Math Problem Statement

A shunt generator has an induced emf of 254 V. When the generator is loaded, the terminal voltage is 240 V. Neglecting armature reaction, find the load current if the armature resistance is 0.04 ohm and the field circuit resistance is 24 ohms.

Solution

We can solve this problem step-by-step by considering the electrical circuit of the shunt generator.

Given:

  • Induced EMF (EE) = 254 V
  • Terminal voltage (VtV_t) = 240 V
  • Armature resistance (RaR_a) = 0.04 Ω
  • Field circuit resistance (RfR_f) = 24 Ω

Formula:

The total load current (ILI_L) is the sum of the armature current (IaI_a) and the field current (IfI_f): IL=Ia+IfI_L = I_a + I_f

Step 1: Calculate the field current (IfI_f):

The field current is calculated using the terminal voltage (VtV_t) and the field circuit resistance (RfR_f): If=VtRfI_f = \frac{V_t}{R_f} If=24024=10AI_f = \frac{240}{24} = 10 \, \text{A}

Step 2: Calculate the armature current (IaI_a):

The relationship between the induced EMF (EE), terminal voltage (VtV_t), and armature current (IaI_a) is given by: E=Vt+IaRaE = V_t + I_a R_a Rearranging to solve for IaI_a: Ia=EVtRaI_a = \frac{E - V_t}{R_a} Ia=2542400.04=140.04=350AI_a = \frac{254 - 240}{0.04} = \frac{14}{0.04} = 350 \, \text{A}

Step 3: Calculate the load current (ILI_L):

Substitute IaI_a and IfI_f into the equation for ILI_L: IL=Ia+IfI_L = I_a + I_f IL=350+10=360AI_L = 350 + 10 = 360 \, \text{A}

Final Answer:

The load current (ILI_L) is 360 A.


Would you like further clarification or details? Here are five related questions to deepen your understanding:

  1. How does armature reaction affect the terminal voltage in practical scenarios?
  2. What is the effect of increasing field resistance on the load current?
  3. Can this problem be solved if armature reaction were not neglected?
  4. How would the load current change if the armature resistance were doubled?
  5. What is the efficiency of the generator under these conditions?

Tip: Always check the calculated field and armature currents separately to avoid errors when combining them for load current calculations.

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Math Problem Analysis

Mathematical Concepts

Electrical Engineering
Ohm's Law
Circuits

Formulas

I_L = I_a + I_f
I_f = V_t / R_f
I_a = (E - V_t) / R_a

Theorems

Kirchhoff's Voltage Law
Ohm's Law

Suitable Grade Level

College/University Level (Electrical Engineering)