Mentor-2 Drive Zero Speed Problem

Hello Experts,
i am new to this forum,
we have control techniques mentor-2 DC drives for Conveyor application,
Q.1) in motor standstill condition motor not showing zero speed feedback,
it shows zero speed feedback only when we set keypad to 1.11 or 3.13 visualization (we don't understand why this is so- pls give suggestion on this ).

Q.2) in other application when drive stop and start again motor not rotating & drive shows negative speed indication- here when we rotate conveyor once manually (spanner etc) motor start rotating normally (this also we are unable to understand- give some idea on same also.)

thanks in advance.

From where is your zero-speed signal coming? Ideally, it should come from a zero-speed switch on the tail pully shaft of the conveyor (opposite end of the conveyor from the driven end).

If your zero-speed signal is not indicating 0 speed when the motor is standing still, then there is a problem with that signal. It may be generated by something other than the proper zero-speed switch. It sounds like someone has used a signal from the Mentor DC Drive in place of a true zero-speed switch. That may indicate the condition of the drive, but it will never be able to tell if the conveyor belt breaks or comes off the pully.

Hello Lancie1,
we have used zero speed feedback from drive inbuilt output, same zero speed LED also available on Mentor-2 keypad.

I am not familar with your model, but it sounds like the Zero Speed output is being "calculated" by the drive electronics. If you want to know positively that the conveyor belt is not moving, you need to add a Zero Speed Switch that looks at the shaft rotation of the conveyor.

You cannot expect a DC drive using only armature feedback (no tach or encoder) to know with any precision when the shaft is stationary. If you do have a tach or encoder, those should report zero speed correctly.

In a previous life I used Mentors & Mentor II's a lot - used on extruder drives and conveyors etc. We always used them set to either tacho feedback or encoder feedback although in an emergency, AVF was suitable to get the conveyor or bit of plant running.

What Mentor II are you using?. Single quad or 4 quad?. What means of speed feedback are you using?.
If you are using AVF as your means of speed control, you will need to set the zero speed threshold (para 3.23 I think it was) so the drive knows when it is stopped. Remember AVF will give an error of around 2.5% (according to control techniques anyway). AVF speed control can be ok but needs a little bit of tweaking to get running well.

You need to sit down with a Mentor II drive manual and go through the settings - menu 1 is speed reference and menu 3 is all about feedback selection and speed loops. You need to look at these to see if they are set up for your drive and how you want your drive to control it's speed. (assuming all the other vital parameters are ok eg current limits, ramps etc).

If you need total accuracy then you will need an encoder or tacho.

Bolty.