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Special environmental conditions and their effects on motor insulation
- Jan 11, 2019 -

Special environmental conditions and their effects on motor insulation

In the basic motor knowledge training, the very careful staff L asked how different special working conditions affect the motor performance. Ms. Participation today on the issue of small L, the basic conditions of the storage and use of the motor are basically summarized, and the relationship between special conditions and motor performance is shared with you.

Motor products are often affected by harmful factors in the surrounding environment during storage, transportation and use. The special environmental conditions of the motor can be divided into two categories: natural climate environment and industrial environment according to the nature of environmental factors. The natural climatic environment mainly includes tropical, marine, cold, underground and highland environments; the industrial environment mainly includes corrosive environment, explosive environment, high and low temperature, high and low pressure, solid particles and dust, high energy ray and special mechanical load.

The influence of special environment on motor insulation

There are two special types of environmental factors, natural climatic environment and industrial environment, some of which are solely for the motor, and some of which are combined with several factors (such as places with corrosive and explosive hazards in the tropical environment); some are intermittent, some are continuous The role, combined with the different priorities of the various factors, has different effects, thus forming a very complicated situation.

● Temperature effect

Since the high ambient temperature affects the heat dissipation of the motor, the output is reduced. The high temperature and ultraviolet light are strong, which accelerates the aging of the insulating material. The relative humidity in the dry and hot areas is sometimes reduced to 3%. The high temperature drying causes the insulation to dry, shrink, deform and crack. High temperature is easy to lose glue. Low temperatures cause hardening of rubber and plastics, cracking of tubes, freezing of grease and coolant.

●High humidity and moisture effects

The relative humidity is high, so that the surface is condensed with water film. When the humidity is higher than 95%, the inside of the motor often condenses water droplets, which makes the metal parts easy to rust, the grease is deteriorated by moisture, some of the insulating materials are damp and some are soft and sticky. Mechanical and electrical properties deteriorate, and insulation breakdown and surface flashover are prone to occur.

●Mold effect

In high temperature and high humidity environment, mold is the most prone to growth, and the secretion of mold can corrode metal and insulating materials, causing the insulation to age rapidly and cause short circuit accidents.

●dust and dust

Dust (including industrial dust) refers to particles in the range of 1 to 150 microns in diameter; sand dust refers to quartz particles in the range of 10 to 1000 microns in diameter. When dust and dust are deposited on the insulating surface, the electrical insulation performance is degraded due to moisture absorption, and the conductive dust is more likely to cause insulation leakage or short circuit accident.

Corrosive dust, whether acidic or alkaline, is easily deliquescent, causing corrosion of metal parts and insulation. When dust and dust enter the inside of the motor, it will cause mechanical failure and component wear. If the amount is too much, the air passage will be blocked, which will affect the ventilation and heat dissipation. Therefore, dust-proof measures must be taken for motors used in industrial dusty areas and outdoor dust areas.

●Salt fog effect

When the waves and waves in the ocean impact the rocky shore, the flying water droplets become foggy and enter the air, so that the chloride liquid particles suspended in the air are called salt spray. The salt spray causes the electrolyte and the metal surface to form an electrolyte, accelerates the corrosion, and seriously affects the insulation performance, such as generating corona discharge and increasing the leakage current.

●Insects and small creatures

Insects and small organisms are particularly harmful in the tropics. One side and the inside of the motor do the nest and the remains of the body, causing mechanical obstruction; on the other hand, biting the insulation or ingesting the insulating material, causing a short circuit failure. In particular, termites, flying piers, rats, and snakes are the most harmful.

●Corrosive gas

In the chemical industry (including mines, fertilizers, medicines, rubber, etc.) production sites, there are mainly chlorine, hydrogen chloride, sulfur dioxide, nitrogen oxides, ammonia, hydrogen sulfide and other gases, which are in dry air (the maximum relative mixing is lower than 70% of the environment), although the corrosion is small, in the humid air, acidic, alkaline and other corrosive aerosols are formed. Generally, corrosive gases will greatly accelerate the deterioration of metal zero, component corrosion and insulation performance when the relative humidity of the air is not saturated and condensation is present on the surface of the product. Therefore, the degree of influence of corrosive gases on motor products depends on the nature of air humidity and corrosive gases and their concentrations.

●Atmospheric pressure

In the plateau area (above 1000 meters), the air density decreases as the sea level rises, which affects the increase in motor temperature rise and output. The corona starting voltage of the high-voltage motor will also decrease accordingly. If the motor is operated with a long-term corona, it will affect the service life and safe operation of the motor.

In addition, the change of sea level has a great influence on DC commutation and brush wear. In the absence of moisture and oxygen (especially moisture), the formation of the cuprous oxide film on the commutating surface slows down and cannot be balanced with wear. Therefore, the commutation deteriorates and the amount of brush wear increases.

●High energy ray

High-energy rays (such as electrons, protons, or gamma rays from nuclear radiation) can displace atoms in a substance, create lattice defects, form vacancy-gap atom pairs, and cause the structure of the material to be damaged by radiation. In addition, after the substance is irradiated, the electrons are de-orbited, and a hole-electron pair is generated, which is easy to ionize the substance. The effect of radiation on the insulating material depends on the type and dose of radiation (expressed in dose rate or cumulative dose value), the energy spectrum of the radiation, the nature of the insulating material being irradiated, and the ambient temperature.

Radiation is mainly caused by damage to the insulating material. The mechanical properties of the organic insulating material are seriously damaged. Its allowable radiation dose is 10° rad, while the inorganic insulating material has good radiation resistance, such as quartz, mica. The radiation dose can reach above 10° rad.

●Mechanical force

High air pressure, shock and vibration loads can easily cause mechanical damage to metal parts and insulation structures of motors.

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