DC Machines

  • Thread starter Vagrant
  • Start date
  • #1
195
1

Homework Statement


A dc machine(6W, 120V,1500rpm) is separately excited and delivers rated current at rated terminal voltage.Field winding is connected to 120V supply. Rfw=100[tex]\Omega[/tex].
a) Determine the value of field current
b) Determine the value of Rfc required.


Homework Equations


Vf= IfRf


The Attempt at a Solution


In the question the value of Vf is given, while both If and Rf are variables. So I need another relation to find out both the values. Is there another relation that I'm missing?
 

Answers and Replies

  • #2
360
21
Unless I misunderstand the problem, you can get everything you need from the power equations P=IE and P=I^2*R.
 

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