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B. In a series of tests to determine the parameters of an eight pole, three-phase 3300 V, 50 Hz, 500 kW induction motor, the test results were obtained. The stator winding resistance was separately determined to be equal to 0.3 2, and the mechanical losses are equal to 10 kW. Table 1 Test results for wound-rotor induction machine Test Voltage Current Power No-load test 3300 V 4.711 A 10.01 KW Locked-rotor test 336.6 V 86.56 A 12.24 kW (i) Calculate the synchronous speed of the motor. (ii) If the slip at rated load is 0.02, calculate the full-load speed of the motor. Calculate the shaft torque at rated load. (iii) (iv) Using the test results in table 1, calculate the parameters of the approximate equivalent circuit. (v) If the motor is started direct-on-line, calculate the starting current, and the developed starting torque. The magnetizing branch can be neglected in this analysis. (vi) (vii) What is the disadvantage of starting big motors using direct-on-line starting? Calculate the external resistors that should be connected in the rotor circuit to achieve maximum starting torque. (viii) Calculate the starting current and the starting torque when the resistors calculated in part (vii) are in the rotor circuit. (ix) By what factor does the addition of the external resistors increase the starting torque?

B. In a series of tests to determine the parameters of an eight pole, three-phase 3300 V, 50 Hz, 500 kW induction motor, the test results were obtained. The stator winding resistance was separately determined to be equal to 0.3 2, and the mechanical losses are equal to 10 kW. Table 1 Test results for wound-rotor induction machine Test Voltage Current Power No-load test 3300 V 4.711 A 10.01 KW Locked-rotor test 336.6 V 86.56 A 12.24 kW (i) Calculate the synchronous speed of the motor. (ii) If the slip at rated load is 0.02, calculate the full-load speed of the motor. Calculate the shaft torque at rated load. (iii) (iv) Using the test results in table 1, calculate the parameters of the approximate equivalent circuit. (v) If the motor is started direct-on-line, calculate the starting current, and the developed starting torque. The magnetizing branch can be neglected in this analysis. (vi) (vii) What is the disadvantage of starting big motors using direct-on-line starting? Calculate the external resistors that should be connected in the rotor circuit to achieve maximum starting torque. (viii) Calculate the starting current and the starting torque when the resistors calculated in part (vii) are in the rotor circuit. (ix) By what factor does the addition of the external resistors increase the starting torque?

Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
13th Edition
ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
Chapter1: Introduction
Section: Chapter Questions
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B. In a series of tests to determine the parameters of an eight pole, three-phase 3300 V, 50 Hz, 500 kW induction motor, the test results were obtained. The stator winding resistance was separately determined to be equal to 0.3 2, and the mechanical losses are equal to 10 kW. Table 1 Test results for wound-rotor induction machine Test Voltage Current Power No-load test 3300 V 4.711 A 10.01 kW Locked-rotor test 336.6 V 86.56 A 12.24 kW (i) Calculate the synchronous speed of the motor. (ii) If the slip at rated load is 0.02, calculate the full-load speed of the motor. Calculate the shaft torque at rated load. (iii) (iv) Using the test results in table 1, calculate the parameters of the approximate equivalent circuit. (v) If the motor is started direct-on-line, calculate the starting current, and the developed starting torque. The magnetizing branch can be neglected in this analysis. (vi) (vii) What is the disadvantage of starting big motors using direct-on-line starting? Calculate the external resistors that should be connected in the rotor circuit to achieve maximum starting torque. (viii) Calculate the starting current and the starting torque when the resistors calculated in part (vii) are in the rotor circuit. (ix) By what factor does the addition of the external resistors increase the starting torque?
Transcribed Image Text:B. In a series of tests to determine the parameters of an eight pole, three-phase 3300 V, 50 Hz, 500 kW induction motor, the test results were obtained. The stator winding resistance was separately determined to be equal to 0.3 2, and the mechanical losses are equal to 10 kW. Table 1 Test results for wound-rotor induction machine Test Voltage Current Power No-load test 3300 V 4.711 A 10.01 kW Locked-rotor test 336.6 V 86.56 A 12.24 kW (i) Calculate the synchronous speed of the motor. (ii) If the slip at rated load is 0.02, calculate the full-load speed of the motor. Calculate the shaft torque at rated load. (iii) (iv) Using the test results in table 1, calculate the parameters of the approximate equivalent circuit. (v) If the motor is started direct-on-line, calculate the starting current, and the developed starting torque. The magnetizing branch can be neglected in this analysis. (vi) (vii) What is the disadvantage of starting big motors using direct-on-line starting? Calculate the external resistors that should be connected in the rotor circuit to achieve maximum starting torque. (viii) Calculate the starting current and the starting torque when the resistors calculated in part (vii) are in the rotor circuit. (ix) By what factor does the addition of the external resistors increase the starting torque?
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