mylespetro
Member
Hey everyone,
Working on a project replacing a whole bunch of various AB drives (1336, Powerflex 40 etc) with Powerflex 525s. The motors are 3HP on conveyors, so we had specified 3HP drives, but we found out a couple days ago that the original VFDs are 5HP, and also that the max frequency is set to 90Hz, meaning that once the output frequency goes above 60Hz, the drive goes into constant power mode as I understand, decreasing torque to maintain 100% horsepower as the speed increases. I believe at 90Hz we should have 2/3 of the available torque.
I know that it’s common practice to oversize the VFD by one size, but if we were to have used 5HP drives we would have been setting them for a 3HP motor through the parameters anyways, so is there any risk of the drive not having enough torque at higher speeds? My understanding is that the current output available would be lowered to that of a 3HP drive anyways, essentially derating the 5HP to a 3. Just as a side note, we do have the additional fan kits installed so cooling shouldn’t be an issue as far as I can tell.
Thanks in advance!
Working on a project replacing a whole bunch of various AB drives (1336, Powerflex 40 etc) with Powerflex 525s. The motors are 3HP on conveyors, so we had specified 3HP drives, but we found out a couple days ago that the original VFDs are 5HP, and also that the max frequency is set to 90Hz, meaning that once the output frequency goes above 60Hz, the drive goes into constant power mode as I understand, decreasing torque to maintain 100% horsepower as the speed increases. I believe at 90Hz we should have 2/3 of the available torque.
I know that it’s common practice to oversize the VFD by one size, but if we were to have used 5HP drives we would have been setting them for a 3HP motor through the parameters anyways, so is there any risk of the drive not having enough torque at higher speeds? My understanding is that the current output available would be lowered to that of a 3HP drive anyways, essentially derating the 5HP to a 3. Just as a side note, we do have the additional fan kits installed so cooling shouldn’t be an issue as far as I can tell.
Thanks in advance!