The principle and role of isolation transformer

First, what is an isolation transformer

Isolation transformer refers to the input winding and output winding with electrical isolation of the transformer, isolation transformer to avoid accidentally touching the charged body at the same time, the isolation of the transformer is to isolate the original and secondary winding coil of the respective current. Early for the European countries used in the power industry, widely used in the electronics industry or industrial and mining enterprises, machine tools and mechanical equipment in the general circuit control power supply, security lighting and indicator power.

The primary side, the secondary side of the winding between the higher insulation strength to isolate the different potential to inhibit common mode interference of the special transformer. The ratio of isolation transformer is usually 1:1.

Second, the principle of isolation transformer

The principle of isolation transformer and the principle of ordinary transformer is the same. Are using the principle of electromagnetic induction. Isolation transformer is usually a 1:1 transformer. As the secondary is not connected to ground. There is no potential difference between any one wire of the secondary and the ground. Safe to use. Commonly used as a maintenance power supply.

Isolation transformers are not all 1:1 transformers. Control transformers and tube equipment power supply is also an isolation transformer. Such as tube amplifier, tube radio and oscilloscope and lathe control transformer power supply are isolation transformer. For example, in order to safely repair the colour TV commonly used 1 to 1 isolation transformer. Isolation transformer is used more, in the air conditioning is also used.

General transformer original and secondary windings, although there is also the role of isolation circuit, but in the case of higher frequency, the capacitance between the two windings will still make the two sides of the circuit between the electrostatic interference. In order to avoid such interference, isolation transformer, the original and secondary windings are generally placed in different columns to reduce the capacitance between the two; also used the original and secondary windings placed concentrically, but in the windings between the addition of electrostatic shielding, in order to obtain a high level of anti-interference characteristics.

Electrostatic shielding is set between the original and secondary windings of a non-closed copper or non-magnetic conductive paper, known as the shielding layer. Copper or non-magnetic conductive paper with a wire connected to the shell. Sometimes in order to achieve better shielding effect, in the whole transformer, but also cover a shielding shell. The winding of the lead wire terminals are also shielded to prevent other external electromagnetic interference. This can make the original and secondary windings between the main only magnetic coupling, and the equivalent distribution capacitance between them can be less than 0.01pF, thus greatly reducing the original and secondary windings between the capacitance of the current, effectively inhibit the power supply as well as other circuits from a variety of interference.

Third, the role of the isolation transformer

1. So that the primary side and the secondary side of the electrical insulation, but also to make the circuit isolation. In addition, the use of its iron core of high-frequency loss characteristics, thereby inhibiting high-frequency clutter into the control loop. The use of isolation transformers to make the secondary to ground suspension, can only be used in the power supply range is smaller, shorter line occasions. At this time, the system's capacitive current to ground is not small enough to cause personal injury.

2. The role of electrical isolation, one is to protect the equipment, there is a very important role is to protect personal safety! Isolation of dangerous voltages. Isolation transformer output input capacitance coupling is small, due to lightning, discharge, grid switching, motor startup and other grid noise caused by interference more inhibitory effect, is more effective power supply noise suppressor.

From this point of view, the isolation transformer has a more protective role of the equipment. The so-called protection of personal safety, that is, the operation of this equipment is a protection. Because the electric potential of the isolation transformer is obtained through the secondary induction, and the primary side (and the earth to form a circuit) does not form a circuit, so it will not cause electric shock.

3. Change the voltage, such as 220V AC voltage into AC 15V, but there is a greater role is to separate the 220V GND and 15V GND, which is very important. As we know, when the human body holds the 220V zero wire in the hand and then contacts the earth, there is no current flow, while holding the fire wire in the hand and then contacting the earth, it will be life threatening.

Isolation transformer of this can isolate the reference point (i.e. ground) is very useful. After the isolation of the transformer, for example, is still 220V voltage, as long as to ensure that the two wires are not in contact with the earth, then the human body hand holding any one of them connected to the earth, there will be no problem.