# Transformers and iron cores and frequency

• IWantToLearn
In summary: In a small transformer, the frequency of the secondary voltage will remain the same as the frequency of the primary voltage. In summary, the main factor in mutual inductance is the rate of change of current in the primary coil. The use of a soft iron core increases the density of the magnetic field but does not affect the rate of change of current. Soft iron cores are used to reduce hysteresis losses and eddy currents in the transformer core. Eddy currents do not contribute to the secondary voltage frequency.
IWantToLearn
As far as i understand the thing that matter in all of the process of mutual inductance is the rate of change of the current in the primary coil $$\frac{dI}{dt}$$
butting soft iron core will increase the density of the magnetic field inside the primary coil, but how this will effect $$\frac{dI}{dt}$$ , now the question is "What is the reason we use soft iron core?"

Second using these iron cores will create eddy currents, and causes power losses
but could this effect will also cause increasing the frequency of the secondary voltage ?

IWantToLearn said:
As far as i understand the thing that matter in all of the process of mutual inductance is the rate of change of the current in the primary coil $$\frac{dI}{dt}$$
butting soft iron core will increase the density of the magnetic field inside the primary coil, but how this will effect $$\frac{dI}{dt}$$ , now the question is "What is the reason we use soft iron core?"

Second using these iron cores will create eddy currents, and causes power losses
but could this effect will also cause increasing the frequency of the secondary voltage ?

Most power transformer core's are an alloy of Iron and Silicon that has been cold rolled, they're referred to as a "CRGOS" core (Cold Rolled Grain Oriented Silicon Steel). The main goal behind all that is to rid the transformer core of Hysteresis losses: The cold rolling orients the grain of the ferromagnetic material so that hysteresis is kept at a minimum; the addition of silicon was found to also decrease the hysteresis and create a highly permeable material, cutting down on magnetization losses. I've never heard it referred to as "soft iron," but I suppose it could be.

Laminations in the core eliminate much of the eddy currents, but there will always be some present. I view eddy currents as currents that don't really have a rhyme or reason, they're simply a byproduct of losing something from a more useful attribute; they would not add to the voltage of the secondary in any appreciable way.

Last edited:
What about the frequency of the secondary voltage?
it will increase?

IWantToLearn said:
What about the frequency of the secondary voltage?
it will increase?

No. In large scale power systems load currents can cause frequency to fall, but this is due to generator operation and not transformer characteristics.

## 1. What are transformers and why are they important?

Transformers are electrical devices that are used to transfer electrical energy between circuits at different voltage levels. They are important because they allow for efficient transmission and distribution of electricity, as well as voltage conversion for various electronic devices.

## 2. How do transformers work?

Transformers work by using electromagnetic induction to transfer energy between two or more electrical circuits. The transformer consists of two coils of wire, known as the primary and secondary windings, which are wrapped around a core made of iron or other magnetic material. When an alternating current flows through the primary winding, it creates a changing magnetic field that induces a voltage in the secondary winding, resulting in energy transfer.

## 3. What is the role of iron cores in transformers?

Iron cores are an essential part of transformers as they provide a path for the magnetic field to pass through, increasing the efficiency of energy transfer. The iron core is made up of thin, insulated sheets of iron called laminations, which are stacked together to reduce energy loss due to eddy currents.

## 4. How does the frequency of the input signal affect transformers?

The frequency of the input signal has a significant impact on the performance of transformers. Transformers are designed to operate at a specific frequency, and if the input signal has a different frequency, it can lead to a decrease in efficiency and potentially damage the transformer. This is because the changing magnetic field generated by the input signal induces a voltage in the secondary winding, and if the frequency is too high or too low, the induced voltage may not be at the desired level.

## 5. Can transformers be used for DC signals?

No, transformers can only be used for AC signals. This is because transformers rely on the changing magnetic field generated by the input signal to induce a voltage in the secondary winding. In DC signals, the magnetic field does not change, so there is no voltage induced in the secondary winding. However, DC signals can be converted to AC signals using devices such as inverters before being used with transformers.

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