Problem 1 20 Pts Induction Motors 1 The S Is The Slip And Ns Is The Synchronous Speed Then The Actual Running Speed 1 (29.16 KiB) Viewed 39 times
Problem 1 20 Pts Induction Motors 1 The S Is The Slip And Ns Is The Synchronous Speed Then The Actual Running Speed 2 (29.83 KiB) Viewed 39 times
Problem 1. (20 pts) Induction Motors 1. The s is the slip and Ns is the synchronous speed, then the actual running speed of the motor will be (a) Ns (b) s. (c) (-s)Ns (d) (Ns-I)s 2. The efficiency of the induction motor is? - a) 60 to 90% -(b) 80 to 90% -(c) 95 to 98% -(d) 99% 3. In the squirrel-cage induction motor, the number of slip rings is usually? (a) two -(b) three (c) four (d) none 4. In a squirrel-cage induction motor, the starting torque is usually? -(a) low (b) negligible - (c) same as full-load torque (d) slightly more than full-load torque 5. The Star-delta starting of motors is not usually applicable in case of? -(a) single-phase motors (b) variable speed motors (c) low horsepower motors (d) high-speed motors 6. An induction motor is also called as? (a) D.C. compound motor -(b) D.C. series motor (c) synchronous motor (d) asynchronous motor 7. In the induction motor, the good power factor can be achieved if the average flux density in the air gap is? .(a) absent .(b) small (c) large .(d) infinity
equency equency of the three-phase induction motor is 50 Hz and slip is of 4%? (a) 200 Hz (b) 50 Hz (c)2 Hz (d) 0.2 Hz 9. What happens when Induction motor runs at synchronous speed, motor will answer choices • Burn • Stop • Delivers Real Power • Delivers reactive power 10. Starting Currents of 3-Phase Induction Motor is about times of the full load current: answer choices Half 2 to 3 5 to 7 10 to 20 Problem 2. (20 pts) Induction Motors. What is the purpose of the auxiliary wind- ing in a single-phase induction motor? How can we change the rotation of such a motor? b A6-pole, singlo-phase motor is connected to a 60 Hz source. What is its synchronous speed? с Name a motor from for each of the following devices (Chapter 18): a. A small portable drill b. A 3/4 hp air compressor c. A vacuum cleaner d. A 1/100 hp blower e. A 1/3 hp centrifugal pump d State the main difference between a split- phase motor and a capacitor-start motor What are their relative advantages? Answers
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