Chapter 16, Problem 16.2P

The total flux per pole in the air-gap of a 50-Hz alternator is 0.06 Wb. The flux-density distribution is given by T. The coil-span is 4/5 of a pole pitch. Determine the rms emf per armature turn. Find also the emf per armature turn when the flux were assumed to be sinusoidally distributed.

Label values ​​of a three-phase ASM 50 Hp 60-Hz Y / ∆ 800V / 460V 34A / 59A cos (Q) = 0.85 p = 4 nm = 1425 It is given in rpm. a.) Find the value of the total losses of this asynchronous. b.) What is the speed of the rotary magnetic field if the rotor speed is 950 rpm while the load moment of this asynchronous is 240 Nm? c.) This asynchronous motor rotates at 2350 rpm and its load torque is 180 Nm. Accordingly, rotary magnetic Find the velocity of the field.

An 8 poles, 50HZ, delta connected induction motor having 120 stator slots with 64 conductors in each, and coils shorted by 3 slots. Find the required sinusoidally distributed flux when the motor operates from 380 V supply.

An open-circuit voltage of 480 V appears across the slip-rings of a wound-rotor induction motor when the rotor is locked. The stator has 8 poles and is excited by 60 Hz source. If the rotor is driven by a variable-speed dc motor, calculate the open-circuit voltage and frequency across the slip rings if the dc motor turns a. At 500 r/min, in the same direction as the rotating field b. At 600 r/min, in the same direction as the rotating field c. At 1800 r/min, opposite to the rotating field

2. The star-connected rotor of an induction motor has a standstill impedance of (0.4+j4) ohm per phase and the rheostat impedance per phase is (6+j2) ohm. The motor has an induced e.m.f. of 80 V between slip-rings at standstill when connected to its normal supply voltage. Find (a) rotor current at standstill with the rheostat in the circuit (b) when the slip-rings are short-circuited and the motor is running with a slip of 3%. 3. A4-pole, 50-Hz induction motor has a full-load slip of 5%. Each rotor phase has a resistance of 0.3 Q and a standstill reactance of 1.2 Q. Find the ratio of maximum torque to full-load torque and the speed at which maximum torque occurs. 4. A 3-phase, 4-pole, 50-Hz induction motor has a star-connected rotor. The voltage of each rotor phase at standstill and on open-circuit is 121 V. The rotor resistance per phase is 0.3 and the reactance at standstill is 0.8 N. If the rotor current is 15 A, calculate the speed at which the motor is running. Also, calculate the…

2. The star-connected rotor of an induction motor has a standstill impedance of (0.4 + j4) ohm per phase and the rheostat impedance per phase is (6+j2) ohm. The motor has an induced e.m.f. of 80 V between slip-rings at standstill when connected to its normal supply voltage. Find (a) rotor current at standstill with the rheostat in the circuit (b) when the slip-rings are short-circuited and the motor is running with a slip of 3%. 3. A4-pole, 50-Hz induction motor has a full-load slip of 5%. Each rotor phase has a resistance of 0.3 Q and a standstill reactance of 1.2 Q. Find the ratio of maximum torque to full-load torque and the speed at which maximum torque occurs. [5.27 A ; 3.3 A] [2.6 ; 1125 r.p.m.]

3 For a coil, each turn faces (2t4 – t³ – 2t) milliwebers of flux. The value of induced EMF in coil for 100 turns coil at 2 sec is, (in Volts).

The terminal voltage of a 150 kW series generator is 600 V at rated load. The armature resistance is 0.06 ohms and the series field resistance is 0.04 ohms. Find generated emf.

6) The speed of a d.c. motor can be controlled by varying its flux per pole or resistance of armature circuit. 7) If the impedance triangles of two transformers operating in parallel are not identical in shape and size, the two transformers will run with different power factors. 8) In a DC motor, unidirectional torque is produced with the help of brushes and commutator. 9) The ordinary efficiency of a given transformer is maximum when it runs at half full-load. 10) The series field of a short-shunt d.c. generator is excited by shunt currents. 11) The speed of a d.c. motor can be controlled by varying its flux per pole or resistance of armature circuit. 12) The primary and secondary windings of an ordinary 2-winding transformer always have separate magnetic circuits. 13) A 60 Kw DC four- pole generator has a lap winding if rotated in citrine speed that generate 520 volts, the current flowing in each armature conductors is 22.5A . 14) The function of The Armature is to rectify the…