Something You Need to Know About Transformers

Label:High Frequency Transformer, Low Frequency Transformer

Jul 4, 20237080

Something You Need to Know About Transformers

Transformers are important in our daily lives. They exist in the electrical equipment related to power supply. Let's talk about something about transformers.

 

1. Difference between high frequency transformers and low frequency transformers

 

In general, low-frequency transformer refers to "power frequency transformer". It works at 50Hz, and changes the voltage. The iron core used in low-frequency transformer is generally silicon steel sheet with high magnetic permeability.

 

High frequency transformer refers to a transformer that works at high frequency and acts as a transducer. The frequency of the magnetic field is high, eddy currents will be generated in the silicon steel sheet (the conversion speed of the small magnet in the silicon steel sheet cannot keep up), so the high frequency transformer usually use high frequency ferrite as the core.


 

The difference between high frequency transformer and low frequency transformer lies in the difference in frequency. It is the operating frequency, which leads to some differences in material selection. The working principle of the low frequency transformer is the same as that of the high frequency transformer. No matter the operating frequency is high or low, energy is transmitted through electromagnetic induction.

 

Due to the different frequencies, the high one can only be used in circuits with high frequency. And the frequency of the excitation source should match the frequency of the transformer. While the low frequency one is the opposite. If the frequency does not match, it is not available.

 

If the transformer transmits a certain amount of energy, the working frequency is high. The number of energy transmissions within a certain period of time is large, and the energy transmitted each time can be less. The transformer uses less material and the structural size is small. Therefore, high frequency transformers have small number of coil turns. The size can be very small. On the other hand, the number of turns of the low frequency transformer coil is large.

 

For the two transformers at the same power, the high frequency transformer will be much smaller than the low frequency transformer. In this case, the high one will only be about one-tenth of the low one. This is because the low frequency transformer needs to be protected, the u value is reduced. It is made of silicon steel sheet, but the efficiency becomes poor, so a large volume of heat dissipation is required.

 

2. Power amplifier and toroidal transformer

 

 

Nowadays, many electronic enthusiasts choose toroidal transformers when talking about audio power amplifier transformers. The toroidal transformers in audio power amplifiers is determined by the characteristics of audio power amplifiers.

 

Basically different from the power consumption of other devices, the power consumption of audio power amplifiers not only changes rapidly, but also varies greatly. This requires that the transformer must have a strong instantaneous overload capability and a fast response speed. Otherwise, it will easily cause noise, bad sound, and poor sound quality.

 

Due to the large capacity of the toroidal transformer in the same volume, the direct-coupled type has almost zero delay response, which meets the characteristics of audio power supply.

 

3. Isolation transformer

 

Isolation transformer is a transformer with two or more independently separated coils. The primary coil and secondary coil have been completely separated (isolated), and energy is transferred through a magnetic field.

 

Why do we need isolation transformer? It's because of some country's power supply system. When the power supply system supplies low-voltage users, it generally adopts a three-phase four-wire system, and the neutral wire is grounded. The popular point is the wires to the residents' homes. One is the phase wire (live wire), and the other is the neutral wire, which is in the same position as the earth. When the human body touches the hot bottom plate, the current passes through the human body, and form a loop with the earth, causing electric shock.

 

If we use the isolation transformer, it will be safe, because the primary and secondary coils exchange energy through the magnetic field. There is no physical hard connection. Even if the human body touches the charged object, the potential of the charged part will be caused by the same status as the human body and the earth. It is low potential, and will not cause electric shock.

 

Pay attention to two points when using the isolation transformer. One is that both ends of the secondary of the transformer cannot be grounded. The other one is that the human body cannot touch both ends of the secondary at the same time. Otherwise, there is still a risk of electric shock.


 

4. Isolation function of power transformer

 

Many electronic appliances use AC 220V as the power supply. In order to ensure the personal safety of users during the use of the equipment, it is necessary to isolate the 220V AC power supply. At this time, a power transformer is used. At the same time, the power transformer reduces the 220V AC voltage to a suitable voltage.

 

When troubleshooting, it is necessary to contact the components in the circuit or the ground wire in the circuit in the energized state. The danger of electric shock can be prevented by adding a power transformer.


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