ConvertingQuarterly.com > Drives for Web Handling

28

Shaft Currents

Posted by Clarence Klassen on November 28, 2011

Most motors used with Variable Speed Drives have some degree of shaft current induced in normal operation. That is the spinning rotor in cutting lines of flux, induces some voltage on the shaft. Stray capacitance puts voltage onto the shaft each time the VSD switches. If a loop through ground exists...

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20

Detecting Roll Slip

Posted by Clarence Klassen on June 20, 2011

With enough torque, web slipping past a roller is inevitable. I have seen web slipping on paper machine forming sections, coating rolls and many other places. Slippage occurs when the forces on the web exceed the traction available between the roller and web. Slippage can be aggravated by wet surfa...

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Posted in: Drives, Faults, Design

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13

Stalled Motor Fault

Posted by Clarence Klassen on June 13, 2011

The Stalled Motor fault is a common cause of drives tripping out in web handling applications. A stalled motor is usually serious. An example would be if an extruder faults on stalled motor. This could be because the resin is not melted or the screw is damaged. While threading the line, the line sp...

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Posted in: Faults, Design

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11

Torque Limit

Posted by Clarence Klassen on April 11, 2011

Torque Limit is a drive function that limits on the torque the motor can deliver. The motor itself does not control its own torque, but will strain with all its might to keep speed at its setpoint. This is often up to 500% of the torque we would calculate from the motor nameplate. 500% torque could ...

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21

DC Bus Over Voltage

Posted by Clarence Klassen on March 21, 2011

AC Drives are fed by AC mains and produce an AC power output for the motor. Why then is “DC Bus Over Voltage” one of the most common faults on a drive system? It turns out that most of the Variable Frequency Drives (VFD) used in web handling convert AC mains to DC using a rectifie...

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Posted in: Drives, Faults, Maintenance

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21

Stall Tension and Tach Loss

Posted by Clarence Klassen on February 21, 2011

It’s too bad the drive is more important than the web. One common drive fault on many drives used for web handling is tach or encoder loss. This may also be reported as a motor stall fault. As web handlers, we would like to establish tension at the winder or unwind, forget it and get down to ...

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Posted in: Drives, Faults, Turret Winders

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