from the SFPM department...
analog speed control
 Posted by Telsafan on 1 June, 2012 - 1:30 am
looking for best idea to control motor speed. I have an inverter driven shaft winding up material on a roll. I am applying a coating onto material and need to control speed by SFPM to maintain coating thickness. as roll gets bigger sfpm increases, so I need to slow the drive proportionally. I'm using a red lion frequency to analog module then red lion analog signal inverter to output to drive to slow down as roll gets bigger. problem is SFPM still increases??

 Posted by bob peterson on 1 June, 2012 - 9:52 am
This is a fairly common center winding application.

You will need to calculate the circumference and relate that back to the desired RPM of the motor so that the surface speed of the film stays the same.

--
Bob

 Posted by telsafan on 3 June, 2012 - 1:14 pm
> This is a fairly common center winding application.

> You will need to calculate the circumference and relate that back to
> the desired RPM of the motor so that the surface speed of the film stays the same.

Thanks Bob, I have calculated circumference both min and max and set the max signal on a red lion ifma to 10v = 14.250 Hz provided by a monitor roller running at 24 rpm then to an iama signal inverter to send 1 volt to drive. speed control should balance at 5 volts giving a stable 12 rpm. problem is sfpm still increases from min diam to max diam. As circumference increases volts to drive decrease which should maintain my 12 rpm at monitoring roller but it don't. it increases still.

 Posted by Bob Peterson on 3 June, 2012 - 2:05 pm
Your RPM control signal has to be inversely proportional to the circumference of the roll. I don't see how what you are describing actually does this.

 Posted by telsafan on 15 June, 2012 - 10:12 am
> Your RPM control signal has to be inversely proportional to the
> circumference of the roll. I don't see how what you are describing actually does this.

thanks again bob
my rpm signal comes from a prox monitoring the teeth on a sprocket which is on a idler wound thru in the path. As the circumference increases the signal increases and then is inverted out to drive which should hold constant speed from signal?

Thanks
Telsafan

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