The requirements and influences of special environmental conditions on motor insulation

During storage, transportation and use, motor products are often affected by harmful factors in the surrounding environment. Special environmental conditions for motors, based on the nature of the environmental factors, can be divided into two major categories: natural climate environments and industrial environments. Natural climate environments mainly include tropical, marine, cold, underground and plateau environments; industrial environments mainly include corrosive environments, explosive environments, high and low temperatures, high and low pressures, solid particles and dust, high-energy radiation and special mechanical loads, etc. 
There are two major types of special environmental factors: natural climate and industrial environment. Some of them act on the motor singly, while others act in combination (such as tropical outdoor places with corrosive and explosive hazards). Some act intermittently, while others act continuously. Moreover, the different sequences of the actions of various factors result in different impacts, thus forming a very complex situation. 
● Temperature Impact 
Due to the high ambient temperature affecting the motor's heat dissipation, its output power decreases. The strong effect of high temperature and ultraviolet rays accelerates the aging of insulating materials. In dry and hot areas, the relative humidity sometimes drops to 3%. High temperature and dryness cause insulating materials to become dry, wrinkled, deformed and cracked. High temperature is prone to cause the loss of potting compound. Low temperature makes rubber and plastic harden, become brittle and crack, and causes lubricating oil and coolant to freeze. 
●High humidity and moisture influence 
High relative humidity is prone to causing a water film to adhere to the surface. When the humidity exceeds 95%, water droplets often condense inside the motor, making metal parts prone to rust, lubricating grease deteriorate due to moisture, and some insulating materials expand when damp while others become soft and sticky. This leads to a deterioration in mechanical and electrical performance, increasing the likelihood of insulation breakdown and surface flashover. 
● Mold Impact 
In high-temperature and high-humidity environments, mold is most likely to grow. The secretions of mold can corrode metals and insulating materials, causing rapid aging of insulation and leading to short-circuit accidents. 
● Dust and sandstorms 
Dust (including industrial dust) refers to particles with diameters ranging from 1 to 150 micrometers; sand dust refers to quartz particles with diameters ranging from 10 to 1000 micrometers. When a lot of dust and sand dust deposit on the insulating surface, they will absorb moisture and cause a decline in electrical insulation performance. Conductive dust is even more likely to cause insulation leakage or short circuit accidents. 
Whether acidic or alkaline, corrosive dust is prone to deliquescence, thereby causing corrosion to metal parts and insulating components. When dust and sand enter the interior of the motor, it can lead to mechanical failures and component wear. If the amount is large, it will block the air ducts, affecting ventilation and heat dissipation. Therefore, for motors used in industrial dusty areas and outdoor sandy regions, sand and dust prevention measures must be taken. 
● Salt spray influence 
When the surging waves and waves in the ocean strike the rocky shores, the splashing water droplets become mist-like and enter the air. The suspended liquid particles of chlorides in the air are called salt spray. Salt spray forms an electrolyte on the surfaces of insulators and metals, accelerating the corrosion process and seriously affecting the insulation performance, such as causing corona discharge and increasing leakage current. 
● Hazards from Insects and Small Creatures 
In tropical regions, the damage caused by insects and small creatures is particularly severe. On the one hand, they build nests and leave corpses inside the motor, causing mechanical blockages; on the other hand, they bite through insulation or consume insulating materials, leading to short-circuit faults. Among them, termites, cockroaches, rats and snakes are the most harmful. 
● Corrosive gas 
In production sites of the chemical industry (including mines, fertilizers, medicines, rubber, etc.), there are mainly a large number of gases such as chlorine, hydrogen chloride, sulfur dioxide, nitrogen oxides, ammonia, hydrogen sulfide, etc. In dry air (with a maximum relative humidity of less than 70%), their corrosiveness is relatively small. However, in humid air, they will form acidic, alkaline and other corrosive mists. Generally, when the relative humidity of the air has not reached saturation and there is condensation on the surface of the product, the corrosion of metal parts and the deterioration of insulation performance will be greatly accelerated. Therefore, the degree of influence of corrosive gases on motor products depends on the air humidity and the nature and concentration of the corrosive gases. 
● Atmospheric pressure 
In high-altitude areas (above 1,000 meters), due to the decrease in air density with the increase in altitude, the temperature rise of the motor increases and its output power decreases. The corona onset voltage of high-voltage motors will also decrease accordingly. If the motor operates with corona for a long time, it will affect the service life and safe operation of the motor. 
In addition, altitude changes have a significant impact on DC commutation and brush wear. Under atmospheric conditions lacking moisture and oxygen (especially moisture), the formation rate of the cuprous oxide film on the commutation surface slows down and cannot balance with the wear, thus leading to commutation deterioration and an increase in brush wear. 
●High-energy rays 
High-energy rays (such as electrons, protons or gamma rays from nuclear radiation) can cause atomic displacement in materials, generating lattice defects and forming vacancy-interstitial atom pairs, thereby causing radiation damage to the material structure. Additionally, radiation can cause electrons to be stripped from their orbits, creating hole-electron pairs, which can easily lead to material ionization. The impact of radiation on insulating materials depends on the type and dose of radiation (indicated by dose rate or cumulative dose value), the energy spectrum of the radiation, the properties of the insulating material being irradiated, and the ambient temperature. 
Radiation mainly causes damage to insulating materials, with more severe mechanical property damage to organic insulating materials. The allowable absorbed radiation dose for organic insulating materials is 10° rad, while inorganic insulating materials have better radiation resistance. For instance, the allowable absorbed radiation dose for quartz and mica can reach over 10° rad. 
● Mechanical force 
High pressure, impact and vibration loads can easily cause mechanical damage to the metal components and insulation structure of the motor.