Calculating Field Current and Resistance for a DC Motor

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SUMMARY

The discussion focuses on calculating the field current and resistance for a separately excited DC motor rated at 6W, 120V, and 1500rpm. The field winding resistance (Rfw) is specified as 100Ω. To determine the field current (If), the equation Vf = If * Rfw is utilized, where Vf is the field voltage. Additionally, the resistance required for the field circuit (Rfc) can be derived using power equations P = I * E and P = I² * R. The participants confirm that these equations provide sufficient information to solve for both If and Rfc.

PREREQUISITES
  • Understanding of DC motor principles and operation
  • Familiarity with Ohm's Law and power equations
  • Knowledge of electrical resistance and current calculations
  • Basic skills in circuit analysis
NEXT STEPS
  • Study the relationship between voltage, current, and resistance in DC circuits
  • Learn about the characteristics and equations governing separately excited DC motors
  • Explore advanced power equations and their applications in electrical engineering
  • Investigate methods for calculating field resistance in various motor configurations
USEFUL FOR

Electrical engineering students, motor control engineers, and anyone involved in the design or analysis of DC motors will benefit from this discussion.

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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\Omega.
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?
 
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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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