A d.c. shunt motor after running for several hours on constant voltage mains at 400 V takes a field current of 1.6 A. If the temperature rise is known to be 40°C, what value of extra circuit resistance is required to adjust the field current to 1.6 A when starting from cold at 20°C? Temperature coefficient = 0.0043/°C at 20°C. [36.69 0]

A d.c. shunt motor after running for several hours on constant voltage mains at 400 V takes a field current of 1.6 A. If the temperature rise is known to be 40°C, what value of extra circuit resistance is required to adjust the field current to 1.6 A when starting from cold at 20°C? Temperature coefficient = 0.0043/°C at 20°C. [36.69 0]

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter30: Dc Motors

Section: Chapter Questions

Problem 3RQ

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Concept explainers

DC Series Motors

A DC motor is a type of electric motor which converts electric energy into mechanical energy. The forces that are produced by the magnetic field are what those common types of motors rely upon. Either electro-mechanical or electronic, all types of DC motors have some internal mechanism to change the current direction in part of the DC motors. As the DC motors could be powered from existing DC lighting power distribution systems, these motors were the first form of motors widely used. By changing the strength of the current in its field winding or by using a variable supply voltage, the speed of the DC motors can be controlled over a wide range.

Question

A d.c. shunt motor after running for several hours on constant voltage mains at 400 V takes a field
current of 1.6 A. If the temperature rise is known to be 40°C, what value of extra circuit resistance
is required to adjust the field current to 1.6 A when starting from cold at 20°C? Temperature
coefficient = 0.0043/°C at 20°C.
[36.69 0]

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