The fan generates excessive heat when operating at low frequencies
Thread Content
This post was last edited by *eyang on 2010-1-4 14:10. I work in the manufacturing field and have no knowledge of electrical systems. The fans in our factory operate at a low frequency of 18 Hz for extended periods of time, which causes the motors of these fans to overheat severely; in some cases, the motors even get damaged. What are the reasons and mechanisms behind the increased heating at this low frequency compared to operating at normal frequency, and what are the solutions? Thank you. The fan is a standard centrifugal fan, and the frequency converter is from Mitsubishi.
I won’t go into detail about the reasons for this overheating; the solution is to install a fan that provides cooling at line frequency on the motor.
2# Air Force: Is a fan motor specifically added to the motor for cooling?
We want to buy a dedicated variable-frequency fan so that the cooling effect isn’t affected by a reduction in frequency. The effect is still unknown.
It is normal for low frequencies to generate a large amount of heat, and the main reason for this is that the excitation current of the motor accounts for too high a proportion of the total stator current! In other words, your supplier or engineer does not understand the characteristics of speed control for fans and pumps: the speed control range is only 30%, meaning the speed frequency cannot be lower than 30HZ; otherwise, the effective operating point of the entire fan system will move outside its optimal operating range!
It is recommended to adjust the fan’s frequency to the medium-to-high frequency range
Well, set the lower frequency limit for the inverter, and also configure the electronic thermal protection. This minimum frequency should meet the operating requirements of the fan.
The motor overheats due to insufficient cooling conditions; a cooling fan is needed
Haha, I saw that so many solutions were mentioned above, but they’re all not feasible. The speed of the motor is determined by the process conditions, so it’s not possible to focus on restricting its speed. Many people suggest adding an industrial-frequency wind turbine, but this is also very difficult to implement – is the machinery suitable for this purpose? And where should it be installed? Right, I recommend that you purchase motors designed for variable frequency use, as such motors have two advantages: first, the cooling fan is not located on the shaft but is powered separately at the standard frequency, so its performance isn’t reduced due to a decrease in the motor’s speed, which ensures effective cooling ； Second, the magnetic circuit design of variable-frequency motors also takes into account operation at low frequencies over extended periods of time; in terms of insulation and other aspects, such motors are superior to ordinary motors.
Adding a cooling AC fan will do.
Ordinary motors cannot operate for long periods at low frequencies; if necessary, it is better to use an inverter-driven motor.