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HCPL-2602#500: the special purpose of isolators

PostPosted: Fri Mar 03, 2017 2:48 am
by maryzhu
I bought an isolator couple days ago, just like this: HCPL-2602#500, then I read a magazine called semiconductor news. I carefully read it and found I was interested in isolators. Thus I searched many materials about isolators, but they're not specific at all. So I come to this forum to turn to you to get your ideas about the special purpose of isolators.


My understanding is that things that are not good at conducting current are called insulators, and insulators are also known as dielectrics. Their resistivity is extremely high. Insulator definition: not easy to conductive objects called insulators. Insulators and conductors, there is no absolute limit. The insulator can be converted into conductors under certain conditions. Here to note: the reasons for the conductive: whether solid or liquid, if there is free to move the internal electrons or ions, then he can be conductive. There is no free movement of the charge, under certain conditions, can produce conductive particles, then it can also be a conductor.

Satisfied answer Insulator, also known as dielectric, is a material that hinders the flow of charge. In insulators, valence electrons are tightly bound around their atoms. This material is used as an insulator in electrical equipment or as an insulating effect. Its role is to support or separate the various electrical conductors, so that no current flow. An insulator is a substance that does not conduct current in the usual case.

Insulators in some external conditions, such as heating, high pressure and other effects, will be "breakdown", and into a conductor. The insulator is not an absolutely non-conductive object before it is broken. If a voltage is applied across the insulating material, a weak current will appear in the material.
Insulating material usually only a small amount of free electrons, before the breakdown is not involved in the conductive charged particles mainly by the thermal movement and dissociation of the intrinsic ion and impurity particles. The electrical properties of the insulator are reflected in the process of conductance, polarization, loss and breakdown.

Insulator Conductive

Insulators are substances that do not have conductivity. The electron band theory states that the electrons in the solid are only allowed to exist in a certain energy state, which forms an energy band that separates from each other. Electrons tend to occupy the lowest energy band, the absolute energy can be filled in the absolute zero can be called the price band, the price band above the band called the conduction band, the price band and the gap between the conduction band is called Gap. Above absolute zero, the valence band electrons are excited to jump to the conduction band, become conduction band electrons, and leave holes in the valence band. According to the band theory, electrons are filled with energy band or empty energy band does not contribute to the conductance, conductance only from half full of energy band, conduction band electrons and valence band hole collectively. The metal conduction band is partially filled and thus has a good conductance. For semiconductors and insulators, the valence band is filled at zero, and the conduction band does not have electrons. At room temperature, the semiconductor due to the smaller energy gap, can be formed by thermal excitation of electron hole pairs, which has a certain conductance. In contrast, the vast majority of insulators typically have a very large bandgap width, and valence electrons are hard to be excited to the conduction band, so the insulator has a very low carrier concentration, and the conductivity is also very low, or the material is insulated.

For insulators, there is always a breakdown voltage, which gives the valence electron energy enough to excite the conduction band. Once the breakdown voltage is exceeded, the material is no longer insulated. However, the breakdown is usually accompanied by a physical or chemical change that destroys the insulation of the material.

The above discussion deals only with electron conduction. In addition to the absence of electron conduction, the insulator can not have other moving charge to bring the conductivity. For example, if ions are present in the liquid or gas, the ions can move to form a current, so that the material is a conductor. The electrolyte or plasma is a conductor, with or without the presence of electrons.

Insulator breakdown

Insulators are affected by electrical breakdown. When the applied electric field exceeds a certain threshold (this threshold is proportional to the energy gap width of the material), the insulator will suddenly turn into a conductor and may have catastrophic consequences. In the process of electric breakdown, free electrons are accelerated by a strong electric field to a sufficiently high velocity, and these high-speed electrons strike the electrons and bind the electrons from the restraint (ionization) of the bound electrons. The new free electrons can be accelerated and hit other atoms, producing more free electrons, forming a chain reaction. Soon the insulator will be filled with moving carriers, so its resistance will drop to a very low level. In the air, the corona discharge is a normal current near the high voltage conductor; the arc discharge is abnormal and does not want to see the current. Similarly, the breakdown can occur in any insulator, even in solids. There is even some form of breakdown of the vacuum, but this breakdown or vacuum arc is related to the electron emission of the electrode surface, rather than by the vacuum itself.

Those are just my understandings. What is your idea ? Any of your ideas would be highly appreciated.

May someone would like to help me ?

thanks in advance.