During the use of the motor, due to the existence of loss, the temperature continues to rise. If it is not well cooled, the service life of the motor will be affected. The power of high-voltage motors is generally large, and the value of power loss is also large. For normal use, cooling is particularly important.For open-type motors, ambient air is generally used to directly enter the motor for cooling, and the cold air directly takes away the heat of the motor and discharges it to the surrounding environment. There are three main routes for the air to travel inside the high-voltage motor. One is axial, cold air enters from one end of the motor and exhausts from the other end. Because only one end of the fan is installed, a larger diameter fan can be installed, the cooling is better, and the iron core structure is more compact. The disadvantage is that the ventilation loss is large, and the temperature distribution along the axial direction of the motor is not uniform. It is generally used for motors with small capacity.The other is radial, where cold air enters from both ends and is discharged from the radial air passages of the iron core. The disadvantage is that the fan must be installed at both ends, so the outer diameter of the fan can only be smaller than the diameter of the rotor. The fan capacity is limited and radial ventilation slots are required, making the motor slightly larger. The advantage is that due to the use of axial flow fans, the ventilation efficiency is high, the heat dissipation area is large, and the temperature along the axial direction of the high-voltage motor is more uniform. There is also axial and radial composite ventilation, which is designed by combining the advantages of axial and radial ventilation. It has better ventilation and cooling, and the temperature is more uniform, but the structure is more complex. Since the insulating material used in the motor has a temperature limit, the task of cooling the motor is to dissipate the heat generated by the internal loss of the motor, so that the temperature rise of each part of the motor is maintained within the range specified by the standard, and the internal temperature should be uniformized. .
The motor usually uses gas or liquid as the cooling medium, and the common ones are air and water, which we call air cooling or water cooling. Air-cooled common ones include fully enclosed air cooling and open air cooling; water-cooled common ones include water jacket cooling and heat exchanger cooling.
The AC motor standard IEC60034-6 specifies and explains the cooling method of the motor, which is represented by the IC code:Cooling method code = IC + circuit arrangement code + cooling medium code + driving method code
1. Common cooling methods1. IC01 natural cooling (surface cooling)For example Siemens compact 1FK7/1FT7 servo motors. Note: The surface temperature of this type of motor is high, which may affect the surrounding equipment and materials. Therefore, in some industrial applications, consideration should be given to avoiding the negative impact of motor temperature through motor installation and moderate derating.2. IC411 self-fan cooling (self-cooling)IC411 realizes cooling by moving the air through the rotation of the motor itself, and the moving speed of the air is related to the speed of the motor.3. IC416 forced fan cooling (forced cooling or independent fan cooling)IC416 contains an independently driven fan, which ensures a constant air volume regardless of the speed of the motor.IC411 and IC416 are the cooling methods often used in low-voltage AC asynchronous motors, and the heat dissipation is achieved by blowing the cooling ribs on the surface of the motor by a fan.1. The type of cooling fan of the motor2. Backward centrifugal fan3. Radial centrifugal fan4. Axial flow (propeller type)The design of the fan is based on the principle of obtaining the maximum cooling effect with the minimum loss, and the streamlined surface design is mostly used to maximize the ventilation efficiency of the fan and reduce the ventilation noise.4. Water coolingThe heat generated by the large losses in the motor is dissipated into the surrounding air through the surface of the motor. When the motor is working under certain conditions, in order to prevent the high temperature rise of various parts of the motor, sometimes there are special channels or pipes with water in the hottest part of the motor. Water cooled surface. 5. Hydrogen coolingHydrogen cooling is used in high-speed electrical machines such as turbo-generators. In a closed system, the hydrogen gas several percent higher than the atmospheric pressure is circulated internally by the built-in fan, and then flows through the heat-generating part of the motor and the water-cooled tube cooler in turn. 6. Oil coolingIn some motors, the stationary parts, and even the rotating parts, are cooled with oil, which circulates inside the motor and through coolers placed outside the motor. 2. Motor classification based on cooling method(1) The natural cooling motor does not use special methods to cool the various parts of the motor, and only relies on the rotation of the rotor itself to drive the air.(2) The heating part of the self-ventilated motor is cooled by a built-in fan or a special device attached to the rotating part of the motor.(3) Externally ventilated motor (blow-cooled motor) The outer surface of the motor is cooled by the wind generated by the fan mounted on the motor shaft, and the outside air cannot enter the heating part inside the motor.(4) The circulation of the motor cooling medium with additional cooling equipment is generated by special devices outside the motor, such as water cooling cabinets, air cooling cabinets and centrifugal eddy current fans.
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