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This is the given equivalent circuit for the above parameters (from the problem's solution):

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The resistance is R2[(1-s)/s].

However, my textbook shows that the resistance is instead R2/s for the equivalent circuit of an induction motor:

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What is the significance in the discrepancy between R2/s and R2[(1-s)/s]?

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2 Answers 2

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In your top circuit, R2 is also shown as a seperate component. In the bottom circuit, R2 is combined such that: -

$$R_2 + R_2\cdot\dfrac{1-s}{s} = \dfrac{R_2}{s}$$

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What is the significance in the discrepancy between R2/s and R2[(1-s)/s]?

R2/s = R2 + R2[(1-s)/s]

The power dissipated in R2/s is the total power developed in the rotor. The power in R2 is dissipated as heat in the rotor. The power in R2[(1-s)/s] is electrical power converted to mechanical power.

Breaking R2/s into two parts more clearly illustrates what happens to the power developed in the rotor.

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  • \$\begingroup\$ I think you need to check your algebra. \$\endgroup\$
    – Andy aka
    Commented Jul 28, 2019 at 15:05
  • \$\begingroup\$ Thank you @Andy aka \$\endgroup\$
    – user80875
    Commented Jul 28, 2019 at 15:12

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