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ee362 hw4 - 3 EE 362 HOMEWORK4 DUE:Agril 3Oz 2010z 17:00 A...

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Unformatted text preview: ( 3 EE 362 HOMEWORK4 DUE :Agril 3Oz 2010z 17:00 A 3- phase , Y-connected, 230 volts line-to-neutral, 50 Hz, 8pole induction motor drives a constant-torque load of 1340 Nm at a slip of 5% while delivering full-load power to the load. Neglect friction and windage losses. Induction m/c parameters: r1: 0.097 9 ' r; = 0,06 :2 x3= 0.196 n x2’= 0.161 n a. Calculate speed and power output for the basic motor. b. Calculate slip and power output for the above load by neglecting erl and x2! in comparison with ( r2 / s) in the general torque expression. Compare the results in (b) with those of (a). ’ c. Find the new shaft speed by assuming that frequency of applied stator voltages is reduced to 25 Hz and (V1 / f) ratio is kept constant. Calculate also power output and slip. d. Repeat (c) by using the straight line approximation defined in part (b). Compare and comment on the results of (c) and (d). e. If now the frequency is suddenly reduced to 45 Hz while the system is operating as in part (a) in the steady-state (V1 / f) ratio is kept constant, what will happen to the operation mode of the system and that of the induction m/c. Compute slip, speed, electromechanical torque and gross mech output power just after frequency reduction. Draw the new rotor power flow diagram. Use the straight line approximation given in (b). Comment on the results. f. If now the phase sequence of applied stator voltages is suddenly reversed while the system is operating as in part (a) in the steady-state, what will happen to the new operation of induction m/c? Draw new rotor power flow diagram. Use the general torque expression. Comment on the results. ...
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