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Loads - Note 1

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MOTOR EFFICIENCY DISSECTED


ANALYSIS

1.) Law of Conservation of Energy (ideal):

W,in = W,out

2.) First Law of Thermodynamics (practical):

Q = W + dU
Total energy = Work done + change in Internal energy
W,in = W,out + W,losses

W,in > W,out

Energy input is always greater than energy output because of energy losses.

3.) Utilizing energy through time:

(W,in / t) = (W,out / t) + (W,losses / t)

4.) Power and energy relationship:

P = W / t

P,in = W,in / t
P,out = W,out / t
P,losses = W,losses / t

5.) Power flow equation:

P,in = P,out + P,losses

P,in > P,out

Power input is always greater than power output because of power losses.

6.) Usable power and energy:

efficiency = (P,out / P,in) * 100
efficiency = (W,out / W,in) * 100

SUMMARY

Motor efficiency is all about how well a motor converts energy input into energy output, given imperfections like friction and waste heat.

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