Reversing a DC Master drive

M

Thread Starter

Mat

Hi guys,

I have a 6RA70 DC Master drive.
I have a single normally open contact available from a PLC.
With the contact normally open, I want the drive to run in the so-called forward direction.
If this contact is normally closed, it means the drive then reverse the motor in the opposite direction from the main setpoint. This is an extruder application where such a thing/application is used to remove material being extruded which has accidentally hardened during a drive/system fault and perhaps we need both directions of operation to free the material. I have a jog forward and reverse. I need sometimes to give a bit more umph...

Can someone help me on what parameters I need to program in the drivemonitor program?

Regards
M
 
I'm wondering if you could provide more information, and if it has been customary to run in the reverse direction in this application, or if that is something new. In a typical plastics single screw extrusion machine I can't see the benefit... all that would happen is an attempt to convey material back towards the feed hopper.

> I have a single normally open contact available from a PLC. <

Seems that you need more. Even if the jog forward and reverse are hardwired outside of the PLC you need a 'run enable' signal to tell the drive to energize the output bridge, and, in this case, a direction input - or a minimum of two PLC outputs. If the jogs are outside of the PLC then how are they interlocked so they are disabled when running in normal production mode?

What is used for screw speed setpoint command... a 10 turn vernier potentiometer, an analog output from the PLC, or something else?

>accidentally hardened during a drive/system fault and perhaps we need both
>directions of operation to free the material. I have a jog forward and
>reverse. I need sometimes to give a bit more umph... <

Don't know what you are extruding, but with most polymers it is preferable to soak the extruder barrel at or somewhat above processing temperatures rather than attempt to push it out in a hardened state.

Your allowable 'umph' level is determined by shunt field strength, the drive's armature current limit setpoint, and how fast you are commanding the screw to turn (and hence, armature voltage). If the screw isn't turning due to the polymer turning into a rock, motor is stalled, and motor nameplate full load current is pushed through the motionless commutator for too long you run a substantial risk of "stall marking" it. You might opt to set the current limit higher - 150% of motor FLA for up to about 30 seconds - but now the stall marking risk is even higher.

Be very careful that your desire for 'umph' doesn't result in other undesirable consequences. These may include blowing bolts off between the thrust housing and transmission, or even twisting the extruder screw into two pieces.

> Can someone help me on what parameters I need to program in the
> drivemonitor program? <

You probably should read the manual while pondering your application.
 
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