Powerflex 70 Drive

[Guest Jim Heller]

Anyone know if there is a baseline minimum frequency to operate a powerflex 70 drive at continuos operation. Had one fail this morning for the second time. It operates a 15 HP motor, works in a PID and was set up by an integrator with a MAX Freq of 13 HZ.

[Chris Elston 79]

Ouch...how is the HEAT of the motor at 13 hz? What failed? The drive or the motor? I can't see the drive failing, but the motor...yes...You have to have the right kind of 3 phase motor to run it at 13 hz as a norm. I've seen drives fail if a disconnect of main power is abused. Is this drive shut down and power on alot through a main contactor?

[woody308 0]

I have seen continuos failures in the flex family if the ambient temp is too high

[dcorby 0]

Have had many 70 series drives, never had one fail yet. Several run at low frequencies routinely, but not that low. Definitely make sure that the motor is inverter rated, otherwise you could wind up with a problem.

[Guest Guest_Chavak]

Maybe considering forced cooling will help. At 13 Hz the inbuilt fan can't cool the motor effectively, which cause the motor to fail eventually. Chavak _______

[Chavak 2]

Oops, Forgot to log in earlier

[coolhand 0]

Jim, you didn't state what the application for the motor was -pump, blower, drive train, etc., but at 13hz your 15 hp motors' output hp will only be 3.25 hp. If this motor were on a drive train I would change some gear ratio's around to get the frequency back to 40-60 hz. If this were a varriable tq. application such as a pump or blower I would look at changing from a high speed motor to a low speed (if that would work). If it were a blower I would call the manufacture and request a fan performance chart. There you will see that BHP (brake horse power) has a very large effect on a fans output of cfm and static pressure. Simply changing to a lower HP motor and running it faster would get you out of the "frequency hole" that you are in. HP is linear from 0-60 hz. For your motor 0hz = 0 hp, 30 hz =7.5 hp, & 60 hz = 15 hp. After 60 hz hp is constant but tourqe drops of significantly. I try and size my systems to run between 45-60hz. Anything lower than that I feel is too "course" of an adjustment at the drive and not running very efficient. Anything over that and the lack of tourqe makes the load difficult to control. If the load reverses frequently I oversize the drive to help absorb some of that regenerative energy. Lots of things to consider, but I think you will continualy see drive faults at those low settings. My 2 cents Luke PS- let us know what you did and what worked, Thanks!

[darrenj 0]

If the drive is failing..do you have protection on the drive..(Line terminator or a line reactor?) Is the application in the boonies where you will get lots of noise? and as people said the on board fan is usless at that speed..all the low speed apps i come across have a secondary electric fan.. Also whats the duty cycle? if it runs for 2 mins and off for 5 then i dont think its cooling.. If its the drive take a look at the enclouse and ambiant air.whats the temp?? dont know the answers just giving you some questions!!!!!