Understanding of safety isolation transformer

The Transformer with primary and secondary windings separated can be called barrier transformer, because the primary and secondary windings are now completely separated (barrier), and energy is transferred through the magnetic field. The effect of blocking transformer is to use electricity safely, but after blocking, it does not mean that it is definitely safe, because the output voltage of the barrier transformer with the transformation ratio of 1:1 (or smaller) may be higher than 36V. When touching two wires together, there will still be current flowing through the human body, causing the risk of electric shock. So even the safety barrier transformer can not touch two wires together!

1： Why use barrier transformer?

First of all, we should first understand the power supply system in China. When supplying low-voltage users, China's power supply system generally adopts the three-phase four wire system. The neutral line grounding is the wire to the residents' home. One is the phase line (front), and the other is the zero line. It is in the same position with the earth. When the human body touches the thermal bottom plate, it will make the current pass through the human body and form a loop with the earth, forming an electric shock damage. If the use of barrier transformer, it will be safer, because the primary and secondary is through the magnetic field exchange energy, there is no physical hard connection, even if the human body touches the charged object, it will also be because the human body and the earth are in the same position, and the potential of the charged part will be low potential, which will not cause electric shock damage.

2： There are two main benefits of using barrier transformers,

1. Safety! The zero line of communication power (220 V single phase) is connected with the earth, and there is a communication voltage of 220 V between the front and the earth. People standing on the ground, so with the zero line equipotential, if people touch the front, will be electrocuted. The secondary of the barrier transformer is not connected with the earth, and its output is "floating". When a person touches any line of the secondary of the barrier transformer, because it can not form a current loop, it will not get electric shock, so it is relatively safe. The same is true for the three-phase four wire power line. However, it should be noted that if the two secondary lines are touched together, they will be electrocuted. Therefore, the barrier transformer can not ensure the safety, or to always abide by the safety norms.

2. Prevent power electronic devices from polluting the power grid. Transformer has great attenuation effect on high frequency harmonics, so it can prevent power electronic equipment from polluting the power grid. Of course, the reverse is also true. The noise of the power grid will be blocked by the barrier transformer to prevent the interference to the secondary side electrical equipment. With the continuous development of the power system, the transformer as a key equipment in the power system plays an increasingly important role, its safe operation is directly related to the reliable operation of the entire power system.