The operation process of the motor is actually a process of mutual conversion between electrical energy and mechanical energy, and some losses will inevitably occur during this process. The vast majority of these losses are converted into heat, which increases the operating temperature of the motor windings, iron core, and other components.
Motor heating problems are common in the process of R&D and production of new products. Ms. Shen has also been exposed to many cases where the motor temperature rises in steps and it is difficult to stabilize the temperature rise during the type test. Combined with this question, Ms. participated briefly today to talk about the cooling method and ventilation and heat dissipation of the motor, analyze the ventilation and cooling structure of various motors, and try to discover some design techniques to avoid the motor overheating.
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 cooling is commonly used for fully enclosed air cooling and open air cooling; water cooling is common with 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 + push method code
1. Common cooling methods
1. 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 for 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.
4. Water cooling
The heat generated by the large losses in the motor is dissipated through the surface of the motor into the surrounding air. 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 filled with water in the hottest part of the motor, and the circulating air inside the motor will give the inner heat to the quilt. Water cooled surface.
5. Hydrogen cooling
In high-speed electrical machines, such as turbo-generators, hydrogen cooling is used. 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 cooling
In some motors, the stationary parts, and even the rotating parts, are cooled by 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.
Post time: May-25-2023
