VFD derating 3

[itsmoked]

I have a VFD that I have to derate because of its sissy temp rating. It has to be put in an enclosure and if the air temp in the enclosure exceeds a mere 104F/40C I have to derate the drive to 80%. So it's a 25HP motor stating 29A I'm using a 30HP (47A)drive.

How do I have to rate the wiring and protection. Do I have to scale that all up when I'm only actually using the drive's larger semiconductors and heat sinking and none of the drive's larger HP capability?

Any chance I can rate it all against the motor's name plate FLA?

I can image the answer... Code answer always = sux.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Bill West; Thanks much for running the BTU game. I looked at that Etool box page and saw "sensible heat" and that made me groan and I couldn't bring myself to work that out. So thanks. Yes, not a 100% duty cycle. PLUS! I have upped the drive size, note the 30hp drive for a 25hp motor so technically I get another 10C of funness. (122F)

I have to wait for waross to sober up or maybe he got bucked off Bandit and lit on his head.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FacEngrPE]

Drive Fuses - per this document

https://www.files.bgbsupply.com/bgbsupply-files/Bline Fusing WP.pdf

the purpose of drive fuses is to prevent the explosive disassembly of the IGBT (or other solid state) switch. Explosive disassembly likely would result in a 3 phase arcing fault letting all of the magic smoke out.

As long as the environment is clean enough, blowing air through the cabinet is a simple way to cool a drive. Another option is to select a drive that places the heat sink on the outside of the enclosure. Automation Direct has some drives that can be mounted this way

https://www.youtube.com/watch?v=k4PuHo2BkTU&feature=emb_rel_end

The drive you have might have a flange mounting kit available.

Fred

 

[jraef]

Fan forced ventilation, although fine for many applications, is not recommended for outdoor installations, especially anything near the coast. Introduction of moisture and contaminants and in particular, salt spray, is the ticket to a slow (or fast) march to death. For some, if it lasts a year or two they are happy, but if you expect it to last for 5 years with a costant buildup of crud on the sensitive bits, good luck.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[itsmoked]

consider an outside the enclosure thermostat and let the fan run continuously when the ambient air rises above a certain point.

Great idea! Though I've got no good way to put the thermostat externally. I will mount it right at the box air inlet so it should be seeing the ambient.

Keith Cress
kcress -

http://www.flaminsystems.com