The influence of altitude and ambient temperature on motor selection

Environmental factors of the motor

       a) Altitude. Generally selected motors are all applicable when the altitude does not exceed 1000m. When the motor operating location is in the range of 1000m to 4000m, as the altitude increases, the air density decreases, the motor heat dissipation is poor, and the winding temperature rises. However, the ambient air temperature decreases by 0.5°C to 0.65°C for every 100m increase in altitude, which compensates Insufficiency of poor winding cooling effect. At this time, the temperature rise value specified by the motor does not need to be corrected. When the motor operating location is above 4000m above sea level, the temperature rise value of the motor should be determined through negotiation between the user and the manufacturer.

      b) Ambient temperature. When the temperature around the motor is too low, the motor insulation material becomes brittle, the bearing grease freezes, and the starting capacitor fails due to the freezing of the electrolyte. When the temperature is too high, the actual temperature of the winding will increase (actual temperature = ambient temperature + temperature rise), and overheating will have a bad effect on the insulation. Therefore, it is stipulated that when the surrounding temperature of the motor operating location is often lower than 0℃, the winding temperature rise correction value and motor performance index should be negotiated and determined by the user and the manufacturer; when the operating location temperature is 0-40℃, the temperature rise limit is generally Without correction, when the highest temperature at the place of use is 40~60℃, the actual temperature rise limit should be the temperature rise value specified in the standard minus the difference of the part where the ambient temperature exceeds 40℃. When the temperature of the place of use exceeds 60°C, the temperature rise limit should be negotiated and determined by the user and the manufacturer.

      c) Environmental humidity. The insulation resistance of the motor decreases as the humidity increases. Under general environmental humidity conditions, E-class or B-class insulation class motors can be selected, but for occasions with high environmental humidity, it is best to choose a motor with high insulation class (such as F class). Or you can choose a dedicated motor.

      d) When the environment around the motor is filled with harmful substances, if these substances enter the motor, it will cause great harm. For example, in petroleum and chemical plants that use explosive gases such as gasoline and propane, and in coal mines with coal dust and methane gas, explosion-proof motors must be selected; in the occasions where there are strong corrosive acid-base gases and liquids that corrode the motors, Anti-corrosion motors must be used; when water droplets and sundries may invade the inside of the motor, it is necessary to choose drip-proof, drip-proof, and fully enclosed fan-cooled motors according to different conditions.