A 3-phase, 200-hp, 3300-V, star-connected induction motor has the following equivalent circuit parameters per phase: R1 = R2 =0.8 ohm; x1 x'2 3.5 ohm Calculate the slip at full load if the friction and windage loss is 3 kW. How much extra rotor resistance would be necessary to increase the slip to three times this value with the full-load torque maintained? How much extra stator resistance would be necessary to achieve the same object and what loss of peak torque would result?

A 3-0, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill between slip-rings on open circuit. Calculate the current and power factor in each phase of the rotor windings at standstill when joined to a star-connected circuit, each limb of which has a resistance of 10 Q and an inductance of 0.03 H. The resistance per phase of the rotor windings is 0.2 Q and inductance 0.03 H. Calculate also the current and power factor in each rotor phase when the rings are short- circuited and the motor is running with a slip of 4 per cent. [13.6 A, 0.48; 27.0 A, 0.47] (London University) A 4-pole, 50-Hz, 3-phase induction motor has a slip-ring rotor with a resistance and standstill reactance of 0.04 2 and 0.2 2 per phase respectively. Find the amount of resistance to be inserted in each rotor phase to obtain full-load torque at starting. What will be the approximate power factor in the rotor at this instant ? The slip at full-load is 3 per cent. [0.084 2, 0.516 p.f.]…

A 3-phase, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill between the slip-rings on open-circuit. Calculate the current and power factor at standstill when the rotor winding is joined to a star-connected external circuit, each phase of which has a resistance of 10 Q and an inductance of 0.04 H. The resistance per phase of the rotor winding is 0.2 N and its inductance is 0.04 H. 4. Also, calculate the current and power factor when the slip-rings are short-circuited and the motor is running with a slip of 5 per cent. Assume the flux to remain constant. Identify it`s given and solve it

A value of magnetizing current in a 3-phase induction motor * gives power factor smaller .. larger smaller. .poor large . better O large...poor O

L-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) no

3. A 440V 60-hp six pole 60 hz A connected induction motor has the following parameters R1=0.048 R2= 0.035 Xm= 9.50 X1= 0.33 0 X2= 0.37 0 Pcore= 600W PF&W= 350W Use the Thevenin's Equivalent circuit concept to find: (a)Vth and Zth seen by the rotor circuit (b)The slip at which maximum torque occurs (c) the value of Max/pullout Torques (d) The starting torque.

A three –phase, 440V, 50 Hz, 6 – pole induction motor running at 950 rpm takes 50 kW at certain load. The friction and windage loss is 1.5 kW and the stator losses = 1.2 kW. Determine the output from the rotor. (a). 42.68 kW                 (b). 46.48 kW (c). 48.80 kW                 (d). 44. 86 kW

An induction motor having full load torque of 60 Nm when delta-connected develops a starting torque of 120 Nm. For the same supply voltage, if motor is changed to star -connection, then starting torque developed will be Nm.

Q4/B/ What are the principal characteristics of a series DC motor? What are its uses? Core Mc

A 4 Pole, 50 Three Phase Motor 25 Kg. The meter produces a maximum torque of 1350 Nm per minute. So calculate the torque developed with 5 percent slip. The rotor resistance per winding is 0.5 ohm.