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Negative Phase Sequence

Cameron O'Connell
I have been looking at a calculation formula someone sent to me for the negative phase sequence of an unbalanced three-phase generator. the calculation looks at the three loads applied to L1,L2 & L3. the formula gives the negative phase sequence which should not be more than 20% of the rated maximum current.


I have searched low and high for the source of this information and I can't find it anywhere, would anyone know if it is correct and/or where the information comes from as i have no contact details form the person who originally gave it to me.
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    I have spoken to a few people over the past few days and I have found out a little more info, for an alternator with 12 poles, L1/L2/L3 there would be a 30 degree spacing between each pole, SIN(30) equals 1/2 in part of the equation and COS(30) equals SQRT(3)/2 so each pole is separated by 30 degrees. the unbalanced load gives rise to negative phase current which is an opposing magnetic flux that causes a heating effect that can damage the alternator and it also increases the load current drawn, the 20% can be an additional load to the maximum load on a phase and trip the breaker for overcurrent. I think the value is also divided by 3 for each phase.
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  • 0
    I have spoken to a few people over the past few days and I have found out a little more info, for an alternator with 12 poles, L1/L2/L3 there would be a 30 degree spacing between each pole, SIN(30) equals 1/2 in part of the equation and COS(30) equals SQRT(3)/2 so each pole is separated by 30 degrees. the unbalanced load gives rise to negative phase current which is an opposing magnetic flux that causes a heating effect that can damage the alternator and it also increases the load current drawn, the 20% can be an additional load to the maximum load on a phase and trip the breaker for overcurrent. I think the value is also divided by 3 for each phase.
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