# How to calculate the resistance of a lap wound armature?

• Neil Hayes
In summary, the conversation discusses the calculation of resistance for a 4 pole lap wound armature with 16 coils, each with a resistance of 0.1 ohms. The two diagrams in the lesson lead to different potential answers, with one suggesting a total resistance of 1.6 ohms and the other suggesting 0.1 ohms with 4 parallel paths. After discussing, it is determined that the latter is the correct answer.
Neil Hayes

## Homework Statement

A 4 pole lap wound armature has 16 coils, each with a resistance of 0.1 ohms. Calculate the resistance of the armature?

## The Attempt at a Solution

Hi there fellow members,

I'm currently doing a section of my course which deals with Electrical machines. The lesson that I am on at the moment is dealing with Armature windings ( lap and wave ).

There are two diagrams in the lesson but they are confusing.

One leads me to think that the total resistance would be 16*.01 ='s 1.6 ohms

The other one leads me to think that there are 4 parallel paths. 4*4 = 16

4*0.1=0.4 so total resistance is

1/R = (1/0.4)*4

R = 1/10

R = 0.1 ohms

With the fact that it's a question being asked I would think that the 1.6 is a bit straight forward so I'm leaning towards the 0.1 ohms answer.

Any help/suggestions would be greatly appreciated :)

Neil

P.S Thanks for taking the time to read the question!

Neil Hayes said:
The other one leads me to think that there are 4 parallel paths. 4*4 = 16

4*0.1=0.4 so total resistance is

1/R = (1/0.4)*4

R = 1/10

R = 0.1 ohms
That's correct.

Neil Hayes
cnh1995 said:
That's correct.
Thanks cnh1995 :)

Do you mind if I ask why we have 4 parallel paths? Is this standard for a 4 pole lap wound armature? Having the answer is good but understanding why is the best thing and my lesson notes are fairly unclear, to say the least!

## 1. How do I calculate the resistance of a lap wound armature?

To calculate the resistance of a lap wound armature, you will need to know the length and cross-sectional area of the wire used in the winding, as well as the resistivity of the wire material. The formula for resistance is R = (length x resistivity) / cross-sectional area. You can also use a multimeter to directly measure the resistance of the armature.

## 2. What is the purpose of calculating the resistance of a lap wound armature?

Calculating the resistance of a lap wound armature is important for determining the efficiency of the armature and ensuring that it can handle the required amount of current. It is also necessary for troubleshooting any potential issues with the armature.

## 3. How does the resistance of a lap wound armature affect its performance?

The resistance of a lap wound armature affects its performance by determining the amount of current that can flow through it. A higher resistance means that more energy will be lost as heat, leading to lower efficiency and potentially causing the armature to overheat.

## 4. Is the resistance of a lap wound armature constant?

No, the resistance of a lap wound armature is not constant. It can vary depending on factors such as temperature, material properties, and the number of turns in the winding. It is important to regularly check and re-calculate the resistance to ensure the armature is functioning properly.

## 5. Can I use the same formula to calculate the resistance of a lap wound armature for different wire materials?

No, the formula for calculating resistance will vary depending on the material of the wire used in the armature winding. Different materials have different resistivity values, so make sure to use the appropriate formula for the specific wire material being used.

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