During storage, transportation, and use, electric motors are frequently affected by harmful environmental factors. The specific environmental conditions of electric motors can be broadly categorized into two types based on the nature of the environmental factors: natural climatic environments and industrial environments. Natural climatic environments mainly include tropical, marine, cold, underground, and plateau environments.
During storage, transportation, and use, electric motors are frequently affected by harmful environmental factors. The specific environmental conditions of electric motors can be broadly categorized into two types based on the nature of the environmental factors: natural climatic environments and industrial environments. Natural climatic 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.
The Influence of Special Environments on Motor Insulation
There are two main categories of special environmental factors: natural climate and industrial environment. Some factors act on motors in a single way, while others act in combination (such as in tropical outdoor locations with corrosive and explosive hazards). Some factors act intermittently, while others act continuously. In addition, the different sequences of action of various factors result in different effects, thus creating a very complex situation.
● Temperature effect
High ambient temperatures affect motor heat dissipation, reducing output. High temperatures and strong ultraviolet radiation accelerate the aging of insulation materials. In hot, dry regions, relative humidity can sometimes drop to 3%, causing insulation to dry out, shrink, deform, and crack. High temperatures also cause adhesive loss. Low temperatures harden rubber and plastics, make pipes brittle and crack, and cause lubricating grease and coolant to freeze.
●The effects of high humidity and moisture
High relative humidity easily causes water film to condense on the surface. When the humidity is above 95%, water droplets often condense inside the motor, making metal parts prone to corrosion, lubricating grease deteriorating due to moisture, and insulation materials sometimes swelling when damp, sometimes becoming soft and sticky. This deteriorates the mechanical and electrical properties and makes insulation breakdown and surface flashover more likely.
●Mold effects
In environments with high temperature and high humidity, mold thrives. Mold secretions can corrode metals and insulation materials, causing insulation to age rapidly and leading to short circuits.
●Dust and sand
Dust (including industrial dust) refers to particles with a diameter ranging from 1 to 150 micrometers; sand and dust refer to quartz particles with a diameter ranging from 10 to 1000 micrometers. When dust and sand accumulate on insulating surfaces, they can absorb moisture, which can reduce the electrical insulation performance. Conductive dust is more likely to cause insulation leakage or short circuit accidents.
Corrosive dust, whether acidic or alkaline, is hygroscopic, causing corrosion to metal parts and insulation. When dust and sand enter the motor, they can cause mechanical failures and wear on components. Excessive amounts can also clog air ducts, hindering ventilation and heat dissipation. Therefore, motors used in dusty industrial areas and outdoor dusty regions must be protected against dust.
●Impact of salt spray
When ocean waves crash against rocky shores, they cause spray to become mist and enter the air. These suspended chloride liquid particles are called salt spray. Salt spray causes electrolytes to form on insulating and metal surfaces, accelerating corrosion and severely affecting insulation performance, such as causing corona discharge and increased leakage current.
●Harm caused by insects and small organisms
In tropical regions, the damage caused by insects and small creatures is particularly severe. On the one hand, they nest inside motors and leave their dead bodies, causing mechanical blockages; on the other hand, they bite or ingest insulation materials, causing short circuits. Termites, ground beetles, rats, and snakes are especially harmful.
●Corrosive gases
In chemical industrial production sites (including mines, fertilizers, pharmaceuticals, rubber, etc.), there are often significant amounts of gases such as chlorine, hydrogen chloride, sulfur dioxide, nitrogen oxides, ammonia, and hydrogen sulfide. While these gases exhibit minimal corrosiveness in dry air (with a maximum relative humidity below 70%), they can form acidic or alkaline corrosive mists in humid air. Typically, when the relative humidity of the air is not saturated and condensation exists on the product surface, corrosive gases significantly accelerate the corrosion of metal components and the deterioration of their insulation performance. Therefore, the impact 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 1000 meters), the air density decreases with altitude, leading to increased motor temperature rise and reduced output. The corona initiation voltage of high-voltage motors will also decrease accordingly. If the motor operates with corona discharge for extended periods, it will affect the motor's lifespan and safe operation.
In addition, changes in altitude have a significant impact on DC commutation and brush wear. Under atmospheric conditions lacking moisture and oxygen (especially moisture), the formation rate of cuprous oxide film on the commutation surface slows down and cannot be balanced with wear, thus leading to commutation deterioration and increased brush wear.
●High-energy rays
High-energy radiation (such as electrons, protons, or gamma rays from nuclear radiation) can cause atomic displacement in matter, creating lattice defects and forming vacancy-interstitial atomic pairs, thus damaging the material's structure. Additionally, radiation can cause electrons to deorbit, creating electron-hole pairs, which can easily ionize the material. The effects of radiation on insulating materials depend on the type and dose of radiation (expressed as dose rate or cumulative dose value), the energy spectrum of the radiation, the properties of the irradiated insulating material, and the ambient temperature.
Radiation primarily damages insulating materials, with organic insulating materials suffering more severe mechanical damage. Their permissible absorbed radiation dose is 10 rad, while inorganic insulating materials have better radiation resistance. For example, the permissible absorbed radiation dose of quartz and mica can reach more than 10 rad.
●Mechanical force
High air pressure, impact and vibration loads can easily cause mechanical damage to the metal parts and insulation structure of the motor.
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