Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
(OP)
I have an application for a 6P-250HP, Class 1, Zone 2 / Div. 2, VFD duty motor, PD Pump, CT application, V-Belt with an insulation NDE bearing on jack pump (oil) application.
My pump OEM has advise me that his motor supplier has declined to quote, because it's their policy not quote motors in Zone 2/ Div 2 areas with insulated NDE bearing. It was explained to me it's bacause of possible shaft voltage issues that might cause / create a spark.
Has anyone heard of this possible issue.
thanks
Macmckim
My pump OEM has advise me that his motor supplier has declined to quote, because it's their policy not quote motors in Zone 2/ Div 2 areas with insulated NDE bearing. It was explained to me it's bacause of possible shaft voltage issues that might cause / create a spark.
Has anyone heard of this possible issue.
thanks
Macmckim





RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
"Will work for salami"
RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
Best to you,
Goober Dave
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RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
Not static voltage, but shaft current/voltages from the rotor when using on a VFD. I have look high and low in books
and internet and yet to find anything on the subject in a Zone 2 area.
macmckim
RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
The key is: does the electrical device (motor in your case) create arc, spark, or surface temperature near or above the autoignition temperature of the flammable gas in question. If not, an enclosure for ordinary locations is fine. If so, it needs to be listed and labeled for Div 1 locations. If unsure, I think the proper choice will be the safe option. If the motor manufacturer is scared of it, I would take that as a strong hint.
Best to you,
Goober Dave
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RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
More typical voltages are between 10 and 20 V. Sometimes more. And the possible current from shaft to ground (when short-circuiting shaft to ground with a braid) is sometimes up to 10 A RMS. Siemens and ABB usually want to limit the current to under 1 A, but that is often not possible.
The available energy is enough to light any flammable gas* and I have never been involved in PWM fed motors in Ex zones. I guess because they are very rare. For a reason.
*It can also light an incandescent bulb in some cases.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
"Will work for salami"
RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
I believe there's a requirement for the motor and VFD to be a tested and rated combination for use in Hazardous locations. This is based on the fact that a rated motor is rated assuming sinusoidal voltage is applied and that the VFD output waveform will cause more motor heating.
RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Zone 2 / Div 2, VFD Duty Motor with Insulated NDE Bearing
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies