How does a transformer make clicking sounds when being powered ON or when it is bucking/boosting voltages, without having any moving parts inside?


How does a transformer make clicking sounds when being powered ON or when it is bucking/boosting voltages, without having any moving parts inside?

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The transformer still have a coil in it and when you apply a current to the coil the magnetic field generated will make the coil contract and act as a tiny speaker. This is the source of the transformer buzz you often hear. To prevent this switch mode power supplies and buck boost transformers use frequencies that is too high for the human ear to perceive. But you still get various harmonics and effects of heating, especially during startup before the transformer have become stable.

Or it is possible that even your tiny power converter have fitted a small relay in it. You can get quite small surface mounted relays that can easily be integrated into a small power supply for extra protection.

The clicks could be relays inside the module. Relays do have parts that are physically moved back and forth by electromagnets to complete or break the circuit. They typically make a click sound when that moving part snaps into one of its places inside. There might be something with the circuitry that causes the relays to constantly engage and disengage, I don’t know.

Or it could be the noise of arcing. Depending on the kind of transformer and what it’s doing, arcing *could* be a normal and expected thing or it could be a symptom of some defect.

If the clicking is more like buzzing, then it’s just the normal sound ferromagnetic materials sometimes make when they’re inside a strong and constantly changing electromagnetic field.

Why do you think there is no part that moves?

There is no part that should that does not mean there is no part that does move. You have two coils with a lot of wire loops and usually an iron core too. The current creates a magnetic field and then they interact with the other parts you get forces too, that is how electric motors work.

Iron is ferromagnetic and is attracted to magnetic fields. A coil with a current is an electromagnet so there is forces between it and the iron core

The transformer that is mounded to are not rigid bodies, they can bend and the magnetic field result in them doing that to a small degree. That causes the sound you hear.

So parts do move even if it is something we designed them to do, we try to stop them from moving.

Usually electronics that have no moving parts but make noise do so due to the electromagnetism inherent to current and wire that causes something metal to move.

In fact, sometimes things that *appear* to have no moving parts in fact do, insomuch as they deliberately use this magnetic effect to achieve something. For example, relays allow you to use a very low voltage circuit as a switch for a much higher voltage one by having the low voltage circuit create an electromagnetic effect which physically pulls a (hidden but audible) bit of metal such that another, entirely separate circuit is now complete. This way the two circuits remain physically isolated from each other, but this low voltage circuit needs to be maintained for the magnetic effect to hold the other circuit together. But you can hear it clicking on and off!

Some transformers have moving parts. This allows them to adjust for changes in the bulk electric grid while maintainging a set output voltage. They have a mobile tap that can effectivly change how many windings are being used. Basically one side of the transformer has a conection that can move up and down the windings.
Monitoring equipment can make some noise or move about as well.