Question 262Electricity/Electronics - Assistant Engineer70% to pass
The torque-speed and current-speed curves for a three-phase induction motor with a squirrel cage rotor are shown in figures "A" and "B" of the illustration. Which of the following statements is true concerning the depicted curves? Illustration EL-0056
AI Explanation
The correct answer is C) Starting current is approximately 4.75 times the normal full load current value.
This is correct because for a three-phase induction motor with a squirrel cage rotor, the starting current is typically 4 to 6 times the normal full load current value. This high starting current is due to the low resistance of the rotor winding when the motor is starting and the motor is drawing a large amount of current to overcome the initial torque required to start the load.
The other options are incorrect because: A) Rated torque and current typically occur at around 80-85% slip, not 20%. B) The starting current is usually higher than 1.5 times the full load current. D) The pull-up torque is typically around 150-200% of the full load torque, not 20%.
Related Questions
#260 In a three-phase, squirrel-cage type, induction motor, how is the primary rotating magnetic field established? #261 Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? #263 Assuming that the 3-phase power source has a phase sequence of A-B-C and that the motor is connected as shown in figure "A", if the motor has a clockwise (CW) rotation, what statement is true concerning the motors connected as shown in the other figures? Illustration EL-0156 #264 According to 46 CFR, Subchapter J (Electrical Engineering), in response to a loss of normal power or a simulated test, when will the emergency loads automatically be transferred to the emergency diesel-generator? #265 Emergency generators are required to automatically start upon a loss of normal supply voltage, according to 46 CFR, Subchapter J (Electrical Engineering). In conducting a test of the emergency generator automatic transfer of load function, if the normal system supply voltage is 450 VAC, to what value would the emergency generator output voltage have to rise to trigger the automatic transfer of emergency loads to the emergency generator?