We have hundreds of drives on hour air handlers with great results. Need to keep them clean as heat kills.gnuuser said:I dont highly recommend using a vfd to drive a fan, or blower due to the fact that loss of power will result in feedback from the magnetic field collapse will create a massive and catastrophic spike back through the vfd and frying it. these setups require a strong clamping circuit. even shutting them down improperly can damage them you are far better off using a rheostat type controller
I don't follow. How does turning off a blower differ from turning off any other motor load?I dont highly recommend using a vfd to drive a fan, or blower
due to the fact that loss of power will result in feedback from the magnetic field collapse will create a massive and catastrophic spike back through the vfd and frying it...
Same here. All of our rtus are on drives, we wouldn't have them any other way. Rheostats are extremely impractical for production facility use.Wirenuting said:We have hundreds of drives on hour air handlers with great results.
For me getting the bosses here to install aux's switches on the local disconnects is like pulling a 5 year olds Tooth. They don't see or understand the reason.ponyboy said:Same here. All of our rtus are on drives, we wouldn't have them any other way. Rheostats are extremely impractical for production facility use. Last batch I hooked up simply require an end switch to turn unit on and off. No problems at all with the vfds
Did 2-700hp id fans on kilns... Installed load side of vfd contactor to disconnect output of vfd cuz on power loss a natural gas engine sarted and turned fan to keep fire going!gnuuser said:I dont highly recommend using a vfd to drive a fan, or blower
due to the fact that loss of power will result in feedback from the magnetic field collapse will create a massive and catastrophic spike back through the vfd and frying it.
these setups require a strong clamping circuit.
even shutting them down improperly can damage them
you are far better off using a rheostat type controller
Gnuuser, most drives these days are design to take large CEMF spikes. There are diodes integrated into the transistor modules just for that purpose. I have heard stories of installers undersizing drives with blowers that then have CEMF problems. A few temperature control systems I have encountered actually have a line contactor turn off the drive instead of using its start/stop controls.I dont highly recommend using a vfd to drive a fan, or blower
due to the fact that loss of power will result in feedback from the magnetic field collapse will create a massive and catastrophic spike back through the vfd and frying it.
these setups require a strong clamping circuit.
even shutting them down improperly can damage them
you are far better off using a rheostat type controller
A 15Hp ,460 volt, 17.7 amp ABB drive, is tripping out on over current. The motor is running a fan in an AHU. I didn't start the diagnoses, but I got pulled in, because right now nobody can find the problem. Originally, the motor megged greater 2.2GΩs. So they replaced the drive, same problem. The motor was then replaced, same problem. Replaced the wire between drive and the motor, same problem. Replaced the drive again, same problem. The drive does not trip right away, but seems like there is a 7-10 day interval, between trips. Could dirty power do this? All lugs at the drive, and in the peckerhead are tight.Any other ideas as to what to look for?
Has anyone looked at the current? Has the mechanical load on the motor changed or is it somehow changing when the trips occur? I'd put a power logger on it and tell the jackoffs in charge to STOP throwing parts at it for the love of god.
Looks like our OP went AWOL on us, too bad. These were the right courses of action, maybe he took a look and discovered, wonder of wonders, that the drive was tripping on over current because.... drum roll.... the motor was drawing too much current too quickly!If it's tripping on overucrrent, what are the current values per phase during a trip? What's the normal running current? Is it belt-driven or direct? Is the plenum shared by any other blowers?
i know what you mean! our tank cooling fans for the molten glass have a blower head of cast aluminumDid 2-700hp id fans on kilns... Installed load side of vfd contactor to disconnect output of vfd cuz on power loss a natural gas engine sarted and turned fan to keep fire going!
Talk about interlocks...
Had a speed sensor that didnt allow vfd to start unless speed was under 300rpm
It was a
Relay nightmare!
All existing stuff we had to interface with!!
Hurry hurry hurry! Time is money!gnuuser said:i know what you mean! our tank cooling fans for the molten glass have a blower head of cast aluminum
they weigh about 1/2 a ton each and act as a big flywheel when power is removed.
we have them sequenced to ramp down when initiating the shut down program but it takes a while to come to a complete stop
our biggest enemy is not power failures but impatient management .
rather than use the shutdown program they will just throw the panel main disconnect![]()