Simoreg DC Master drive problem

[Dbeauvais]

cjd1965,

I called someone and they said if this was wired in parallel it would be for dual voltage. I guess the namplate could be wrong. The manufacturer has the motor numbers so hopefully that could be checked. This motor never even needed a set of bearings for 11 years. The only time it was out of the building was to turn the comutator, change the bearings and clean it. That shop reported the field as good but when I asked for the report there was none, so it was checked but all verbal. The schematics do not show anything and the man told me this was common so that the motor would go back to Thrige-Scott for repair work.

 

[Dbeauvais]

DickDV,

Well, your email certainly describes what happened here. The electrician comes in and does not verify the field resistance, takes 360V divided by 5.94 amps and proceeds to set up the drive for those conditions. We have sudden heat and overshoot issues. Then they come back and now they are checking the feild and set up drive number 2 with new parametrs . . . and running sweet since. The schematic and nameplate not showing this is actually dangerous.

 

[Dbeauvais]

DickDV,

Is there any kind of internal test I can perform to verify how the motor is wired?

 

[DickDV]

You can check out the leads in the motor junction box. A complete list of the leads and their ID labels would be good info.

 

[Dbeauvais]

DickDV,

I do not know how to add an attachment to this reply, I wanted to show you a PDF on the motor's nameplate. Although the press manufacturer has not heard back from Thrige-Scott yet the plate says, "Winding - Shunt". From what I have read doesn't shunt mean the field windings are parallel to the armature windings? I have also read that there are 3 types of DC motors; series, parallel and shunt (yet shunt appears to be parallel). That nameplate had to have something on it to warn any electrician or motor shop before doing anything.

 

[DickDV]

A DC motor will generally indicate the field configuration on the nameplate. The common types are Series, Shunt, Comp.Shunt, and Stab.Shunt.

Series fields are designed to be wired into the armature circuit so there is only one circuit with the armature and field in series with each other. These motors are usually used for traction applications (locomotives, mine trucks, fork trucks) and are unstable, difficult to manage motors. Except for centrifuges, they rarely appear on industrial machinery.

A shunt field motor has the field circuit as a completely separate circuit. It requires its own power supply and has a relatively low current, high inductance coil design. It is used for industrial machinery especially where the machine must operate in both directions. It does not have a particularly strong overload torque characteristic.

Comp (Compensated)shunt and Stab (Stabilized) shunt fields are both compound wound motors. That means that there is both a series and shunt field. The two fields are wound on top of each other so they are magnetically linked but not electrically linked. The series field is wired into the armature circuit while the shunt field has its own circuit, power supply, and low current design. These are really shunt field motors but the series field is in there to add extra overload torque. The Stabilized Shunt design adds only a little extra and the Compensated shunt adds somewhat more. These motors are often found in industrial machinery too especially where heavy overloads are encountered. The key drawback to a compound wound motor is that it is directional. By that I mean that the available torque is more in the forward direction than in the reverse direction, or vice versa. The determining factor is how the series field is wired into the armature circuit. In one direction, its magnetic field adds to the shunt field while, in the other direction, it subtracts.

The result is that compound-wound motors are usually only found on non-reversing machines like extruders. I suppose a printing press that never backs up would be another possible application.

It is critical to know what kind of motor you have and, if a compound-wound motor, what the two field orientations are for the direction you intend to operated in. I've seen numerous motors with the series field wired backward and they sure do run strange. Lots of amps and very little torque! And very poor speed regulation too!

 

[Dbeauvais]

Thanks for the lesson DickDV. I should here from the manufacturer today.

 

[cjd1965]

cjd1965,

I called someone and they said if this was wired in parallel it would be for dual voltage.

Hi Doug
This is true, but would depend on how the couils were wired.. series, parallel etc. How are you enjoying the learning curve?

Cheers

 

[Dbeauvais]

Yes, I have actually. Anytime I learn something it is good. In the old days it would be very difficult to find this many professionals to advise you all at once. Although the Internet may ultimately be my demise (book printer), it certainly has made many things easier. I'm still waiting on Thrige-Scott for answers though.

 

[leitmotif]

I was hoping for some hard numbers and a good description of motor before saying anything.

Everyone has now gotten worried about the shunt field and approx 6 amps at 300 VDC - HOWEVER
no one has mentioned at what RPM.
Also how drive is controlling speed. IS shunt field volt and current held constant and drive regulates armature voltage and current??

The facts as I understand
April 08 motor sent to shop for commutator cut bearing change and minor work.
Everything is fine until
May 09 motor control problems
Drive changed out
Still problems
Put in another drive??? I got lost about this stage.
French motor guy says motor OK

I would guess that the whole issue comes down to
1. Too many chefs in the stew
2. Lack of training for inhouse staff. They only deal with this once every ten years so it is hard for them to stay expert at it.
3. Lack of manuals on how motor is put together and connected
4. Lack of good relationship with good quality qualified motor shop.

At this stage I would want a full set of schematics on how that motor is connected. I would want a chart for motor operation at 5 or six speed settings that shows armature volts and amp and shunt field volt and amp and if they are installed winding temps. I think if only for sake of completeness and to ensure no one can question I would also want AC line volt and amp on all 3 phases at each RPM setting. All of these readings would be taken at soonest opportunity with the machine in normal operating mode and FOR SURE I would have a set of readings for printing and with what ever stuff loads the machine down most.

I would still install voltmeters and ammeters on armature and on shunt field.

Each shunt field pole is designed to operate at X volts and Y amps. It is very possible that motor is designed to allow shunt field connections for two different DC line voltages ie 360 and 180. Properly connected for the desired line voltage they should draw the "ideal?" 5.65 amp (was it??).

The only nagging thought in my head is what if one field pole is connected backwards ie N is S and S is N. Current should be just fine in this case. I think though one backwards field pole would greatly decrease motor performance.

I estimate the field is properly connected because
1. It has not burned out yet
2. The motor has run just fine for a year out of the last overhaul.

I think the motor has been just fine all along and most of the problems were drive related.

Dan Bentler

 

[Dbeauvais]

Dan,

The company is not large enough to have an in-house motor expert. I'm still waiting for Thrige-Scott to confirm motor wiring (it has taken too long). The French guy's gut told him the motor was fine but left a 1% chance that he could be wrong. He based that on how well everything was running. I'm having maintenance ohm out the motor weekly to make sure nothing is spiraling downward.

Here's the nameplate info:
Bk 200W
Winding Shunt
56 Kw
1500 RPM
Arm - 460V 134A
Exct - 360V 5.94A
Rating S1 Class F
Enclosure 1p 23 ******t 40C
Required cooling 1c 0 6

Here's the report from the French electrician
Test motor for ground: good
Test coil resistor: good
Ran motor full speed: good
Ran motor low speed: good
Armature looks perfect on comutator, no arcing
Motor running at 38C
Cooling fan: good
(motor spec on coil 360V at 5.94A, by formula ohms = 60.6 my reading is 30 ohms ohms, coil may be connected parallel)

Nothing is wrong with motor.

The schematics did not detail the motors wiring which does not make sense. I do not think the 5.94 amps were holding steady on both warm and cold motor.

It's all too logic that the 1st drive's parameters were wrong causing all the problems. Then when they came back the first thing they did is what they should have done the first time, check the field resistance. The 2nd drive was installed with new parameters and the motor has been purring like a cat since. I would feel a lot more comfortable with the Thrige Scott wiring information.

Doug

 

[leitmotif]

Dan,

The company is not large enough to have an in-house motor expert.
REPLY. No of course not - you are not a newspaper who buys ink by the railcar. You guys make money printing not motor repair. It is hard to stay expert on this stuff if you only have the need every 10 years. Even large newspapers probably keep a drive expert on "retainer".

