convert horsepower to amps
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Re: convert horsepower to amps
Watts divided by volts will divulge amps.
It's all a ratio.
What is the wattage?
What is the voltage?
You'll get your amps.
Now to get started you have to convert horsepower to watts. Here's a nifty chart where you can find the conversion factor:
http://www.mikeholt.com/documents/freestuff/ElectricalFormulas.pdf
That's the nickel tour. There's more to it if your motor has a power factor other than one.
Here is a handy image of Ohm's Law (referenced above):
[ September 17, 2003, 03:22 PM: Message edited by: awwt ]
Watts divided by volts will divulge amps.
It's all a ratio.
What is the wattage?
What is the voltage?
You'll get your amps.
Now to get started you have to convert horsepower to watts. Here's a nifty chart where you can find the conversion factor:
http://www.mikeholt.com/documents/freestuff/ElectricalFormulas.pdf
That's the nickel tour. There's more to it if your motor has a power factor other than one.
Here is a handy image of Ohm's Law (referenced above):
[ September 17, 2003, 03:22 PM: Message edited by: awwt ]
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- Semi-Retired Electrical Engineer
Re: convert horsepower to amps
If you are looking for a simple unit conversion, you can use this:
HP times 746, divided by efficiency, then divided by voltage.
Example, for a 460V, 10 HP motor with an efficiency of 85%:
{ (10 HP) x (746 Watts/HP) } / { .85 efficiency) x (460V) } = 19.08 amps.
If you are looking for a basis for sizing conductors, then look up this same motor in NEC Table 430.150, and you get 14 amps. What?s the difference? I am not certain. The NEC table says that it is based on typical running conditions, and most motors don?t typically run at their full rated horsepower.
[ September 17, 2003, 04:06 PM: Message edited by: charlie b ]
If you are looking for a simple unit conversion, you can use this:
HP times 746, divided by efficiency, then divided by voltage.
Example, for a 460V, 10 HP motor with an efficiency of 85%:
{ (10 HP) x (746 Watts/HP) } / { .85 efficiency) x (460V) } = 19.08 amps.
If you are looking for a basis for sizing conductors, then look up this same motor in NEC Table 430.150, and you get 14 amps. What?s the difference? I am not certain. The NEC table says that it is based on typical running conditions, and most motors don?t typically run at their full rated horsepower.
[ September 17, 2003, 04:06 PM: Message edited by: charlie b ]
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Re: convert horsepower to amps
True, but it does not answer the question. See my previous post on converting HP to amps.
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Re: convert horsepower to amps
Your answer was better. I was trying to be somewhat mysterious so the OP would have to do some thinking
Thanks for your better, more complete, and honest answer. My answer was lacking. I included the PF part but not the EFF part.
../Wayne C.
[ September 17, 2003, 04:30 PM: Message edited by: awwt ]
Your answer was better. I was trying to be somewhat mysterious so the OP would have to do some thinking
Thanks for your better, more complete, and honest answer. My answer was lacking. I included the PF part but not the EFF part.
../Wayne C.
[ September 17, 2003, 04:30 PM: Message edited by: awwt ]
Re: convert horsepower to amps
During the development of engines (back in the old days) there was a move away from using horses to do work. As a system had to be developed to rate the amount of work a engine could produce, "they" chose a logical known quantity. After what I assume a number of trials they arrived at a average amount of work that a horse could produce. The numbers state that 1 horse can lift 550 lbs./1 ft./ in 1 second, or 33000lbs./1 ft./in 1 minute, which is the same amount of applied force as 1 horsepower as we know it. As the steam engine was invented before the electric motor, and being that a watt is a unit of heat, I would assume that a way was found to rate electric motors in the amount of "heat" that they consumed in watts. 746 Watts/HP is the amount it requires in a ideal situation at 100% efficiency. Due to factors such as friction and resistance, 100% efficiency is not possible, hence more power (heat) is required to produce it. In the metric system, force (horsepower in US) is measured in Kilowatts and heat (btu in US) is measured in calories. 1 btu can raise the temperature of 1 pound of pure water /1 degree farenheit. 1 Calorie can raise the temperature of 1 Liter of pure water(1 kilogram)/ 1 degree celsius. As you can see, all of the calculations are made assuming 100% efficiency. In the real world this is not possible so terms such as efficiency and power factor are applied to determine how much heat is required to spin that motor and lift that weight.
During the development of engines (back in the old days) there was a move away from using horses to do work. As a system had to be developed to rate the amount of work a engine could produce, "they" chose a logical known quantity. After what I assume a number of trials they arrived at a average amount of work that a horse could produce. The numbers state that 1 horse can lift 550 lbs./1 ft./ in 1 second, or 33000lbs./1 ft./in 1 minute, which is the same amount of applied force as 1 horsepower as we know it. As the steam engine was invented before the electric motor, and being that a watt is a unit of heat, I would assume that a way was found to rate electric motors in the amount of "heat" that they consumed in watts. 746 Watts/HP is the amount it requires in a ideal situation at 100% efficiency. Due to factors such as friction and resistance, 100% efficiency is not possible, hence more power (heat) is required to produce it. In the metric system, force (horsepower in US) is measured in Kilowatts and heat (btu in US) is measured in calories. 1 btu can raise the temperature of 1 pound of pure water /1 degree farenheit. 1 Calorie can raise the temperature of 1 Liter of pure water(1 kilogram)/ 1 degree celsius. As you can see, all of the calculations are made assuming 100% efficiency. In the real world this is not possible so terms such as efficiency and power factor are applied to determine how much heat is required to spin that motor and lift that weight.
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Re: convert horsepower to amps
Just to keep things complicated.
North American motors are rated in OUTPUT horsepower. To determine their input watts you need to use the formulas Charlie B used. (Charlie you forgot the 1.73 factor for three phase giving an input current of 11.03A versus the overrated NEC value of 14A)
European motors are rated in OUTPUT watts. To determine their input watts you use the same formula except for the 746 conversion factor.
To convert between European motors watts and North American motor horsepower you just need the conversion of 1HP = 746W.
Just to keep things complicated.
North American motors are rated in OUTPUT horsepower. To determine their input watts you need to use the formulas Charlie B used. (Charlie you forgot the 1.73 factor for three phase giving an input current of 11.03A versus the overrated NEC value of 14A)
European motors are rated in OUTPUT watts. To determine their input watts you use the same formula except for the 746 conversion factor.
To convert between European motors watts and North American motor horsepower you just need the conversion of 1HP = 746W.
Re: convert horsepower to amps
Hillbilly,
I think you slipped on the keyboard:
Calories have been out of use for a long time, except for nutritional content. (Is that the right term?) Today, Joule is the commonly used unit for all forms of energy, including heat, as it's much easier to work with: One Watt of power for one second equals one Joule of work.
Hillbilly,
I think you slipped on the keyboard:
Force is measured in Newton while power is measured in watts (or horsepower).
Calories have been out of use for a long time, except for nutritional content. (Is that the right term?) Today, Joule is the commonly used unit for all forms of energy, including heat, as it's much easier to work with: One Watt of power for one second equals one Joule of work.
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Re: convert horsepower to amps
Mea culpa, mea culpa, mea maxima culpa. Thanks for the reminder. It would make sense that the NEC version would be higher (translate ?more conservative?).
If you drink a diet soda that contains one calorie of nutritional content, it will deliver to your system an amount of energy that will produce 1000 calories of heat. Some try to distinguish the two uses of the word ?calorie? by using a capital letter ?C? for the heat version (which, by the way, is also called a ?kilocalorie? ? go figure!) and a small case ?c? for the nutritional version.
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