We have in our NGL Plant, 3 explosi
We have in our NGL Plant, 3 explosi
(OP)
We have in our NGL Plant, 3 explosion - proof small motors rated 1.5 HP,230 VAC, 3 Phase.Those motors have experienced repeative failures which led to 2 motors burnt out to-date.
Further, our investigation revealed that the motor failure occurred during mechanical seizure in the pump unit, which caused a locked-rotor condition. It failed due to exposure to a prolonged or sustained overload, since the the control circuit is only protected by a 15 Ampere Circuit Breaker, with no additional motor protection.The high load current experienced at this condition, possibly reaching as high as 34 Amperes based on the motor design, which caused deterioration of the winding insulation and eventual motor burnt out because of overheating.
Is it possible to review the existing control circuit and provide an additional motor protection against prolonged overload condition?
Further, our investigation revealed that the motor failure occurred during mechanical seizure in the pump unit, which caused a locked-rotor condition. It failed due to exposure to a prolonged or sustained overload, since the the control circuit is only protected by a 15 Ampere Circuit Breaker, with no additional motor protection.The high load current experienced at this condition, possibly reaching as high as 34 Amperes based on the motor design, which caused deterioration of the winding insulation and eventual motor burnt out because of overheating.
Is it possible to review the existing control circuit and provide an additional motor protection against prolonged overload condition?





RE: We have in our NGL Plant, 3 explosi
For a small motor such as yours, I don't think the same economic considerations apply, but I would think that code (fire safety) requirements would dictate protection which is sensitive to trip off the motor before potentially damaging currents occur. I'm sure there are others on this board that can provide more insight.
RE: We have in our NGL Plant, 3 explosi
Is there a motor starter in the circuit? If yes, then contact the manufacturer for details of available thermnal overload. If no, then consider adding a contactor + thermal overload for this purposes.
I just found this site www.pbeng.co.uk (good to see that they are still around) on one of the other forums, visit it & look at the Microvision relay, which has integral CTs for protection of motors with FLA 1-15A. Might be an idea for a retrofit - note that it includes protection against running stall (trips if motor current increases dramatically after a period of running at or below FLA, sounds like your case).
RE: We have in our NGL Plant, 3 explosi
RE: We have in our NGL Plant, 3 explosi
peterb is correct in his assessment of this problem.
RE: We have in our NGL Plant, 3 explosi
RE: We have in our NGL Plant, 3 explosi
jbartos,
A circuit breaker alone cannot provide adequate protection for a motor. If you look at the trip curves of a circuit breaker Vs an overload, you will see that they are completely different.
RE: We have in our NGL Plant, 3 explosi
I've only seen motor circuit protectors (MCPs like Cutler-Hammer HMCP, Square D Mag-Gard, etc.) with adjustable magnetic trip only.
RE: We have in our NGL Plant, 3 explosi
I'm sure that there are quite a few manufacturers (I only know of two):
Allen Bradley Bulletin 140
Schneider (Telemecanique) GVN
RE: We have in our NGL Plant, 3 explosi
kind regds.
RE: We have in our NGL Plant, 3 explosi
RE: We have in our NGL Plant, 3 explosi
http://www.geindustrial.com/products/applications/DET-118A.pdf
for GE MicroVersa Trip
http://gess.ge.com/pdf/gea-400low.pdf
etc.
Generally, if the protective device I-t curve is below the thermal overload relay curve, then the motor is consider more sensitively protected.
RE: We have in our NGL Plant, 3 explosi
RE: We have in our NGL Plant, 3 explosi
http://www.pge.com/002_biz_svc/002c1c_understanding.shtml
(Under "Single Phase Protection")
http://www.prodigit.com/e2000c.htm
etc. for more info.