Here's the nameplate info:
Bk 200W
Winding Shunt
56 Kw
1500 RPM
Arm - 460V 134A
Exct - 360V 5.94A
Rating S1 Class F
Enclosure 1p 23 ******t 40C
Required cooling 1c 0 6

REPLY GOOD STUFF KEEP IT.

Here's the report from the French electrician
Test motor for ground: good
Test coil resistor: good
Ran motor full speed: good
Ran motor low speed: good
Armature looks perfect on comutator, no arcing
Motor running at 38C
Cooling fan: good
(motor spec on coil 360V at 5.94A, by formula ohms = 60.6 my reading is 30 ohms ohms, coil may be connected parallel)

REPLY Wish he had taken some volt and amp readings but if the motor is running fine and at 2 degree less than spec'd all should be good.

I think I have explanation on field resistance.
French guy report read
Test coil resistor: good
Is this a resistor in series with the shunt field??
That would explain the 30 vs 60 ohm shunt field resistance question
DEPENDING ON where you took the readings.

OTHERWISE
Take for example
DC motor reads .1 ohm on leads. Line volt 250. So theor current is 2500 amp (it may very well be that high instantaneous on start). But current is say 10 amp on run - why? All motors are generators and all generators are motors. While motor runs it is also a generator the generator action also called Counter Electro Motive Force (CEMF) is a counter voltage and in effect reduces line voltage. CEMF is proportional to RPM so at start it is not there and builds with speed.
SO
Effective voltage (just my term) = line - CEMF
CEMF = line - EV
= 250 -(10 amp x .1ohm
= 249 volt.
This is not a real world example. DicDV you have a beter one?

SO for shunt field at 30 ohm and 360 volt
theor amps is 12 BUT run amps is 6. This can be explained by CEMF
at start the field may be drawing 12 amp but
in run it is down to 6 because of CEMF action on shunt field.
DickDV check me on this been too long since DC theory class.

Nothing is wrong with motor.
REPLY From a LONG distance I agree.

The schematics did not detail the motors wiring which does not make sense. I do not think the 5.94 amps were holding steady on both warm and cold motor.
REPLY I would expect shunt current to vary a little say plus or minus 0.1 or 0.2 A due to warming other factors and regulation of drive.

I would feel a lot more comfortable with the Thrige Scott wiring information.
REPLY You will need this stuff in future.

Dan Bentler

 

[allscott]

Wow, just read this whole thread and talk about things going sideways!

SSD's 590 drives are pretty much identical to the old Eurotherms. The power electronics have gotten smaller but everything else is pretty much the same, a lot of parts still swap between them. I've started up 2 of them in the last couple months and am starting up a 400HP unit on Friday.

As far as the rest of this discussion, wow I don't even know where to start.

Dan, your description of CEMF is right but what does that have to do with the shunt field?

A good DC drive guy on site would have had this straightned out long ago. I'd string up whoever decided putting in a new simoreg was a good idea. DC motor drive control isn't something you want to mess around with if you don't know what you are doing.

DickDV, I don't claim to be anywhere near your league of DC drive knowledge but I definately feel your pain.

 

[leitmotif]

Wow, just read this whole thread and talk about things going sideways!

Dan, your description of CEMF is right but what does that have to do with the shunt field? quote]

It would explain the dilemna over the resistance. I do not remember from motor theory MANY years ago if CEMF affects the shunt field. That is why I asked Dick if my theory was right. I am more than willing to ask you also. Especially so when shunt is fed from source other than the armature source ie separate excited.

Dan

 

[allscott]

I'll have to read over more on what is going on to comment, I kind of skimmed everything.

The shunt field is completely seperately excited and CEMF will have no effect on the shunt field readings. Also you can generally set the shunt field up to be either a constant voltage or current regulated. Since its the current in the field that really matters using current control is the prefered method of doing it these days.

I'll comment more when I have had a chance to look at the provided data.