Can we measure O/P voltage/current with ordinary multimeter? Under what conditions will the standstill current of motor exceed rated value assuming there is no mechanical jamming. This gives torque high alarm.

We are using Seidel servo motor ( 6-sm56-3000 ) and Kollmorgen servodrive servo star 606 for position control application. We very offen face problem of torque high indication even when the motor is not operated. You just try removing the detachable connectors in the field and some times the problem goes off and some times it doesn't.

There are no permenent open circuit/short circuit in the cbale run, the problems are faced once in a week. The mysterious appearence and vanishing of problem is a real concern to all of us.

Dear friends can you help ?

Regards

 

I don't know how that particular motor is commutated but most servo motors have a device for timing the transistors in the drive. The general idea is that of a car. Your distibutor rotor spins inside the cap making sure that the appropriate cylinder or in our case section of the motor winding fires at the right time. If the tach or encoder that is providing this timing signal to the drive is for some reason intermittantly failing to make it to the drive then it could cause weird standstill/motion vibrations or to a lesser degree high torque in 1 or many spots at a standstill. I have assumed that you have eliminated any physical reason why you have the high holding torque like lack of lube or bad ways or ballscew or whatever the mechanics may be. [email protected] Torque command is calculated is based on many things but I would take a look at the command versus actual or lag a little more.

 

We had problems with Seidel servos and Kolmorgen drives as well. I understand this is about positioning, what kind of positioning are you talking about? Is the position command given through the inputs of the drive or is it comming from a PLC? (I ask this because in our case there was a problem with the firmware loaded in the drive and in this case you should contact Kolmorgen. On the other hand you should ensure yourself not having any other problems like EMC, that can be a cause gor disturbances on your cables and cause a higher current to be consumed from your drive, so that an overcurrent occurs. Also check the specifications for cablelenghts. Give me some more details on your installation and maybe I can help you out.

Greetz

 

One way I could see this happening - if you have a
brake on your system and it is strong enough to hold
the motor at full torque - if you give a position
command to the drive and it is even a few counts off
of commanded position, then over time the integral
term in the PID would wind up until you were sending
out full current and/or faulted the drive.

Other potential problems include firmware issues, EMF,
etc. If at any time you have overloaded the drive you
may have stressed a component on the drive and it may
now be failing at a level much lower that that at
which it was rated.

My $0.02 - I have not used the Seidel servos, but have
used Servostar drives in many applications with no
probs (and no, I am not affiliated in any way with
Kollmorgen).

Davis Gentry
Delta Tau Data Systems