# 50 HP Motor



## JDHElectric (Oct 7, 2010)

Got a call tonight about two 50hp motors that are running printing presses for a local newspaper. They say periodically the presses will slow down and/or speed up during a run. Anybody got any insights as to what might be causing this?


----------



## RIVETER (Sep 26, 2009)

JDHElectric said:


> Got a call tonight about two 50hp motors that are running printing presses for a local newspaper. They say periodically the presses will slow down and/or speed up during a run. Anybody got any insights as to what might be causing this?


Sales are intermittent.


----------



## JDHElectric (Oct 7, 2010)

rivet LOL, with a local newspaper I would say that could be the case but i think its doing it when they are trying to run the next day's paper at night....any REAL ideas out there?


----------



## Jlarson (Jun 28, 2009)

Are they started across the line?


----------



## RIVETER (Sep 26, 2009)

JDHElectric said:


> rivet LOL, with a local newspaper I would say that could be the case but i think its doing it when they are trying to run the next day's paper at night....any REAL ideas out there?


Glad you caught the joke...I meant no harm. Is there possibly a large load within the plant that periodically cycles, causing a "lower voltage" situation?


----------



## JDHElectric (Oct 7, 2010)

not sure if they are across the line or not, no other loads I don't think that would pull the voltage down but we will check. they are running and this is only happening every 2-3 days not daily. just wandering if anyone has any experience with slow down or speed up and what may have been the problem?


----------



## Wirenuting (Sep 12, 2010)

Could be a Freq drive going out or bad connection in the starter or motor. 
If it's a size 3 starter with a 2 stage start, check the inline resistor bank. One could be going soft and getting ready to snap. 
Open the door to the bucket and take a look for over heating. But if it has a resistor bank, don't open the door if it's energized. The bank could be bowed and sitting just off the door. And we all know how you sometimes need to press in on the door as you defeat the interlock.


----------



## Wirenuting (Sep 12, 2010)

Here is a SquareD one I just gutted last week when I installed a new drive to replace the one on the far right. 
You can see the three open resistors. 

Had another last month on a fire pump. That one bowed almost to the door as she heated up. It got cherry red as the pump fired and flexed outward. 

Good luck.


----------



## K2500 (Mar 21, 2009)

JDHElectric said:


> not sure if they are across the line or not, no other loads I don't think that would pull the voltage down but we will check. they are running and this is only happening every 2-3 days not daily. just wandering if anyone has any experience with slow down or speed up and what may have been the problem?


A/C or D/C motors? Control set up?


----------



## eric7379 (Jan 5, 2010)

JDHElectric said:


> not sure if they are across the line or not, no other loads I don't think that would pull the voltage down but we will check. they are running and this is only happening every 2-3 days not daily. just wandering if anyone has any experience with slow down or speed up and what may have been the problem?


In the past printing presses would have DC motors for the drive motors. Depending on how many printing couples and towers you would have would determine how many motors you would have. Modern day presses typically have AC drives and are mostly direct drive, meaning that there is no line shaft. A few questions:

1) Is the press direct drive or is there a line shaft?
2) If there is a line shaft, does the entire press speed up and slow down, or is it just the printing units or just the folder(s)? 
3) This might not be electrical at all. If there is a line shaft, there is a possibility that it might just be that the drive belts are slipping. Another mechanical possibility is there is a clutch that is going bad or possibly a drop down drive. I have also seen where the keyway on the gears and/or the shaft is worn to the point where there is constant slippage.
4) Are there any kind of meters on the drive panel doors? Armature amps? If there is, what are the meters doing when this is happening? 
5) Does the fold go way off or the circumferential register go way off when this happens? 
6) If these are DC motors, what about the brushes? Commutator?


----------



## eric7379 (Jan 5, 2010)

Another possibility to help you and the customer solve the problem, has anybody changed a bunch of rollers recently in one of the units? If they are set too tight, this could be causing a lot of drag but I highly doubt this would be the case because the rollers do not last very long if they are set too tight. They let their magic smoke out after the press runs at speed for 5-10 minutes.


----------



## MDShunk (Jan 7, 2007)

This is one of those things that you could spend a ton of time trying to troubleshoot. First thing's first... determine how the motors are started, then determine what sort of speed control arrangement is in place. In my mind, if the motors only "sag" in speed, I'd look at starting equipment. If the motors slow quite remarkably, I'd look more at speed controls. I don't have much personal experience with conventional printing presses for newspapers and such. My experience is all with Heidelberg presses, and they're a little different animal.


----------



## varmit (Apr 19, 2009)

This is a problem that could have numerous causes. Usually on these type presses, one motor is the master and the other motors are slaved from the master for speed matching. Sometimes there is one speed reference that goes to the main motors and there are dancers to adjust the speed matching.

If these are DC motors:
Check the brushes for wear and spring tension.
Check for excessive carbon buildup on the armature.
Check the motor field source.

If these are AC motors:
Check the fault buffer, in the drives, for recent faults.

For AC or DC:
Check for equipment mechanical changes or wear.
Check any mechanical brakes or clutches.
Has the line speed been increased from a previous setting?
Is the unwind speed adjusting properly to the press speed?
Check terminations, both power and control.
Many, many possibilities.

This sounds as if it COULD be a mechanical overload of the drive system and the drive(s) are going into current limit. If this happened, it could cause a drop in line speed until the load on the drive was reduced back to within operating limits, then the line would go back to the commanded speed. BUT, IT COULD BE OTHER ISSUES

Good luck. Plan on some time to find this.


----------



## frenchelectrican (Mar 15, 2007)

The other possiblty espcally true with older conventail press if you have DC motours check the tachometer motours to make sure they are good shape and check the V/ RPM raito to see if liner or hit a bump if that the case it may affect the drive system.

And also check the POCO supply to see if you have any recent surge or dips { most common curpits typically capaitour banks switch in or out. }

I know it will not be easy to find interment trouble but you will find it one way or other.

If this is a AC motor with AC system somecase you may get feedback loop drooped a little so check that as well.

Merci,
Marc


----------



## RSmike (Jul 31, 2008)

If you have access to a power quality meter you may want to rule out the power company. It's at least something you can put in place and not have to sit around and wait for something to happen.

There's always the "Norm factor". Norm doesn't like to work too hard and has access to the speed control. Every plant has a "Norm Factor"; Just with a different name. 

RSlater,
RSmike


----------

