Safety requirements for isolation transformers

Requirements for using isolated safety transformers:

1. The isolation transformer is a safe power source, which is generally used for maintenance, lightning protection and filtering of machine maintenance. The isolation transformer is a 1/1 transformer. Primary single phase 220V, secondary is also single phase 220V. Or the primary three-phase 380V, the secondary is also three-phase 380V. First of all, the AC power supply voltage we usually use is connected to the ground by a line, and the other line has a potential difference of 220V from the earth. Human contact can cause electric shock. The secondary of the isolation transformer is not connected to the earth, and there is no potential difference between any two lines and the earth. It is safer for people to touch any line without electric shock. Secondly, the output of the isolation transformer is completely isolated from the input, which effectively filters the input of the transformer (the supply voltage supplied by the grid). This provides a clean supply voltage to the consumer.

2. The electrical insulation of the primary side and the secondary side of the safety isolating transformer is completely insulated, and the circuit is also isolated. In addition, the high frequency loss of the core is utilized to suppress high frequency clutter from being transmitted to the control loop. The isolation transformer is used to suspend the second ground to the ground, and can only be used in the case where the power supply range is small and the line is short. At this point, the system's capacitance to ground capacitance is not small enough to cause personal injury.

3. Safety isolation transformers are not all power transformers. The power supply that controls the transformer and tube equipment is also an isolation transformer. Power supplies such as tube amplifiers, tube radios, and oscilloscopes and lathe control transformers are isolation transformers. For example, a 1 to 1 isolation transformer is commonly used for safe maintenance of color TV sets. Isolation transformers are used more and are also used in air conditioners.

4. Although the original transformer and the secondary winding have the function of an isolation circuit, the capacitance between the two windings still causes static interference between the two circuits at a high frequency. In order to avoid such interference, the primary and secondary windings of the isolation transformer are generally placed on different cores to reduce the capacitance between the two; the original and the secondary windings are concentrically placed, but are placed between the windings. Electrostatic shielding for high anti-interference characteristics.

5, safety isolation transformer electrostatic shielding is to set a piece of copper or non-magnetic conductive paper between the original and secondary windings, called the shielding layer. Copper or non-magnetic conductive paper is connected to the outer casing with wires. Sometimes in order to achieve a better shielding effect, the entire transformer is also covered with a shielded casing. The lead terminal of the winding is also shielded to prevent other external electromagnetic interference. In this way, only the magnetic coupling between the primary and secondary windings is mainly left, and the equivalent distributed capacitance between them can be less than 0.01 pF, thereby greatly reducing the capacitance current between the primary and secondary windings, and effectively suppressing the power supply and other circuits. Various interferences.