The induction machine

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EXERCISES FOR ELECTRIC POWER SYSTEMS COURSE ENERGY DEPARTMENT, Electrical section Class 6 The Induction Machine Exercise 1 A three-phase, six-pole, 50 Hz induction motor is supplied by a line-to-line voltage of 380 V. The phases of the rotor/stator are Y-connected and the transformer ratio between the stator and the rotor windings is k = 1.2. In no-load operating conditions, the motor absorbs a current /g1835 /g2868/g34/4 12 /g1827 with a power factor /g1855/g1867/g1871/g2/3//g2868/g34/4 0.13 . In normal operating conditions, the mechanical torque applied to the machine shaft is /g1829/g3/4//g34/4 203 J/rad while the magnitude of the rotor phase current is equal to 40 A and /g1858/g287//g34/4 1.8 /g1834/g1878 . Neglecting the voltage drops in the stator phases, compute for the normal operating conditions: 1. the mechanical power developed by the motor at the shaft; 2. the Joule power losses in the rotor phases; 3. the resistance and inductance of the rotor; 4. the current absorbed by the stator and the corresponding power factor. Exercise 2 A three-phase, eight-pole, 50 Hz induction motor is supplied by a line-to-line voltage of 380 V. In normal operating conditions, the motor absorbs a line current /g1835 /g2869 /g3/39/g34/4 60 /g1827 with a power factor of /g1855/g1867/g1871/g2/3/ /g34/4 0.82 while the fractional slip is /g1871 /g34/4 3.5 %. In no-load operating conditions the motor absorbs a current /g1835/g2868 /g3/39/g34/4 18 /g1827 with a power factor /g1855/g1867/g1871/g2/3//g2868/g34/4 0.12 . The phases of the stator are D-connected and the line-to-line measured resistance is /g1844/g3/4//g34/4 0.162 Ω. For the normal operating conditions compute: 1. the sum of mechanical and iron power losses in the motor; 2. the Joule power losses in the stator and rotor…