
Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
Speed Control and Starting of D.C. Motors
Typology: Cheat Sheet
1 / 1
This page cannot be seen from the preview
Don't miss anything!
UEE3 01 Direct Current Machines and Transformers TUTORIAL 5: Speed Control and Starting of D.C. Motors Course Instructors: Dr. Prasenjit Basak, Dr. Amit Kumar Q1. A 230 V DC shunt motor has an armature circuit resistance of 0.4 Ω and field resistance of 115 Ω. This motor drives a constant torque load and takes an armature current of 20 A at 800 rpm. If the motor speed is to be raised from 800 to 1000 rpm, find the resistance that must be inserted in the shunt field circuit. Assume magnetization curve to be a straight line. [29.93 Ω] Q2. A DC shunt motor takes 50 A on full load from 250 V mains. Its speed is to be raised by 40% by weakening of the field flux. If the torque at raised speed is 20% more than that at the initial speed, find the percntage change in filed field flux. The armature resistance (including brushes) is 0.5 Ω. [35.3%] Q3. (a) Explain what would happen if the DC motor is directly switched on to the supply without any starter. (b) Explain the functionof no-volt release in a three-point starter. (c) Explain the advantages of four-point starter over the three-point starter. (d) What is the difference between a starter and a controller? (e) What would happen if the external resistance for starting of the DC motor is left in the armature circuit?