small motor service factor

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Part 77

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Attempting to set Allen Bradley OL solid state relays for Auma MOV 3 phase 480V 1.5KW motors FLA=4. Motor is marked "Duty-15" which I assume means 15 minute intermittent duty. With no SF rating on the nameplate, one must assume SF=1 since anything above is required on the nameplate. AB directs OL setting of a SF=1 motor to .9 of nameplate FLA. (4x.9=3.6 amps)Should I derate the .9 setting even more for this 15 minute duty motor? TIA
 
Part 77 said:
Attempting to set Allen Bradley OL solid state relays for Auma MOV 3 phase 480V 1.5KW motors FLA=4. Motor is marked "Duty-15" which I assume means 15 minute intermittent duty. With no SF rating on the nameplate, one must assume SF=1 since anything above is required on the nameplate. AB directs OL setting of a SF=1 motor to .9 of nameplate FLA. (4x.9=3.6 amps)Should I derate the .9 setting even more for this 15 minute duty motor? TIA
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Just thinking....I guess the only reason the motor would run longer than 15 minutes is, if the MOV didnt make the end travel limit and set there in LRA, or if you cycled the thing too often? Hmm...closer protection on the motor may not be as important as getting a good seat on the valve on closure. I would measure the FLA when it comes up on seat and make up my mind from there.....my two cents...good protection is great, but also is reliability of the MOV operation
 
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