ALERT: VFD Motors Used in Classified Areas
ALERT: VFD Motors Used in Classified Areas
(OP)
I just learned of a safety issue that may exist with medium voltage VFD driven motors used in Class 1, Division 2 classified areas.
In some configurations, the stored electrical potential energy between the motor shaft and grounded surfaces may exceed the minimum ignition energy for the location in which they are operating.
If your VFD motor installation is in a classified area, I suggest you contact your vendor.
So far, I haven't learned of any incident or event leading to this alert!
In some configurations, the stored electrical potential energy between the motor shaft and grounded surfaces may exceed the minimum ignition energy for the location in which they are operating.
If your VFD motor installation is in a classified area, I suggest you contact your vendor.
So far, I haven't learned of any incident or event leading to this alert!





RE: ALERT: VFD Motors Used in Classified Areas
Sorry for all the questions, but every once in a while, the explosion proof dragon raises its head on something I am involved with.
RE: ALERT: VFD Motors Used in Classified Areas
RE: ALERT: VFD Motors Used in Classified Areas
No mention of LV... just MV!
Strongly suggest web search for Product Safety Alert.
RE: ALERT: VFD Motors Used in Classified Areas
Where ignitable concentrations of flammable gases, vapours or liquids are not likely to exist under normal operating conditions.
Note: Only hazardous under ABNORMAL conditions.
---------------------------------------------------------
Occurance of all items taking place at exactly the same time, with the correct percetanges of air/vapour, ignition point, amount of stored energy being discharged....and other relevant factors, highly unlikely.
-----------------------------------------------------------
Some LV, all MV and HV motor shafts must be grounded on VFD applications. Common current configuration should be that MV and HV motors include both insulated bearing - NDE, and shaft ground brush on DE. Always ensure that shaft voltage are discharged.
-----------------------------------------------------------
Are the motor(s) certified as Div 2, Class I. and can the manufacturer issue a Certification of Compliance.
-----------------------------------------------------------
Space Heaters in Div 2, Class I motors can be ignition source. (They could be on for long periods).
RE: ALERT: VFD Motors Used in Classified Areas
http://www.buhlergroup.com/gd/en/masch_kugel.asp
for ATEX and drive of explosion proof design
RE: ALERT: VFD Motors Used in Classified Areas
http://www.mining-technology.com/contractors/controls/saminco/
for the explosion-proof display
RE: ALERT: VFD Motors Used in Classified Areas
My alert applied to existing motors, previously approved for Class I, Div 2 classified areas, but had not been specifically approved for use with VFD drives.
Mishlove,
While your statement regarding probability is technically correct, i.e. highly unlikely, the value of 1 hour in 10,000 hours is the usual prescribed limit.
Space heaters are considered as being equal to the main windings, i.e., not normally sparking! But, if shaft arcing is likely to occur, then, that arcing presence will likely exceed the 1 in 10,000 hour duration.
My alert was intended for users of Medium-Voltage VFD installations to check with their vendor.
RE: ALERT: VFD Motors Used in Classified Areas
Thanks for the clarification. Out of interest....Does this value relate to Divisions or Zones ? EU (ATEX) or North American.
I'm not clear on yr Space Heater comment. Our primary concern would be for surface temp and type of heater.
I believe yr alert to be well received, especially with respect to retrofits. I have not found any guidelines governing this area, by any Standards Organizations, and beleive that caution should be the order of the day.
Cheers
RE: ALERT: VFD Motors Used in Classified Areas
The alert was for USA Class I, Div 2, classified areas.