# Thread: Calculating the motor bhp/hp?

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

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

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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

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Originally Posted by btuhack
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

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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

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

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i would imagine you could find the info you seek here

www.engineeringtoolbox.com

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Originally Posted by btuhack
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

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

Anyone?

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Originally Posted by dandyme
i would imagine you could find the info you seek here

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

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bump anyone??

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

Allen

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Originally Posted by Allen
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?

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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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