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1hp equals 746 watts?

Discussion in 'General Electronics Chat' started by Njguy, Jan 27, 2010.

  1. Njguy

    Njguy Member

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    I was just curious how they came up with that number. That 746 watts equals 1hp in an electric motor. I am assuming that 1hp is the mechanical power of 550 foot-pounds per second. With friction and electrical inefficiencies 1hp motors usually sells for 1000 watts plus. Are you telling me that they have not been able to come up with an electric motor that can generate 1hp for less wattage than 746?
     
    Last edited: Jan 27, 2010
  2. JimB

    JimB Super Moderator Most Helpful Member

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    1HP = 746Watts is a fundamental bit of physics.

    Horse Power and Watts are just two different units for the physical quantity "Power", in the same way as Pounds per Square Inch (PSI) and Bar are different units for the physical quantity "Pressure".

    1hp = 746watts no matter how efficient the motor or how much friction in the bearings.

    1bar = 14.5psi no matter how efficient the pump or whether it is pumping water or treacle.

    JimB
     
  3. Diver300

    Diver300 Well-Known Member

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    Horsepower - Wikipedia, the free encyclopedia

    hp and Watts are both units of power. Power can be electric or mechanical, and can be converted between the two. Any conversion will be less than 100 % efficient.

    It is only for historic reasons that electrical power is measured in Watts not hp, like the way that tyre widths are in mm but rim diameter are in inches.

    One pound is 4.44822 Newtons
    One foot is 0.3048 metres

    so 550 foot pounds per seconds, converted to metric, is 550 x 0.3048 x 4.44822 Newton meters per second, which is 745.7 Newton meters per second, better known as Watts.

    A 1 hp motor cannot use less than 745.7 W, so if it uses 1 kW it is about 75% efficient, which sounds about right for a motor of that size.
     
  4. Ubergeek63

    Ubergeek63 Well-Known Member

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    not really...that would be the PEAK efficiency that the motor can only manage over about 20% of it's operating range. The operating range of a typical motor averages 60% efficiency...

    Electric motor basics

    unless of course it is a drastically different motor structure as in those from Novatorque that gets 90% over 80% of it's operating range:

    NovaTorque PurePower-150 Motor

    If you project these efficiencies into electric vehicles you find that it would be quite easy to DOUBLE the range for no extra money! The catch is the lack of current motor designs in that category... it would suit me, were I to win the lottery, to pay for them to design a small vehicle motor and buy 1000 of them and put out AFFORDABLE PEV kits. That would force the ignorant jerk car makers to get off their immensely bulbous backsides.

    Dan
     
    Last edited: Jan 27, 2010
  5. mneary

    mneary New Member

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    Does the Prius, et al, not use the advanced AC permanent magnet design, or is unique to the small NovaTorque offerings?
     
  6. Ubergeek63

    Ubergeek63 Well-Known Member

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    the car companies all use proprietary crap as far as i know. they fear the thought of using anything that someone else could go out and buy. that does not preclude their using novatorque, accept for the fact that novatorque has only been in existence since 2005.

    i am sure they are using "standard" premium efficient motors with tweaks and NDAs, but they are to bloody cheap to get anything like the full custom solar racer motors and to ignorant to use NovaTorque. Remember big business thinks that secrecy protects their investment instead of realizing that openness prevents them from having to make the investment in the first place. They peddle substandard crap at high markups relying on NDAs and trade secrets to prevent the public from realizing it and the competition from topping it.

    I am quite sure they are semi custom designs but use the same techniques used for decades in motors with a twist of rare earth as opposed to the intelligent novatorque style design.

    Dan
     
  7. mneary

    mneary New Member

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    Oh. I guess I missed the part where NovaTorque would help anyone to reproduce and upscale their design, without remuneration.

    Matter of fact, I still can't find it.
     
  8. Boncuk

    Boncuk New Member

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    1HP is not equal to 1HP.

    US car manufacturers use SAE-HP, measured at the crankshaft of the engine. European car manufacturers measure DIN-HP, measured at the drive shaft, thus subtracting the power the engine requires to keep rotating.

    1 SEA-HP equals 746W, 1 DIN-HP equals 736W.

    One DIN-HP is defined moving 75kg up and forward 1m within 1 second.
     
    Last edited: Jan 27, 2010
  9. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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