NickParker
Electrical
How is the insulation made different for VFD motors from the DOL starter motors (General Induction Motors)?
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Insulation for VFD fed Motors
- Thread starter NickParker
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Meaning the installation of the motor itself? Nothing, presuming that the motor is CAPABLE of being operated from an inverter and having its speed reduced. There are MANY issues in that regard, but that’s not what you asked and it is complex.
Next is the WIRING from the VFD to the motor. That too is a complex subject and any answers can only come after fully understanding ALL of the particulars.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
Next is the WIRING from the VFD to the motor. That too is a complex subject and any answers can only come after fully understanding ALL of the particulars.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
Jeff he said i n s u l a t i o n not installation.
Nick; Insulation is provided as "qualities". At one time there were lots of different 'qualities' out there being used. VFD driven motors were failing because in some installations, especially with long VFD to motor lengths, standing waves generated by the VFD would cause overvoltages that could take-down lesser insulation systems. Motor makers soon found they could pad their wallets by using a premium insulation system which cost a little more and charge a LOT more.
However, with VFDs becoming ubiquitous lots of motors were being subjected to these over-voltages and failing. Likely this caused lots of warranty battles. Eventually the price of premium insulation systems came down enough that there was no point in makers bothering with the expense and hassle of using multiple system qualities and they pretty much use premium systems on most of their motor offerings.
Because of this most motors you purchase probably don't have any difference in there insulation systems. This is especially true of motors in the 200V class because they get the same insulation system as the 400V class motors these days.
I almost never use "VFD rated motors" and have never ever seen a motor fail due to VFD voltage issues. Granted I don't see as many as jraef does. I see them failed for lots of other reasons like abuse but not due to the insulation breaking down.
Keith Cress
kcress -
Nick; Insulation is provided as "qualities". At one time there were lots of different 'qualities' out there being used. VFD driven motors were failing because in some installations, especially with long VFD to motor lengths, standing waves generated by the VFD would cause overvoltages that could take-down lesser insulation systems. Motor makers soon found they could pad their wallets by using a premium insulation system which cost a little more and charge a LOT more.
However, with VFDs becoming ubiquitous lots of motors were being subjected to these over-voltages and failing. Likely this caused lots of warranty battles. Eventually the price of premium insulation systems came down enough that there was no point in makers bothering with the expense and hassle of using multiple system qualities and they pretty much use premium systems on most of their motor offerings.
Because of this most motors you purchase probably don't have any difference in there insulation systems. This is especially true of motors in the 200V class because they get the same insulation system as the 400V class motors these days.
I almost never use "VFD rated motors" and have never ever seen a motor fail due to VFD voltage issues. Granted I don't see as many as jraef does. I see them failed for lots of other reasons like abuse but not due to the insulation breaking down.
Keith Cress
kcress -
Oh. In the words of Roseanne Rosannadana... “Never mind...”
The magnet wire insulation has a higher voltage rating. In the past, motor winding insulation was supposed to be 2x the line RMS rating. So a 480V motor would have 1000V insulation. In some cases motor mfrs in North America would just use 1200V insulation so that they didn’t need to use different magnet wire for 460 or 575V motors. But inverters can cause standing waves that reflect back and forth between drive and motor, building up as it does until it can easily exceed 1200V. So NEMA and IEEE came up with a design standard calling for inverter rated motors to use 1488V as the MINIMUM design standard for magnet wire. But subsequent investigations have found that under certain conditions, the spikes can reach up to 3x the DC bus voltage, so on a 480V drive that is 2150V. So many wire suppliers exceed that minimum spec, the result being that 2200V has become very common and I have seen some up to 3000V.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
The magnet wire insulation has a higher voltage rating. In the past, motor winding insulation was supposed to be 2x the line RMS rating. So a 480V motor would have 1000V insulation. In some cases motor mfrs in North America would just use 1200V insulation so that they didn’t need to use different magnet wire for 460 or 575V motors. But inverters can cause standing waves that reflect back and forth between drive and motor, building up as it does until it can easily exceed 1200V. So NEMA and IEEE came up with a design standard calling for inverter rated motors to use 1488V as the MINIMUM design standard for magnet wire. But subsequent investigations have found that under certain conditions, the spikes can reach up to 3x the DC bus voltage, so on a 480V drive that is 2150V. So many wire suppliers exceed that minimum spec, the result being that 2200V has become very common and I have seen some up to 3000V.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
LionelHutz
Electrical
These days, I doubt you'll find many motor manufacturers using different wiring insulation for their "VFD rated" motors compared to their standard motors. If anything, more care is taken during the winding process to properly separate the phase windings. Care can also be taken to ensure each coil winding doesn't have the start and end coils beside each other.
I put VFD rated in quotes because there is no real standard that defines a VFD rated motor. Putting that statement on the motor can mean anything. As an example, the WEG distributor in Canada stocks the standard WEG motors and if you want a VFD rated motor they rivet the tag onto it for you. Probably charge you extra for the VFD rated motor too.
I put VFD rated in quotes because there is no real standard that defines a VFD rated motor. Putting that statement on the motor can mean anything. As an example, the WEG distributor in Canada stocks the standard WEG motors and if you want a VFD rated motor they rivet the tag onto it for you. Probably charge you extra for the VFD rated motor too.
Round magnet wires for VFD duty motors have a special enamel coating to withstand high dv/dt. And they are pricier.
Muthu
Muthu
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