Calculating magnetomotive force in a transformer

[bitrex]

If I have a transformer with a known primary inductance and number of turns, and the output is open circuited, how would I go about calculating the magnetomotive force created by the magnetizing current?

 

[Bob S]

You can determine the B field in the transformer by equating the engineering and physics version of the stored energy:
(1/2) L I² = (1/2) ∫ B H dV

where L = inductance, I = current, B = u u₀ H, B=Tesla, H=amp-turns per meter, V = integral over volume of iron, u = relative permeability, u₀ = 4 pi x 10^-7 Henrys per meter..

∂ ∫ ∏ ∑

 

[oswaler]

To calculate the magnetomotive force in a transformer, we need to use the equation MMF = N * I, where N is the number of turns and I is the current in the primary winding. In this case, since the output is open circuited, there is no load current, and the only current flowing through the primary winding is the magnetizing current.

To calculate the magnetomotive force, we first need to determine the value of the magnetizing current. This can be done by using the primary inductance and the applied voltage. The equation for calculating the magnetizing current is I = V / ωL, where V is the applied voltage, ω is the angular frequency, and L is the primary inductance.

Once we have the value of the magnetizing current, we can then use the equation MMF = N * I to calculate the magnetomotive force. This will give us a measure of the magnetic field strength created by the transformer.

It is important to note that this calculation assumes that the transformer is ideal and there are no losses. In real-world scenarios, there will be some losses, which will affect the accuracy of the calculated magnetomotive force. Additionally, the magnetomotive force will vary depending on the load connected to the secondary winding. Therefore, it is important to consider these factors when calculating the magnetomotive force in a transformer.