Define corona discharge. Corona discharge : definition of Corona discharge and synonyms of Corona discharge (English)

Corona discharge

define corona discharge

The inner region is an ionizing plasma, the middle a non-ionizing plasma. Examples Corona discharge may be seen around wires that have become worn. The total number of electrons, and electron density is much greater than in the corresponding positive corona. Positive coronas Properties A positive corona is manifested as a uniform plasma across the length of a conductor. The discharge will occur when the strength of the around the conductor is high enough to form a conductive region, but not high enough to cause or to nearby objects. A positive corona generates much less ozone than the corresponding negative corona, as the reactions which produce ozone are relatively low-energy.

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Corona discharges

define corona discharge

However, the electrons in a positive corona are concentrated close to the surface of the curved conductor, in a region of high potential gradient and therefore the electrons have a high energy , whereas in a negative corona many of the electrons are in the outer, lower-field areas. Spontaneous corona discharges are undesirable where they waste power in high-voltage systems or where the high chemical activity in a corona discharge creates objectionable or hazardous compounds, such as ozone. A further feature of the structure of negative coronas is that as the electrons drift outwards, they encounter neutral molecules and, with such as and , combine to produce negative ions. It is often seen as a bluish or other color glow in the air adjacent to pointed metal conductors carrying high voltages. The outer region is known as the unipolar region.

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What does corona discharge mean?

define corona discharge

It appears a little larger than the corresponding positive corona, as electrons are allowed to drift out of the ionising region, and so the plasma continues some distance beyond it. Therefore, whilst for many reactions the increased electron density will increase the reaction rate, the lower energy of the electrons will mean that reactions which require a higher electron energy may take place at a lower rate. Beyond the plasma, in the unipolar region, the flow is of low-energy positive ions toward the flat electrode. It often appears as tufts of corona at sharp edges, the number of tufts altering with the strength of the field. Outside this the ions move through the air without creating new ions. The inner two regions are known as the corona plasma. The free radicals and ions generated in corona reactions can be used to scrub the air of certain noxious products, through chemical reactions, and can be used to produce.

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What does corona discharge mean?

define corona discharge

As with positive coronas, the establishing of a corona begins with an exogenous ionization event generating a primary electron, followed by an electron avalanche. Therefore, if electrons are to be used in an application which requires a high activation energy, positive coronas may support a greater reaction constants than corresponding negative coronas; though the total number of electrons may be lower, the number of a very high energy electrons may be higher. Problems caused by corona discharges Coronas can generate audible and radio-frequency noise, particularly near lines. The physics of positive and negative coronas are strikingly different. In a positive corona all the electrons are attracted inward toward the nearby positive electrode and the ions are repelled outwards. Corona discharge usually forms at highly curved regions on electrodes, such as sharp corners, projecting points, edges of metal surfaces, or small diameter wires. In a positive corona, secondary electrons, for further avalanches, are generated predominantly in the fluid itself, in the region outside the or avalanche region.

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Corona discharge : definition of Corona discharge and synonyms of Corona discharge (English)

define corona discharge

However, they are of a predominantly lower energy, owing to being in a region of lower potential-gradient. The inner region is known as the plasma region, the outer as the unipolar region. The uniformity of the plasma owes itself to the homogeneous source of secondary avalanche electrons described in , below. Air near the electrode can become ionized partially conductive , while regions more distant do not. Only a small number of gas molecules take part in the electron avalanches and are ionized, having energies close to the ionization energy of 1 - 3 ev, the rest of the surrounding gas is close to ambient temperature. Coronas are efficient producers of ozone in air. Again, the source of energy for the electron-liberation is a high-energy photon from an atom within the plasma body relaxing after excitation from an earlier collision.

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Corona discharge

define corona discharge

This is determined by the polarity of the voltage on the highly-curved electrode. See below for more details. If the curved electrode is positive with respect to the flat electrode we say we have a , if negative we say we have a. The electrons resulting from the ionisation of a neutral gas molecule are then electrically attracted back toward the curved electrode, attracted into the plasma, and so begins the process of creating further avalanches inside the plasma. If the geometry and gradient are such that the ionized region continues to grow until it reaches another conductor at a lower potential, a low resistance conductive path between the two will be formed, resulting in an.

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