A three-phase, wye-connected, 400-V, four-pole, 60-Hz induction motor has primary leakage impedance of 1 + j2 Ω and secondary leakage impedance referred to the primary at standstill of 1 + j2 Ω. The magnetizing impedance is j40 Ω and the core-loss impedance is 400 Ω. Using the T-equivalent circuit of Figure 13.2.5(a):
(a) Calculate the input current and power (i) on the no-load test (S ≅0) at rated voltage, and (ii) on a blocked-rotor test (S = 1) at rated voltage.
(b) Corresponding to a slip of 0.05, compute the input current, torque, output power, and efficiency.
(c) Determine the starting torque and current; the maximum torque and the corresponding slip; and the maximum output power and the corresponding slip.
For the following parts, use the approximate equivalent circuit obtained by transferring the shunt core loss/magnetizing branch to the input terminals.
(d) Find the same values requested in part (b).
(e) When the machine is driven as an induction generator with a slip of -0.05, calculate the primary current, torque, mechanical power input, and electric power output.
(f) Compute the primary current and the braking torque at the instant of plugging (i.e., reversal of the phase sequence) if the slip immediately before plugging is 0.05.
