Capacitor Start or Permanent Split Capacitor?

What kind of printer is it? Most printers these days use steppers (to get the precision & variable feed rate needed for graphics etc.)

Really no way to answer your question . . . Information seems to not be consistent with printer motors, which are usually stepper motors these days, if not closed-loop BDC's or servomotors.

Do you have a printer model that might be useful in helping those of us who may be able to give you some help?

Sorry,

The printer in question is not like a printer for a desktop computer it's more like a table top label press. I was in a bit of a hurry when I typed this up this morning.

The motor is the rewind motor and is currently switched on and off by a photoelectric switch. The switch senses a loop in the paper running through the press and turns the motor on and off constantly as the press runs, and the motor runs the rewind spindle.

What I am trying to do is vary the speed at which this is done to create a smoother run motion. The motor has 2 small capacitors hooked, I believe, in series. I have no wiring diagram as the machine is very old and the wires are in a very tight spot.(cant see them)

I have already modified the main drive motor and have added some additional processes to it. Thus the need for the variable speed rewind.

Again Sorry for the confusion. I am more trying to identify the type of motor than anything else. I am familiar with a capacitor start ac motor, and typically the cap has been mounted on the motor housing, although I have seen them the other way.

The Permanent split capacitor motor is the confusion for me as I am not familiar with the operation of this design. If indeed the motor is a PSC then I can use the drive I have in-house. If not then I need to replace the motor. I just don't know how to tell the difference.

Kinda like a big DUH on my part!

Reading and re-reading these posts, it seems that the crux boils-down to:

? "What is the difference between PSC & Cap-start design?"

When dealing with motors of the size/type that you have, capacitor-start design uses a cap (usually 'paper-type'/high mfd) in series with the start winding for extra starting torque, AND includes either a centrifugal* or electronic switch to drop the start winding OUT of service after reaching about 70-80% of full speed. The PSC design has usually an oil-filled (low mfd) cap in series with the start winding, and these windings remain energized continuously while running. This means that for any given number of poles, a PSC design will have a slower running speed than an equivalent cap-start design.

Certainly, more can be added here, but if I'm on your wavelength, this is all you needed. [Unless, of course, you have a 'hybrid', Cap-start/Cap-run motor...?]

* with the age of your machine, rest assured it would be a centrifugal-type switch!

Regards ~

I believe you are indeed on my wavelength here.

Now I am fairly certian I have a psc design here.

I have one additional question.

If i put a variable speed control in line with this motor do i put it between the motor and caps or before the motor and caps?

If you can see the wires in the connection box that are going to the caps, then it isn't likely a PSC motor. If you can see an access plate on one end of the motor bell housing (where the shafts are), that would indicate a centrifugal switch, meaning it is not a PSC.

Hi double i b,

We had an old labeling machine that used an AC motor and a switch that sensed a long loop in the web to operate a rewind spool. To save changing out motor contactors/relays, we just installed a spring adjustable slip clutch with a felt disc so you could adjust the web tension of the rewind spool and just got rid of the switch so the motor ran constantly. Problem solved and it ran great for years.

Just a thought.

Jeff

Excellent thought sounds like a plausible fix for my problem I will look into that.

Replying HERE to your question in post 7... I would look at snygolfgs's option (post4), because the speed of the PSC motor is "set" by the number of poles (wound on the stator) and the line frequency. You would need to have some custom re-winding done in order to vary the speed at all ... and then, only by switches, as in a ceiling fan ... and your overall performance probably wouldn't be up to the task any more. [The capability of any rewind would be limited by the slot size and available iron...]

Best of luck to you ~