How Do You Calculate the Temperature Rise of a Bimetallic Strip in an MCB?

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In summary, the conversation discusses the theoretical calculation of the temperature rise of a bimetallic strip used in an MCB. The speaker has the necessary dimensions and properties of the strip, as well as practical values for current passed. However, the current equation being used does not account for heat loss and the varying resistivity over time. Assistance is requested in correcting the equation by including a convective heat transfer term.
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physiomaniac
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I am studying the bimetallic strip used in MCB.
I am trying to theoretically calculate the temperature rise of the strip when 1.13In (safe value of current for which the MCB shouldnot trip) is passed through the bimetallic strip. I am having the dimensions, resistivity, modulus of elasticity, flexivity, density of the strip.

I even have the practical values with me for ever few secons of current passed.
I tried to use the relation MC(dT)=I^2Rt
that is all the heat generated is used in the temperature rise.
But practically other things need to be considered like heat loss with environment, also the above formula holds good for only few seconds and here the resistivity I have taken constant will also vary.
Please help me out with a relevant solution.
 
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  • #2
To correct the equation being used, one would need to include a convective heat transfer term, using an estimated heat transfer coefficient to the surroundings.
 

Related to How Do You Calculate the Temperature Rise of a Bimetallic Strip in an MCB?

1. How does a bimetallic strip work?

A bimetallic strip is composed of two different metals bonded together, each with different coefficients of thermal expansion. When the strip is heated, one metal expands more than the other, causing the strip to bend towards the side of the metal that expands more.

2. What is the formula for calculating the deflection of a bimetallic strip?

The formula for calculating the deflection of a bimetallic strip is ΔL = αLΔT, where ΔL is the change in length, α is the coefficient of thermal expansion, L is the original length of the strip, and ΔT is the change in temperature.

3. How does the thickness of the bimetallic strip affect its deflection?

The thickness of the bimetallic strip does not directly affect its deflection. However, a thinner strip will have a lower thermal mass, meaning it will heat up and cool down faster, resulting in a quicker response time.

4. What factors can affect the accuracy of bimetallic strip calculations?

The accuracy of bimetallic strip calculations can be affected by factors such as the materials used, the uniformity of the strip's thickness, and the accuracy of the temperature measurement.

5. How can bimetallic strips be used in practical applications?

Bimetallic strips have many practical applications, such as in thermostats, thermometers, and electrical switches. They can also be used in mechanical systems to control the movement of components based on temperature changes.

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