Question

14. The following details are known about a 200 hp, 500 V, 435 rpm de shunt motor: full-load current is 330 A, insulation class is H, weight is 3400 kg, external diameter of the frame is 915 mm and length of the frame is 1260 mm. If the motor is running at full-load, calculate: a. the total losses and efficiency. b, the approximate shunt field exciting current if the shunt field causes 15% of the total losses. the value of the armature resistance as well as the counter-emf, knowing that 45% of the c, total losses at full-load are due to armature resistance. 15. A 3-phase 11 kV 50 Hz squirrel cage induction motor draws a line current of 1.12 kA and a total power of 3.9 MW when operating at full load. The full-load speed is 490 rpm. The stator is wye connected and has an effective resistance per phase of 28.6 m. The stator iron (core) loss is 46 kW; friction and windage losses are 22.7 kW. Calculate at full-load conditions: (a) the power factor; (b) power supplied to the rotor; (c) slip; (d) rotor I'R (copper) losses; (e) developed (mechanical) torque; () efficiency 16. A 1/3-hp, 110 V, 60 Hz, 1140 r/min, split-phase induction motor has the following impedances: The total rotational losses are 291 W. (Note: these losses are charged to the rotor circuit and t for Rm as shown in the textbook. Do not include Rm in the equivalent circuit.) account Calculate: (a) slip; (b) stator current; (c) stator power factor; (d) input power (e) useful rotor power input, () developed (mechanical) power; (g) shaft power; (h) efficiency.

Answer 1

→ 19e shunt motor : full -Load cusexeut 330 A ,v 50o V 149 , 12 kw { so, Qoo hp = 149.12 kw cienC Po 149. IZ kvo pi= Vt = 500 x 330-165 kW M Po 1 Po 141.12 ku 0.037 16s Kw the Apereximate shun fed Exettin B the APPhoxi Cusrent- → the Shunt field ca uses 15% of the total 夂osses. P=((IS.kr kw) /loo) xīs so, → 500 O The value of A - Amature Re sistance 45% 아 the Total losses at Aut 1-Load are olue to asmatuxe Resistance → so, P-is.tr KW x1r 10 o p= 46 W Ra = チ146 the = 0.065 Ω (330)

ウ counte서 - 5000.06s x 330 4734 V Ea So, aumatuxe Resistance s o. o 6S s and counter E