# Can I calculate the horsepower by only AC current flow in windings in AC motor?

I saw this AC motor parameter calculator online: http://www.engineeringtoolbox.com/electrical-motor-calculator-d_832.html

It says for 100 Horse power, in 90% efficiency, 0.9 Power Factor and 220 V AC supply, 300A current is needed. But when I calculate like:

220V AC * 300 A AC * 0.707 (sine root mean sq) * 0.9 (PF) / 745.7 W (1 Horse power) = 56.3 HP

Where do I confuse about the calculation?

Also, for a special purpose, I need to calculate the horsepower based on current flow in windings. In these windings below:

Because I only know my inductance(L) value, radius(R), turns(N) and RMS current which is going to flow through these winding coils. I know these below;

L = 60 mH

R = 5 cm

d(wire diameter) = 0.4 mm

N = 210

And RMS current for each phase (current flow on armature windings) is 12 A (peak to peak)

how can I calculate the horse power by only these parameters? Can I be sure that this parameters are whether enough or not enough to drive a car? Thanks.

• 220V already is the RMS value. Oct 18 '16 at 14:42
• @JimmyB Oh sorry. I editted the calculation, now its 56 HP. Still not satisfying. Oct 18 '16 at 14:46
• Your link is broken. Oct 18 '16 at 14:48
• And do away with that 1/sqrt(2) factor. Oct 18 '16 at 14:48
• Oh, you're talking about 3 phase. In that case the voltages to use are different. A factor of sqrt(3) may be required. Oct 18 '16 at 14:55

## 1 Answer

Three phase motor:

$$P=\sqrt{3}\cdot U \cdot I\cdot cos\varphi$$

$$P =1.73\cdot 220\cdot300\cdot0.9 \approx 100kW$$