[Isolation Transformer] The role of isolation transformer, the principle of isolation transformer, and the selection of isolation transformer
The role of isolation transformer
1. Complete electrical insulation between the primary side and the secondary side, and also isolate the circuit. In addition, the high-frequency loss of its core is used to suppress high-frequency clutter from entering the control loop. Using an isolation transformer to float the secondary to the ground can only be used in situations where the power supply range is small and the lines are short. At this time, the system’s capacitance current to ground is too small to cause personal injury.
2. Electrical isolation – one is to protect equipment, and another very important role is to protect personal safety! Isolate hazardous voltages. The output and input capacitance coupling of the isolation transformer is small, and it has a more inhibitory effect on interference caused by lightning, discharge, grid switching, motor starting and other grid noise. It is a relatively effective power supply noise suppressor. From this point of view, the isolation transformer is more protective The role of the equipment. The so-called protection of personal safety refers to the protection of people operating this equipment. Because the electromotive force of the isolation transformer is obtained through secondary induction, it does not form a loop with the primary side (forming a loop with the earth), so it will not cause electric shock.
3. Change the voltage, such as changing the 220V AC voltage to AC 15V, but a greater effect is to separate the 220V GND and the 15V GND, which is very important. We know that when the human body holds the 220V neutral wire and then touches the earth, no current will flow. However, if the human body holds the live wire and then touches the earth, life will be in danger. The isolation transformer plays a very important role in isolating the reference point (i.e. ground). After isolation by the transformer, for example, the voltage is still 220V. As long as the two wires are not in contact with the earth, there will be no problem if any one of the wires in the human hand is connected to the earth.
Principle of isolation transformer
The principle of isolation transformer is the same as that of ordinary transformer. They all use the principle of electromagnetic induction. Isolation transformers generally refer to 1:1 transformers. Since the secondary is discordantly connected. There is no potential difference between any wire of the secondary and ground. Safe to use. Commonly used as maintenance power supply.
Isolation transformers are not all 1:1 transformers. The power supplies for control transformers and tube equipment are also isolation transformers. Power supplies such as tube amplifiers, tube radios, oscilloscopes, and lathe control transformers are all isolation transformers. For example, in order to safely repair color TVs, a 1:1 isolation transformer is commonly used. Isolation transformers are commonly used and are also used in air conditioners.
Although there is an isolation circuit between the primary and secondary windings of a general transformer, at higher frequencies, the capacitance between the two windings will still cause electrostatic interference between the circuits on both sides. In order to avoid this interference, the primary and secondary windings of the isolation transformer are generally placed on different cores toReduce the capacitance between the two; some also use the primary and secondary windings to be placed concentrically, but add electrostatic shielding between the windings to obtain high anti-interference characteristics.
Electrostatic shielding is to set a piece of unclosed copper sheet or non-magnetic conductive paper between the primary and secondary windings, called a shielding layer. The copper sheet or non-magnetic conductive paper is connected to the housing with wires. Sometimes in order to achieve better shielding effect, the entire transformer is also covered with a shielding shell. The lead-out terminals of the winding are also shielded to prevent other external electromagnetic interference. In this way, only magnetic coupling remains between the primary and secondary windings, and the equivalent distributed capacitance between them can be less than 0.01pF, thereby greatly reducing the capacitive current between the primary and secondary windings and effectively suppressing the power supply and other circuits. All kinds of interference.
Isolation transformer selection
1. Look at the appearance
Good quality transformers generally look like Relatively clean and pollution-free, the metal material is not warped, the insulating tape is neatly wound, the leads (or pins) are well fixed, the labels are well printed, and the adhesion is neat.
2. Look at the logo and packaging
The logo of the transformer should include the trademark, model and rated electrical parameters, or it should be accompanied by a label containing complete electrical parameters. The manual has clear wiring instructions.
3. Look at the parts list
In addition to good workmanship, a good-quality transformer is also inseparable from good materials, whether it is windings, insulating tape, The skeleton, core and leads (or pins) are all important. Insulating paint is often used in the production of transformers, which has a good effect on moisture-proof, heat dissipation, insulation and fixed windings of transformers. Some companies may not use insulating paint or use poor quality insulating paint, which will affect the performance and safety of the transformer and may even release toxic substances.
4. Check the certification certificate and test report
Transformer products are subject to CQC voluntary certification. If the transformer has a certification certificate, it can be verified online through the CQC website. Compared with products without certification certificates, transformers that have obtained certification certificates are more trustworthy.
Isolation transformers were used in the power industry in European countries in the early days. They are widely used in the electronic industry or industrial and mining enterprises, as control power supplies for general circuits in machine tools and mechanical equipment, and as power supplies for safety lighting and indicator lights. Isolation transformers are safety power supplies, generally used for machine repair and maintenance, and play a role in protection, lightning protection, and filtering.
If the website content violates your rights, please contact us to delete it。
