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  1. #1
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    Calculating the motor bhp/hp?

    I have the voltage, FLA, and fan efficiency. I would like to get the bhp. I am assuming this is how the calculation goes, but it doesn't seem to jive so I must be missing something.

    Voltage: 230V
    FLA: 3.2A
    motor efficiency: .65

    Power=Voltage*Current=230*3.2=736 Watts

    motor efficiency = bhp/Power

    0.65=bhp/736 Watts

    bhp = 0.65*736 Watts *1 hp/746 Watts

    bhp = .641287 hp


    Where 1 hp = 746 Watts as the conversion.


    What do you guys think???

  2. #2
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    Looks like about a 1/2 horse to me. I don't know how to figure either, but someone will be along shortly.

  3. #3
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    single phase?
    Hp=( v x a x eff% x power factor) / 746
    Psc motor is 50 - 65% eff.

  4. #4
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    Thread Starter
    I take that back,

    New calculation:

    3 phase power at 230V and 3.2 FLA.
    Power Factor: 0.8

    kVA = 230V*3.2A*sqrt(3)
    kW = kVA*0.8 = 1274*0.8 = 1019.832 W
    bhp = kW/7460 = 1019.832/7460 = 0.136707 hp.

    I'm sort of confident in the above calculation

  5. #5
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    Thread Starter
    Quote Originally Posted by btuhack View Post
    single phase?
    Hp=( v x a x eff% x power factor) / 746
    Psc motor is 50 - 65% eff.
    3 phase so the voltage is 120 degrees out of phase, I get another sqrt(3) factor.

    Let me know what you think of my current calculation

  6. #6
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    Not aware of any 1/8 hp motors @3 ph, plus 3.2 amps is more than 1/8 hp of work.

    (V x A x eff x PF x 1.73)/746

    About .9hp?

    Nema 230/3@1 hp = 3.6 amps. That sounds realistic to me.

  7. #7
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    i would imagine you could find the info you seek here

    www.engineeringtoolbox.com
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  8. #8
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    Thread Starter
    Quote Originally Posted by btuhack View Post
    Not aware of any 1/8 hp motors @3 ph, plus 3.2 amps is more than 1/8 hp of work.

    (V x A x eff x PF x 1.73)/746

    About .9hp?

    Nema 230/3@1 hp = 3.6 amps. That sounds realistic to me.
    230*3.2*.8*.5*1.73/746 = 0.682724. Not exactly sure what this is suppose to calculate?

    Power = V x A x 1.73 = 230*3.2*1.73 = 1273.28 Watts

    KVA·PF = P/1000 x 0.80

    KVA = 1.018624 kW

    1hp = 746 W

    So its about 1.367 hp...

    Anyone?

  9. #9
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    Thread Starter
    Quote Originally Posted by dandyme View Post
    i would imagine you could find the info you seek here

    www.engineeringtoolbox.com
    thats where I'm looking atm.

  10. #10
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    Thread Starter
    bump anyone??

  11. #11
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    Hi OVOleg,
    I agree with btuhack, His formula is the one I use.

    Allen
    UA Local 602
    A man who says that he can't learn anything in a class is exactly right.

  12. #12
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    Quote Originally Posted by Allen View Post
    Hi OVOleg,
    I agree with btuhack, His formula is the one I use.

    Allen
    I'm not disagreeing either I'm just trying to line up the numbers. With his formula I am getting about 0.68 hp and he says its 0.9. What efficiency are you guys considering for these motors?

  13. #13
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    Use .8 default for 3 ph PF and eff unless you know otherwise, so ive been told.

    230 x 3.2 x .8 x .8 x 1.73/746=1.092358HP

    Thats the basic formula that i use.

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