How to solve the hum of the power amplifier transformer

1. The internal core or fixture of the distribution transformer is loose, the sound becomes louder, and there is intermittent noise. After testing, the load current is not large, the temperature is not high, the secondary no-load voltage is basically balanced, and the operation is not monitored; If the sound continues to increase, you should consider replacing it for maintenance.

2. The system is far away from the short circuit or grounding, and the fused piece is not fused in time (due to the short-circuit current.

is not too large or the fused installation capacity is too large), under the action of short-circuit current, due to the magnetic flux.

The magnetic circuit is severely unbalanced, and a strong and uniform noise occurs.

3. When the inter-turn short circuit, the short circuit turns will produce serious local overheating, which will prompt the transformer oil.

Locally boiling, "gurgling, gurgling" like the sound of boiling a pot occurs. The tap-changer has poor contact or insulation breakdown, and the "crackling" sound of discharge occurs. In this case, there will be a serious imbalance in the no-load voltage of the measurement and distribution variable, and the oil temperature will also rise.

The distribution transformer should be stopped and sent to the factory for maintenance.

Judgment and elimination of humming fault of power amplifier: 1. AC sound. Turn on the speaker, and turn off the volume potentiometer to the end to the silent state, at this time the speaker continues to hum, first check whether the four rectifier diodes in the power supply circuit are intact, if they are intact, it means that the power amplifier circuit in the power filter capacitor leakage, the capacity is too small, desoldering, should replace the same type of capacitor, or increase the filter capacity.

As shown in the figure (rectifier diode and filter capacitor circled in red): 2. As the volume increases, the hum also increases, which means that the noise is in the pre-amp, first of all, unplug the audio source input wire, and then turn the volume up, if not, it is a problem with the audio input shielding wire, repair or replacement. 3. After unplugging the audio cable, there is a buzzing sound, which means that the voltage amplification circuit of the pre-amplifier is faulty and needs to be repaired by the master.

The power transformer will produce AC sound if the magnetic flux leakage is smaller, the power filter capacitor capacity will be smaller, the power amplifier quiescent current will be seriously large and will produce AC sound, the signal line will be shielded poorly AC sound, the grounding terminal will not be in accordance with the principle of one point grounding will produce AC sound, and external interference will also produce AC sound when it enters the power supply. There are many reasons for this.

The sound of electrical current emitted by the distortion of the amplifier.

1.Check whether the signal input ground is good?

2.Is the sound too loud? Most of the amplifiers on the market are Class B amplifiers, and the volume will be distorted when the volume is adjusted above 50%.

3.The power amplifier works for a long time under the condition of poor heat dissipation, which leads to the super stability of the power amplifier tube, and it will also be distorted.

There are many reasons for this, such as abnormal performance of filter capacitors, poor grounding of circuit boards, aging of audio lines, etc.

A continuously and evenly "humming" sound occurs in a normal operating transformer. This is because when the alternating current passes through the windings of the transformer, it generates a periodically varying alternating magnetic flux in the core, and as the magnetic flux changes, it causes the core to vibrate and emit a uniform "humming" sound. If the sound is uneven or there are other abnormal sounds, it is an abnormal sound.

Changes in sound can reflect abnormalities inside or outside the transformer to some extent.

1) The transformer emits a uniform and heavy "hum" sound, without noise, which may be caused by the increase in the load of the transformer. The "buzz" is loud or sharper than usual, but the sound is even, which may be caused by too high a supply voltage. It should be handled on a case-by-case basis.

2) The transformer emits a short-term "wow" sound, which is short and recovers quickly, which may be caused by the impact of large current on the transformer, such as system failure, start of large power equipment, sudden change in load, etc., which should be judged in combination with system parameter changes (such as voltmeter and ammeter data).

3) The transformer emits a "hissing" sound, and at night or in rainy weather, you can see a blue corona near the transformer bushing, which may be due to serious porcelain pollution and other reasons for corona discharge on the surface of the bushing.

The humming sound of the transformer is mostly caused by loose laminations. You'll need to reinsert the tabs and make sure they're plugged in sufficiently, and if necessary, insulating glue potting.

On the one hand, the abnormal noise comes from external factors.

