hde_electric
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How important is it to know the power factor and efficency of a motor and how do I apply it?
How Important is It knowing the Power Factor and Efficie
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Re: How Important is It knowing the Power Factor and Efficie
If you are talking about a 1/2 or 1 HP motor they are not that important. If you are talking about a 1000 HP motor then the power factor and efficiency is important in sizing the generator or other supply that will be used to power the load.
If you are talking about a 1/2 or 1 HP motor they are not that important. If you are talking about a 1000 HP motor then the power factor and efficiency is important in sizing the generator or other supply that will be used to power the load.
tony_psuee
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Re: How Important is It knowing the Power Factor and Efficie
Power factor and efficiency are not an issue in sizing wire, starters, OCP etc. If you or your customer are concerned about kwh cost from the utility on larger motors, or as mclain states, then you will want to look at power factor correction of you motor loads.
Tony
Power factor and efficiency are not an issue in sizing wire, starters, OCP etc. If you or your customer are concerned about kwh cost from the utility on larger motors, or as mclain states, then you will want to look at power factor correction of you motor loads.
Tony
Re: How Important is It knowing the Power Factor and Efficie
mclain:
I would have to argue that since smaller motors single phase motors have lower power factors and lower effiencies than larger motors, these may be more important for smaller motors.
Of course, it would depend on exactly what you're calculation. If you have one hundred 1 horsepower motors on a generator, PF & eff. are very important for the calculation.
If you have one 1 hp motor, and one 100 hp motor on the same generator, of course you would be right. The 100 hp motor would swamp the calculations.
mclain:
I would have to argue that since smaller motors single phase motors have lower power factors and lower effiencies than larger motors, these may be more important for smaller motors.
Of course, it would depend on exactly what you're calculation. If you have one hundred 1 horsepower motors on a generator, PF & eff. are very important for the calculation.
If you have one 1 hp motor, and one 100 hp motor on the same generator, of course you would be right. The 100 hp motor would swamp the calculations.
Ed MacLaren
Senior Member
Re: How Important is It knowing the Power Factor and Efficie
If you don't need exact values, there is a "rule of thumb" for three phase, general purpose, normal speed, integral-horspower motors.
It takes approximately 1 Kva (1000 va) input, to get 1 HP (746 watts) output.
For fractional-horsepower three phase motors, approximately 1.5 Kva (1500 va) input, to get 1 HP output.
For fractional-horsepower single phase motors, approximately 2 Kva (2000 va) input, for each horspower of output.
Ed
[ September 16, 2003, 08:53 PM: Message edited by: Ed MacLaren ]
If you don't need exact values, there is a "rule of thumb" for three phase, general purpose, normal speed, integral-horspower motors.
It takes approximately 1 Kva (1000 va) input, to get 1 HP (746 watts) output.
For fractional-horsepower three phase motors, approximately 1.5 Kva (1500 va) input, to get 1 HP output.
For fractional-horsepower single phase motors, approximately 2 Kva (2000 va) input, for each horspower of output.
Ed
[ September 16, 2003, 08:53 PM: Message edited by: Ed MacLaren ]
frenchelectrican
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Re: How Important is It knowing the Power Factor and Efficie
bonsoir (hello) ed;
i will like to make a adment here for the motor also bear in mind the transformer too i use the same rules apply to the transfomer
merci, marc
bonsoir (hello) ed;
i will like to make a adment here for the motor also bear in mind the transformer too i use the same rules apply to the transfomer
merci, marc
Re: How Important is It knowing the Power Factor and Efficie
steve66
You are right I didn't consider 100 1 HP motors on a circuit. We run 6 1000 HP DC Traction motor powered by a SCR drive. The power factor is around .6 to .7. We have numerous 480 volt 3 ph motors and they have little effect on the power factor incomparison to the DC Traction motors. But your point is well taken.
steve66
You are right I didn't consider 100 1 HP motors on a circuit. We run 6 1000 HP DC Traction motor powered by a SCR drive. The power factor is around .6 to .7. We have numerous 480 volt 3 ph motors and they have little effect on the power factor incomparison to the DC Traction motors. But your point is well taken.
hde_electric
Member
Re: How Important is It knowing the Power Factor and Efficie
I really appreciate all the input thanks and I wll keep everything in mind.
I really appreciate all the input thanks and I wll keep everything in mind.
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