Motor drive tripping problems

[vntgpt]

hi,

We use AC motor and frequency drive of same hp rating.
like
AC motor of 10Hp and to drive AC motor we are using frequency drive of 10Hp. Now when we try to run the motor by setting the values in frequency drive as per motor rating, the drive trips frequently after achieving some speed.

In one case, where rating of drive and motor is 7.5Hp we have used gear boxe with ratio being 1:3.5 which reduces the speed from 1440 to 400 approx. but when we try to run the motor on 1440 rpm through drive increasing the rpm gradually so as to have final rpm 400 at the shaft after gearbox, the frequency drive shows the error OL-2 and current motor draws is 20.4 Amps. Please let me know whats wrong. We are facing these kind of problems continously.

 

[jraef]

Far too little information. Don't be stingy, we don't charge by the word (yet)!

The term "OL-2" is meaningless without a description of the fault condition from the VFD manual. Different drive mfrs are going to have different meanings. It could mean an overload of the motor, an overload of the drive, a calculated high motor temperature, we have no idea. It would also be good to know if this happens all the time on this drive/motor? Is this your initial commissioning or was the drive being used somewhere else first? Or was it working fine here but now started doing this? How fast are you trying to start the load? Is it heavy or does it have high inertia? Is it eccentric, as in a cam or weighted flywheel?

20.4A from a 10HP drive (or a 7.5HP, I can't tell from your posting), is high enough to make a motor OL as the prime suspect. Possibilities to look at:
*Friction or binding in the drive train somewhere.
*High inertia as mentioned above
*Incorrect motor connection, for example, it is a dual voltage motor and you are using the lower voltage but have the motor connected for the higher one.
*A short or loose connection in the motor windings, cables or connection box.
I could go on and on really, but it's useless to continue without more information.

 

[itsmoked]

You need to be very careful in sizing VFDs. Unfortunately they are often labeled as xHP but what that means is often the lowest current drawing motor that can be called xHP. You should always check the nameplate motor current against the VFD current rating. Starting with the same HP VFD and then moving up if required. Note too that gear boxes have losses and can increase loads on their motors.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[vntgpt]

vfd is invertek product

 

[itsmoked]

And the model is??

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

If the actual motor current is over the rated motor current you can expect the drive to trip. That's its job. It is supposed to trip when the motor is drawing too much current.
The motor may be too small for the load.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[DickDV]

Please supply the motor nameplate information--in particular, the hp,amps,speed, and voltage. Also, the drive voltage rating,continuous output current rating, and whether the drive is rated 10% overload for 1 minute or 50% overload for 1 minute. That overload rating might be stated as Variable Torque or Constant Torque.

We can help you but we simply need more information.