Dunki's sqrt(3)*rated voltage motor life rule of thumb
Dunki's sqrt(3)*rated voltage motor life rule of thumb
(OP)
Greetings:
Can anyone familiar with the following rule of thumb,
"one hour of operation at sqrt(3) times rated voltage equates to about 700 h of operation at unity (rated) voltage" from "The Reality of High Resistance Grounding", Dunki-Jacobs, IEEE Trans. On Industrial Applications, Vol. IA-13, No. 5,1977
please offer some thoughts as to how this rule is figured? Thanks for your help.
Can anyone familiar with the following rule of thumb,
"one hour of operation at sqrt(3) times rated voltage equates to about 700 h of operation at unity (rated) voltage" from "The Reality of High Resistance Grounding", Dunki-Jacobs, IEEE Trans. On Industrial Applications, Vol. IA-13, No. 5,1977
please offer some thoughts as to how this rule is figured? Thanks for your help.






RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
Your question may be valid but please include enough context to identify the specific application.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
I don't follow your math.. I would say the operation at the voltage stated would reduce the life time hours = 700/expected lifetime hrs.
I am not familiar with this rule. Reduction seems high.
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
Did I slip a decimal place? Sorry. Still an unrealistic figure for most motors.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
"It may be of interest to speculate on the probablity that (life) x V12 is a constant, which relates to the expectation that one hour of operation at (sqrt 3) times rated voltage equates to about 700 h of operation at unity (rated) voltage. This estimation becomes, however, invalid for low voltage."
Dunki-Jacobs was speculating on motor life being roughly proportional to the 12th power of voltage. Sqrt312 = 729.
He did say it doesn't apply at low voltages. That portion of the article was discussing medium voltage systems and motors.
It would be interesting to know the background on the 12th power theory.
I checked the references but there were only articles by Fran Fox, Clyde Tipton & others discussing practical experience with HRG on the old 2400V delta systems at the Chevron refinery. (I started my career working for Clyde and installed some of Fran Fox's systems there.)
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
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(2B)+(2B)' ?
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb
2.6 H. S. Endicott, B. D. Hatch, and R. G. Sohmen, “Application of the Erying Model to Capacitor
Aging Data,” IEEE Trans. CP-12, March 1965, 34–40.
2.7 A. W. W. Cameron and M. Kurtz, “A Utility’s Functional Evaluation Tests for High Voltage Stator
Insulation,” AIEE Trans. Vol. 78, Part III, June 1959, 174–184.
2.8 Wichmann, “Accelerated Voltage Endurance Testing of Micaceous Insulation Systems for Large
Turbogenerators Under Combined Stresses,” IEEE Trans. PAS, Jan. 1977, 255–260.
2.9 D. R. Johnston et al., “Frequency Acceleration of Voltage Endurance,” IEEE Trans. EI, June
1979, 121–126.
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(2B)+(2B)' ?
RE: Dunki's sqrt(3)*rated voltage motor life rule of thumb