Once at the beginning of the last century in the United States was popular advertising on the theme of "silent servant." The question concerned electricity, or rather, its ability to silently perform various tasks. General Electric thus sought to draw consumer attention to household appliances. But if we touch on the purely physical process of electricity, it turns out that it is not so "silent". An example is the well-known transformer device, which is capable of emitting a rather loud hum. So why is the transformer humming?
How does a transformer work?
To understand this, it does not bother to recall the school physics lesson, which describes the principle of operation of the transformer. The transformer operates on the basis of the law of electromagnetic induction. It includes coils wound with a wire of different diameters and with a different number of turns. These coils represent the primary and secondary windings of the transformer. There is a connection between the windings. It is carried out through a kind of ring made of special ferromagnetic steel. The ring is called the core and is located inside the windings. The core design itself is assembled from thin plates.
When an alternating current is supplied to the primary winding, it creates a magnetic field in the core. This field also changes according to the law of change of the current that generated it. In turn, the field induces an emf of induction in the secondary winding - a converted electric current.
The core material is divided into many micro-sites. In each such section, without the presence of an input voltage, its own magnetic field is present, often directed oppositely to each other. However, under voltage, all flows begin to rush in one direction, creating a powerful magnet. All this is accompanied by a change in the physical dimensions of the core itself. You can now guess why the transformer is buzzing.
Magnetostriction effect
Since the field is variable, the core plates begin to shrink and stretch to the beat with it. This process is called magnetostriction. Such movements are made with a high frequency of 100 Hz, with a current frequency of 50 Hz, vibration emanates into space, which has a sound range and is distinguishable by the human ear. In addition to the standard frequency, in the composition of the alternating current there are higher-frequency harmonics. There are more of them, the more the transformer is loaded, and this, in turn, is more sharp and audible vibration. That's why the transformer is buzzing.
Other causes of transformer noise
But not all reasons for the "talkativeness" of the transformer are hidden in magnetostriction. Why is the loaded transformer humming? Emit noise:
- Winding transformer. This is due to the fact that the magnetic flux is trying to shift the windings relative to the core. The sound is amplified in the case of a poorly wound coil, if the turns do not fit well together.
- Core plates. Why? The transformer very often buzzes when they are poorly fitted and have gaps between flat surfaces. Then, besides squeezing, noise is heard from the ringing of metal.
- Defect or damage to the insulation of the copper wire. This can happen in the thickness of the winding, where elevated temperatures occur. In this case, a spark accompanied by a click may slip between the windings. The more powerful the discharge, the more characteristic and louder the sound.
- Why all the loose parts in the transformer? The transformer is buzzing at work, as they rattle.
In order to avoid this drawback in transformers, silent transformers have been developed. Their circuit is constructed in such a way that the current frequency is converted (increased) to a level at which vibration is not perceived in the sound range. It is 10 kHz and higher. Silent transformers are much smaller in size and weight than conventional ones.
Conclusion
In order not to ask yourself the question of why the transformer is buzzing, all powerful models need to be taken from high-quality, reputable manufacturers. Low-power are not so exacting to accuracy of execution. But if, nevertheless, the existing transformer makes noise during operation, you can try to eliminate it by tightening the plates with the screws. Just try not to overdo it or stratify the core metal. If there are no bolts, use varnish or glue, which fill the core. The rattling of the windings can be eliminated only by rewinding them.