In order to adapt to different operating environments, the motors are manufactured with different protection levels. The more common ones are IP22, IP23 and other protective structures and IP44, IP54 and other closed structures, while the closed structure motors of IP44 and higher protection levels have two sets of internal circulation and external circulation structures for ventilation and heat dissipation, and most of the motors are on the shaft With external fans, motors with different numbers of poles and different energy efficiency levels, the size of the fan and the shape of the wind cover are quite different.
For variable frequency motors, there are protective structure motors with volute-type centrifugal fans and enclosed structures with axial fans, and there are also cases without special fans, such as some short-time work systems or occasions where the normal speed is not lower than the specified speed. But most of the motors used for continuous frequency conversion are generally matched with independent fans dedicated to ventilation and heat dissipation, that is, the fans work independently of the motor, and use a special power supply and control system to ensure the speed of the fan impeller under different frequency bands. No change, the ventilation and heat dissipation conditions of the motor remain unchanged. Because the variable frequency motor allows broadband operation, any frequency band, especially for low frequency bands, the heating of the motor is basically unchanged, and when the motor speed is low, the air volume of the built-in fan structure when the motor speed is low is not enough to meet the motor's heat dissipation requirements.
The reason why frequency conversion motors are favored by customers is their energy-saving advantages under variable speed conditions. In most cases, the load or speed required for equipment operation is high or low, and the power saving effect of low-power operation at low speed is very significant. Most of the time it runs at full load or at full speed, and the inverter is only used as a soft start device, so there is almost no power saving effect.
In some actual use process, some customers use frequency converter to supply power and run the ordinary motor. If it only meets the starting control, there will be no problem. However, if the industrial frequency motor is operated as a variable frequency motor, it will cause the motor to run at a low speed. The winding was severely heated and burned. From the appearance of motor failure, it is similar to overload, but the root cause is that the heat dissipation condition of the motor does not meet the requirements; for the same reason, when the variable frequency motor is working, the fan must be in normal working condition, otherwise it will cause the heating problem of the motor winding. .