1.There is an overvoltage situation in the power grid. Generally speaking, when a single-phase grounding or electromagnetic resonance occurs in the power grid, an overvoltage is triggered, resulting in a sharper sound than usual.

2.The overcurrent situation in the power grid is generally caused by overload, large power load, traversal short circuit, etc. The occurrence of the above two situations is generally abnormal with the indication of the instrument (voltmeter or ammeter), which is easier to distinguish.

3.The transformer is running at overload. The load changes greatly, and due to the harmonic effect, the transformer will emit a "high tone, high volume" abnormal sound, indicating that the instrument pointer will swing.

4.Partial discharge of transformer. When the drop-out fuse or tap-changer of the transformer is not in good contact, the local heating will also cause abnormal noise; When the transformer bushing of the transformer is dirty, the enamel of the surface transformer falls off or there are cracks, a noise similar to "hissing" will also be heard.

5.Weather reasons. In foggy weather, snow and other special weather, corona discharge and glow discharge may occur at the casing, and small blue sparks may be seen at night, which may also cause abnormal noise.

One aspect of the abnormal noise can come from the problem of the transformer itself.

1.There is a problem with the process of the transformer. If the dipping paint of the transformer is not dried properly, the magnetic core will not be firm, which will cause mechanical vibration and abnormal noise; The air gap length of the transformer is not suitable, which will lead to the instability of the working state of the transformer, resulting in abnormal noise; Loose individual clamps or screws can also cause abnormal noises.

2.There is a problem with the loop of the transformer. Improper wiring of the transformer circuit board will cause interference, resulting in abnormal noise; Improper parameter setting of the feedback loop will lead to the instability of the loop, resulting in the generation of oscillation and abnormal noise. There is a problem with the quality of the components in the loop, such as the poor quality of the power MOS tube, etc., which leads to the oscillation causing noise.

3.There is a problem with the core of the transformer. When the core of the transformer is saturated, the current in the coil will increase and cause the transformer to heat up, which will cause self-oscillation, and the coil oscillation will cause the surrounding air to vibrate, so it will make abnormal noise.

When it comes to power regulation, transformers are everything. Step-up and step-down transformers can raise or decrease the voltage to apply any power level required for a given application, and they will work reliably and efficiently as long as the transformer noise is not part of the electrical system.

But transformer noise can be a significant problem. Even a small amount of noise can hinder engineering and prevent power transformers from working the way they are designed, so it's important to understand exactly what transformer noise is, what causes it, and how to prevent it.

Below is a review of these three elements of transformer performance, along with some appropriate recommendations and a review of two of the best transformer products in the industry.

What causes a transformer to hum?

One of the most common symptoms of excessive transformer noise is the familiar hum of the transformer. But determining if the amount of noise is too loud is much more complicated than it sounds.

Why? Because all transformers "hum" to some extent, because the alternating current passes through the transformer, it has a magnetic effect on the core of these devices.

Some level of hum is normal, but if the transformer's performance measurements exceed the specified parameters for current, voltage, or both, steps need to be taken to control it. In some work situations, it is also necessary to do so in order to keep workers more effective and productive.

Let's look at some strategies you can use to reduce or eliminate the buzz, starting with some steps you can take during the installation and installation process.

1.When a high-capacity electrical device is started, the load current is high, which causes the transformer to become louder. 2.

When the transformer is overloaded, it emits a loud humming sound. 3.When the system is shorted or grounded, the transformer generates a lot of noise at high short-circuit currents.

4If the transformer is equipped with a thyristor rectifier or an electric arc furnace, the higher harmonics generated by the transformer will also increase the sound of the transformer.

After the power transformer is fed with alternating current, if the core is not fixed, it is easy to "hum" low-frequency sound. How does this low-frequency sound come about? As we all know, when the power transformer is connected to the alternating current, an alternating magnetic field will be generated, and the characteristics of the electromagnetic field have hysteresis, that is to say, when the power supply is disconnected, the magnetic field has not disappeared immediately, and continues to maintain for a period of time.

The polarity of the alternating magnetic field is constantly changing, and it is easy to form a maximum collision of ns, that is, the state of same-sex repulsion and alien-shaped attraction.

