# Determine the shunt field current in a magnetic circuit

• Engineering
• Fatima Hasan
In summary, the problem statement discusses finding the flux density, permeability, and reluctance of an iron material while ignoring fringing and leakage effects. The conversation then delves into the assumption that the flux path has a net cross-sectional area of 200 cm^2 and the confusion surrounding the uniformity of this cross-section throughout the magnetic path. Ultimately, it is suggested that if a uniform magnetic flux density is not the primary concern, then case 1 (where the area is uniform throughout the magnetic path) would be the practical choice due to other factors such as mechanical strength and reducing losses.
Fatima Hasan
Homework Statement
Written below.
Relevant Equations
Equations are attached below.
Problem Statement :

Here's my attempt :
* By assuming that the fringing and leakage effects are ignored.

I find the flux density , the permeability and the reluctance of the iron , but then I get stuck .
Any help would be greatly appreciated .

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I tried to solve it , and that's what I got :
Analog Circuit :

That's what I got , but I am not sure if my answer is correct or not .
I want to confirm my answer .

The statement states that the flux path has a net cross-sectional area of 200 cm^2.
Based on this statement, I am a bit confused about the assumption that the cross-sectional area of left branch and right branch of the toroidal core are the same as the cross-sectional area of the air gaps.

Last edited:
alan123hk said:
The statement states that the flux path has a net cross-sectional area of 200 cm^2.
Based on this statement, I am a bit confused about the assumption that the cross-sectional area of left branch and right branch of the toroidal core are the same as the cross-sectional area of the air gaps.
Yes it's not given. So I would assume the cross-section is uniform thruout the magnetic path, the drawing strongly suggesting otherwise notwithstanding.

I agree with alan123hk: the "path" has to be the area for indicated path. That means the pole area has to be double=400 cm^2
Then n*I=Hfe*Lfe+B/μo*2*airgaplengs [n=number of turns]

Case 1 : the area is uniform throughout the magnetic path
Case 2 : the area of the pole is twice that of the left/right branch

Assume that the entire magnetic circuit has the same BH curve characteristics

In case 1, the B in the pole is twice that of the B in the left/right branch, and since the pole becomes bottleneck, the maximum magnetic flux density in the left/right branch may not be fully utilized.

In case 2, the entire magnetic circuit has the same B everywhere, there is no bottleneck, and the maximum magnetic flux density can be achieved throughout the entire magnetic circuit.

Of course, if uniform magnetic flux density is not the primary concern, then case 1 is still the choice in practical applications, since there may be many other factors to be considered, such as mechanical strength and reducing eddy current/hysteresis loss.

Last edited:

## 1. What is a shunt field current in a magnetic circuit?

A shunt field current is the current that flows through a parallel branch of a magnetic circuit. It is typically applied to control the magnetic field strength and direction in the circuit.

## 2. How is the shunt field current calculated?

The shunt field current can be calculated using Ohm's Law, where the current is equal to the voltage divided by the resistance. In a magnetic circuit, the resistance is typically represented by the reluctance of the material.

## 3. What factors affect the shunt field current?

The shunt field current is affected by the voltage applied, the resistance of the circuit, and the amount of magnetic flux desired in the circuit. Changes in any of these factors can result in a change in the shunt field current.

## 4. How does the shunt field current impact the behavior of a magnetic circuit?

The shunt field current plays a crucial role in controlling the magnetic field strength and direction in a circuit. It can be used to adjust the amount of magnetic flux present, which affects the performance and efficiency of the circuit.

## 5. What are some practical applications of determining the shunt field current in a magnetic circuit?

Determining the shunt field current is essential in designing and operating various electrical devices such as generators, motors, transformers, and solenoids. It allows for precise control of the magnetic field and, therefore, the performance of these devices.

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