitted by an object.

 

[leitmotif]

Leitmotif, I think when he said "heatgun" he was referring to an IR heat gun that measures temperature by measuring the amount of infrared energy being emitted by an object.

Awww for petes sake - I thought he was referring to what is commonly called a hair dryer. Never dawned on me it was a Temperature Detector. No wonder I was mystified at why he was heating a hot cabinet.

Dan Bentler

 

[DickDV]

Gentlemen, in an attempt to put a positive spin on some of what I've said earlier, when a motor nameplate says 40degreesC, it means that, in a 40degreeC environment and at full load plus service factor, the motor will not exceed the temperature of its rated Insulation Class.

For example, the lowest grade industrial insulation class is B. Class B has an 80degreeC rated rise which means that the 40degreeC am****t temperature plus the 80degreeC rise is the maximum temp for the insulation. That's 120degreeC! Water boils at 100degreeC! You will blister your hand at 65degreeC! And that's the lowest rating. Odds are the motor is Insulation Class F which is good for 25degreesC more for a total of 145degreesC.

Can you see why reading a motor temp of 43degreeC is no useful information. Likewise for, "it didn't burn me hand so it's ok".

Hope this helps stir some better stategies here.

 

[cjd1965]

Hi
Interesting thread, curious as to who decided original drive was kaput and recommended Siemens. I would called in Eurotherm/SSD/Parker to check over the old drive and then, if required, got them to retrofit a modern equivalent.

Using 'electricians' to fit and configure the drive doesnt seem ideal to me, no disrespect to anyone intended. This is a job for a specialist drive engineer, especially if your changing brands.

They would then have to 'carry the can' regarding these issues.

Sometimes you try and save a penny but end up spending a pound.....

Good luck

 

[Dbeauvais]

Sorry for the ignorance DickDV, but that's exactly what is is. I'm not an electrician I am a manufacturing manager. I'm forwarding infromation that I am being told. I'm trying to find an electician to come in and test everything and a spare motor so I can send this motor to a shop.

My maintenance man knows electronics rather well but he is limited somewhat. He swears by the fact that all symptoms stop when he was called in on nights and just had the cabinet doors open.

 

[rdrast]

Hrm.
Get the motor looked at, and even the interconnect wires especially to the field shunt field.


Work with me here.
A DC motor depends on the field flux to develop torque, if the field is dropping out, you need to push more armature current to maintain torque. Now, if the drive is set up PROPERLY, it should be running the field in current mode, and not voltage mode. Field current = Flux. Field Voltage control is not nearly as precise, and changes the motor flux as the windings change temperature.

What kind of feedback are you using on the drive? Tachometer? Encoder? None? Motor mounted? Remote mounted?

How is the armature circuit actually wired? Does the motor have series fields? If so, they should generally NOT be wired in when running off of a current-generation drive.

So, things to check:
1) Series Fields in motor disconnected.
2) Shunt field coils okay (and wired properly, normally in series, and in PROPER series. Mag-check them to be sure. I've had motors with mis-labled shunt field leads, which can cause the field to be completely cut off magnetically, but functional electrically.
3) Drive is configured properly for base (and if needed, extended range) field current control mode, NOT voltage control.
4) Motor has a feedback device, and the drive is configured to USE it, and is not in Armature feedback mode.
4A) Feedback device is properly coupled to the motor, with a proper coupling, and has no slip or misalignment. FALSE BELIEF: Couplings allow for misalignment. That is right out, they don't.
5) Was the drive properly self-tuned? On the Siemens Master DC Drives, this involves Current loop tuning, CEMF (Field) tuning, and Speed Loop tuning. Make sure all three have been properly completed.
5A) The Siemens Master drives are generally OVERLY aggressive when going through the speed loop self tuning, so you will probably have to go back and manually drop the loop gains quite a bit. Typically, you don't need much more then 2.5 to 5 for proportional gain, and the integral time constant should be (typically) in the range of 0.3 seconds to 0.6 seconds.
6) Has the motor actually been megged? A simple VOM really won't do the job. Meg it.
7) Any shorted armature bars? Quick test: disconnect the load, energize the field, and spin the rotor slowly by hand. If there is a bind with the field energized, and it goes away with the field off, you have shorted bars on the commutator or shorted windings in the armature.

 

[Dbeauvais]

This was no ordinary electrician. He's the head electrician from the company we bought the press from. He had several of these Siemens drives installed on older presses.

 

[DickDV]

DBeauvais, if you will PM me, I will give you some trustworthy contacts in your area. I have been in the drive/motor business in LP of Michigan for 20 years and pretty much know who can and who can't.

The trick is to find someone with good credentials in DC. DC is rapidly disappearing except for a few narrow kinds of applications and DC techs are dying off and retiring.

I would put the contacts on the public forum here but we are not permitted to promote or sell specific brands or invite spammers.

 

[Dbeauvais]

cdj,

I had 2 10-year old Eurotherm drives that came with the press. Both had been rebuilt at least once. The press had an unusual problem unrelated to the motor that the manufacturer could not figure out. Their final guess was to swap out the drive to the back up drive to see if it resolved the original problem. It did not but 5 hours later we blew a capacitor on that back up drive (our fault for not throwu=ing that rebuilt drive on the press when returned, it was a bad rebuild). Since the technology of that drive is so old the cost to rebuild was 40% more than buying a new Siemens. I bought 2, one for back up. That Siemens drive being installed started this whole mess.