1.After the large-capacity power supply equipment is started, the load current is large, and the transformer sound increases. 2.

When the transformer is overloaded, it emits a high, heavy humming sound. 3.When the system is shorted or grounded, the transformer generates a lot of noise through large short-circuit currents.

4.If the transformer is equipped with a device such as a thyristor rectifier or an electric arc furnace, the sound of the transformer will also become louder due to the generation of higher harmonics.

After the transformer is energized, there will be an electric current in the coil, and if there is an electric current, there will be an electromagnetic force interaction, and the magnitude of the alternating current will change, and the electromagnetic force will also change, so there will be vibration, so there is a humming sound.

1. When starting the large-capacity power equipment, the load current is larger, which makes the transformer sound bigger.

2. When the transformer is overloaded, it emits a very high and heavy humming sound.

3. When the system is short-circuited or grounded, through a large short-circuit current, the transformer will produce a lot of noise, 4. If the transformer is equipped with thyristor rectifier or electric arc furnace and other equipment, the transformer sound will also become louder due to the generation of higher harmonics.

According to your description, the noise of the transformer is generally caused by the alternating electromagnetic field of the transformer.

We hope you find ours helpful.

The power amplifier has a buzzing current sound. Workaround:1.

Electromagnetic interferenceElectromagnetic interference is mainly divided into power transformer interference and stray electromagnetic interference. Power transformer interference: Due to the magnetic flux leakage of the power supply, if conditions permit, the effect of installing a shielding cover for the transformer is very obvious, which can block the magnetic flux leakage to the greatest extent.

The shield is preferably made of iron (the shield must be grounded). 2.Check that the various wirings are in good contact.

There should be no broken wires or contact with the amplifier housing. Do not tie the wires together with tie wires. Use high-quality wires and tighten the wiring position (or solder firmly).

3.When the audio input is not connected, and the input plug is not plugged in, whether there is communication sound is usually a problem with the machine. For problems in the machine, check if the filter circuit is effective, measure the capacity of the filter capacitor, or test the capacitor of the same capacity in parallel.

A good capacitor can solve this problem. 4.The shield from the audio input socket to the amplifier input should be grounded at one end.

Don't use its shielding layer as the low end of the signal to transmit audio signals, which are prone to alternating sounds. 5.The current sound emitted by the power amplifier may be caused by the poor contact between the input circuit of the power amplifier or the previous circuit and the "ground".

For example, the volume potentiometer ground terminal is loose, the housing is poorly grounded, and the common end of the pre-amp to post-amp signal line is broken or poorly contacted. The excessive quiescent current of the final amplifier tube of the ordinary power amplifier circuit will also cause current sound.

The power amplifier has a buzzing current sound. Solution: 1. Electromagnetic interference.

Electromagnetic interference is mainly divided into power transformer interference and stray electromagnetic wave interference. Power transformer interference: Due to the magnetic flux leakage of the power supply, the effect of installing a shielding cover for the transformer is very obvious when conditions permit, which can block the magnetic flux leakage to the greatest extent.

The shield cover should preferably be made of iron material (the shield cover must be grounded). 2. Check whether the various wiring is in good contact. There must be no broken wires or wires in contact with the power amplifier housing.

Do not tie the wires together with a strapping wire. Use a high-quality wire and tighten the wiring position (or weld firmly). 3. When the audio input is not connected and the input plug is not plugged in, whether there is AC sound is usually a problem with the machine.

For problems in the machine, check whether the filter circuit is effective, measure the capacity of the filter capacitor, or test in parallel with capacitors of the same capacity. A good capacitor can solve this problem. 4. The shielding wire shield from the audio input socket to the input end of the power amplifier should be grounded at one end.

Don't use its shield as the low end of the signal to transmit the audio signal, which can easily produce communication sound. 5. The sound currently emitted by the power amplifier may be due to poor contact with the "ground" in the input circuit or the previous circuit of the power amplifier. For example, the volume potentiometer ground terminal is loose, the housing is poorly grounded, and the common terminal of the pre-amp to post-amp signal line is broken or poorly contacted.

Excessive electrostatic current of the final amplifier tube of an ordinary power amplifier circuit will also cause current sound.