Class 1 Div. 2 VFD
Class 1 Div. 2 VFD
(OP)
I am looking for a Class 1 Div 2 VFD for a 3 hp. explosion-proof motor. Historically we have used a purged cabinet to house the VFD but I am looking for a cheaper and more compact design. Do you know of any manufacturers? Allen Bradley does not make one.





RE: Class 1 Div. 2 VFD
One word of caution on the motor. An XP rating on the nameplate is NOT enough. The motor must also have XP inverter power labeling. This will define PWM power rather than sinewave, a frequency range, and a current limit. Operation outside these limits violates the UL labeling of the motor.
The above is for North America. I don't know what the rules are elsewhere.
RE: Class 1 Div. 2 VFD
I agree with DickDV.
For regions outside NA, namely Europe, then the ATEX Directive 94/9/EC deals with the safety requirements for equipment and protective systems intended for use in potentially explosive atmospheres.
A word of caution: the use of the words "cheaper" and "explosion-proof" are not a good mix. You can usually remove the word 'proof' and replace 'cheaper' with 'expensive'.
A very useful booklet from my previous paymaster is attached.(it's about 1MB btw)
Any VFD in Europe/Australia will need ATEX approved thermistor input to co-ordinate with the motor. This is a must.
Mounting the VFD in the environment is generally a very big problem and incurs huge cost, whatever the size of the drive. It requires pressurised enclosures with inert gases and is often prohibitive. Look to mount the VFD outside the EX zone.
RE: Class 1 Div. 2 VFD
This is a Class I, Division 2 location. It is my understanding that XP motors are not required by 501.125(B) in the 2008 NEC. The last part of that code section reads:
"In Class I, Division 2 locations, the installation of open or nonexplosionproof enclosed motors, such as squirrel-cage induction motors without brushes, switching mechanisms, or similar arc-producing devices that are not identified for use in a Class I, Division 2 location, shall be permitted."
Does the fact that this motor is supplied by a VFD change this and if so where can I find that in the NEC?
RE: Class 1 Div. 2 VFD
I fortunately have essentially no experience with Div II either.
Sorry I missed that detail in your OP. Hopefully, someone who has worked thru the Div II interpretations will advise us. I'd like to hear what the conclusions are.