Drive heating elements with a VFD
Drive heating elements with a VFD
(OP)
Long story, but I am working on a little R&D project that requires a immersion heater total draw of about 50 amp.
The heater will be installed where there is normally a large extrusion pump. There is a VFD wired to the pump via plug/recepticle.
Question is can I drive the immersion heater with the VFD that normally controls the pump?? I have asked three people and no-one has a definative answer. My gut tells me no, but I also don't want to spend a big chunk of money to wire something for a one-time test.
If it would work, how would the frequency from the VFD affect the resistant heater elements?
Obviously I'm not an EE :)
The heater will be installed where there is normally a large extrusion pump. There is a VFD wired to the pump via plug/recepticle.
Question is can I drive the immersion heater with the VFD that normally controls the pump?? I have asked three people and no-one has a definative answer. My gut tells me no, but I also don't want to spend a big chunk of money to wire something for a one-time test.
If it would work, how would the frequency from the VFD affect the resistant heater elements?
Obviously I'm not an EE :)





RE: Drive heating elements with a VFD
Another solution is to by-pass the VFD and use the existing cabling to feed the heater.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Drive heating elements with a VFD
RE: Drive heating elements with a VFD
Yes, it is possible. We have supplied a few thousand drives to an OEM who wanted to use the vfd to control heating elements. As Gunnar points out, V/F (scalar) control is necessary not 'vector' control. Higher PWM switching frequencies are typically required so this will sometimes put additional stresses on the VFD so be aware of any derating the VFD manufacturer stipulates on the current rating.
RE: Drive heating elements with a VFD
Just curious as to why higher switching frequencies are required?
RE: Drive heating elements with a VFD
I'll post the results if we decide to go this way. It is probably more likely that we will pull the VFD temporarily and install a controller that is more predictable and matched to the heating elements. (but still use the existing wiring).
RE: Drive heating elements with a VFD
They were in this particular case due to the design of the heating elements. I'll be honest, I can't recall why (it's about 6yrs ago now) but I do know that <6kHz and we seemed to have a few problems with the drive we used. I think 12kHz was the optimum switching frequency and this put other considerations into the cooling of the drive.
RE: Drive heating elements with a VFD
Any comments Gunnar, is this reasonable or am I about to learn something new?
respectfully
RE: Drive heating elements with a VFD
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