Homework Help is Here – Start Your Trial Now!
Engineering
Electrical Engineering
A separately excited DC motor drives a constant torque mechanical load. The armature resistance is 0.20 and the nominal armature current is la=74A. The nominal rotational speed of the motor is 1150 rpm. The armature winding is supplied from a 220V DC source. Rotational losses can be neglected. a) What is the load torque if the machine draws the nominal armature current while running at the nominal rotational speed? b) Under the same load, the field winding current is decreased by 20%. Calculate the new rotational speed. Should the machine be kept operating in this regime for a prolonged time? Why? c) Calculate the output power and the efficiency of the machine in this regime (ignore field winding losses).

A separately excited DC motor drives a constant torque mechanical load. The armature resistance is 0.20 and the nominal armature current is la=74A. The nominal rotational speed of the motor is 1150 rpm. The armature winding is supplied from a 220V DC source. Rotational losses can be neglected. a) What is the load torque if the machine draws the nominal armature current while running at the nominal rotational speed? b) Under the same load, the field winding current is decreased by 20%. Calculate the new rotational speed. Should the machine be kept operating in this regime for a prolonged time? Why? c) Calculate the output power and the efficiency of the machine in this regime (ignore field winding losses).

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
Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...
See similar textbooks
icon
Related questions
Question
A separately excited DC motor drives a constant torque mechanical load. The armature resistance is 0.20 and the nominal armature current is la=74A. The nominal rotational speed of the motor is 1150 rpm. The armature winding is supplied from a 220V DC source. Rotational losses can be neglected. a) What is the load torque if the machine draws the nominal armature current while running at the nominal rotational speed? b) Under the same load, the field winding current is decreased by 20%. Calculate the new rotational speed. Should the machine be kept operating in this regime for a prolonged time? Why? c) Calculate the output power and the efficiency of the machine in this regime (ignore field winding losses). d) With the same load, the field winding voltage is increased back to the nominal value. If the armature winding voltage is decreased to 180V, calculate the new rotational speed. e) Sketch the motor and the load torque-speed characteristics for the conditions in a), b) and d). Indicate operating points (w,T) in all three cases.
Transcribed Image Text:A separately excited DC motor drives a constant torque mechanical load. The armature resistance is 0.20 and the nominal armature current is la=74A. The nominal rotational speed of the motor is 1150 rpm. The armature winding is supplied from a 220V DC source. Rotational losses can be neglected. a) What is the load torque if the machine draws the nominal armature current while running at the nominal rotational speed? b) Under the same load, the field winding current is decreased by 20%. Calculate the new rotational speed. Should the machine be kept operating in this regime for a prolonged time? Why? c) Calculate the output power and the efficiency of the machine in this regime (ignore field winding losses). d) With the same load, the field winding voltage is increased back to the nominal value. If the armature winding voltage is decreased to 180V, calculate the new rotational speed. e) Sketch the motor and the load torque-speed characteristics for the conditions in a), b) and d). Indicate operating points (w,T) in all three cases.
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 4 steps with 3 images

SEE SOLUTIONCheck out a sample Q&A here
Blurred answer
Knowledge Booster
Speed control of motor
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, electrical-engineering and related others by exploring similar questions and additional content below.
Recommended textbooks for you
Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
Electrical Engineering
ISBN:
9780133923605
Author:
Robert L. Boylestad
Publisher:
PEARSON
Delmar's Standard Textbook Of Electricity
Delmar's Standard Textbook Of Electricity
Electrical Engineering
ISBN:
9781337900348
Author:
Stephen L. Herman
Publisher:
Cengage Learning
Programmable Logic Controllers
Programmable Logic Controllers
Electrical Engineering
ISBN:
9780073373843
Author:
Frank D. Petruzella
Publisher:
McGraw-Hill Education
Fundamentals of Electric Circuits
Fundamentals of Electric Circuits
Electrical Engineering
ISBN:
9780078028229
Author:
Charles K Alexander, Matthew Sadiku
Publisher:
McGraw-Hill Education
Electric Circuits. (11th Edition)
Electric Circuits. (11th Edition)
Electrical Engineering
ISBN:
9780134746968
Author:
James W. Nilsson, Susan Riedel
Publisher:
PEARSON
Engineering Electromagnetics
Engineering Electromagnetics
Electrical Engineering
ISBN:
9780078028151
Author:
Hayt, William H. (william Hart), Jr, BUCK, John A.
Publisher:
Mcgraw-hill Education,
SEE MORE TEXTBOOKS