Views: 6 Author: Site Editor Publish Time: 2018-04-02 Origin: Site
The motor driven by frequency converter is induction AC motor, also called AC asynchronous motor. Most of the motor used in industry is AC asynchronous motor. The rotating speed of asynchronous motor depends on the rotating speed of its stator rotating magnetic field, that is, synchronous speed. The so-called asynchronous, refers to its actual speed and synchronous speed is always close, but there is always a certain difference. The difference is called a slip. When the motor is running, the actual speed is slightly lower than the synchronous speed. The actual speed of the generator or brake is slightly higher than the synchronous speed.
The failure rate of frequency converter increases exponentially with the increase of temperature, and the service life decreases exponentially with the increase of temperature. The environment temperature rises 10 degrees, the frequency converter average service life halves. When the frequency converter works, the current flowing through the frequency converter is very large, and the heat generated by the frequency converter is also very large. The influence of its heat can not be ignored. Normally, the frequency converter is installed in the control cabinet. We need to know about the calorific value of an inverter. The following formula can be used to estimate the calorific value: the approximate value of calorific value = the capacity of the converter KW) × 55 [W].
Here, if the converter capacity is constant torque load (overcurrent capacity 150% * 60s) if the converter with a DC reactor or AC reactor, and also in the cabinet, the heat will be greater. The reactor is installed on the side of the inverter or above the test. At this time can be estimated: frequency converter capacity KW) × 60 [W] if there is a brake resistance, because the brake resistance heat loss, it is best to install the location and frequency converter isolation, such as installed on top or side of the cabinet, etc. .
At altitude above 1000m, because the air density is reduced, the cooling air volume of the cabinet should be increased to improve the cooling effect. In theory, the inverter should also consider reducing capacity by 5% per 1000m. Because the load capacity and heat dissipation capacity of the design inverter is generally larger than the actual use, it is also necessary to look at the specific application. Say 1500m, but periodic loads or short-running loads, such as elevators, are unnecessary. Frequency converter is composed of main circuit, power circuit, IPM drive and protection circuit, cooling fan and so on. Its structure is mostly in the form of unit or modularization. Because the usage method is not correct or the setting environment is unreasonable, it is easy to cause the frequency converter to misoperate and malfunction, or can not meet the expected operation effect. In order to prevent trouble in the first place, it is particularly important to carefully analyze the causes of the failure in advance.