How do you stop transformer hum?

Answer 1

1. THE INSULATION IS DETERIORATING

2. LOOSE TERMINATIONS

3. NO RUBBER FOOTING INSTALLED

4. OVERLOADING / UNBALANCED LOADING

5. Magnetostriction. When the core becomes magnetised, it expands, then it contracts and expands again as the field is reversed. A 50Hz transformer therefore expands and contracts at 100Hz, producing a sound at that frequency.

Answer 2

A perfect transformer doesn't hum. Unfortunately generally they aren't perfect. The coils inside the transformer are sometimes connected to each other via metal plates which transfer the magnetic field. This magnetic field changes direction as the poles from an alternating current does. And that in turn can make the plates wobble. This wobbling is equal to the clockrate of the alternating current. Which is the frequence of the humming sound you hear. (Where I live home sockets have a clockrate of 50Hz, meaning [certain] transforms can create a hum with a 50Hz frequency).

A transformer hums due to the magnetic field produced in the iron core causing the core material and the windings to vibrate at 120Hz. In order words as a typical transformer operates at 60hz, the magnetic field is also switched causing the magnetic field in the winds to change directions. This rapid change in the magnetic field causes a vibration in the core and windings causing a bee like hum. Magnetostriction is the proper term used to describe this behavior.

The core of a transformer is made of laminated layers of iron material. This type of construction makes it work more efficiently. The Alternating Current (AC) repeatedly magnetizes and demagnetizes the layers in the core causing them to vibrate. The layers are bound together with some sort of glue limiting the actual vibrations and if properly done there is no humming sound. As the ballast gets older, the glue material weakens allowing the layers to separate and allowing the vibrating layers to hit each other resulting in the humming sound. An old transformer can get pretty loud.

Alternative Answer An expression widely used within the electricity industry is that Transformers hum because 'they don't know the words'!

Answer 3

Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when magnetized. When the magnetization is taken away, it goes back to its original condition. This phenomenon is scientifically referred to as magnetostriction. A transformer is magnetically excited by an alternating voltage and current so that it becomes extended and contracted twice during a full cycle of magnetization.

The magnetization of any given point on the sheet varies, so the extension and contraction is not uniform. A transformer core is made from many sheets of special steel to reduce losses and moderate the ensuing heating effect. The extensions and contractions are taking place erratically all over a sheet and each sheet is behaving erratically with respect to its neighbor, so you can see what a moving, writhing construction it is when excited. These extensions are miniscule proportionally and therefore not normally visible to the naked eye. However, they are sufficient to cause a vibration, and consequently noise. Applying voltage to a transformer produces a magnetic flux, or magnetic lines of force in the core. The degree of flux determines the amount of magnetostriction and hence, the noise level.

Answer 4

The reason why electric wires hum is due to the production of corona discharge. This may also be due to magnetostriction among other causes. .