In the actual production process, why do motors driven by frequency converters overheat? This is because the voltage driven by the inverter contains rich high-frequency components.
The voltage waveform of the inverter-driven motor is not a sine wave voltage, but a pulse width modulation (PWM) voltage. According to Fourier analysis, this waveform contains rich high-frequency components. The main frequency component is the repetition frequency of the PWM pulse and its integral multiple frequency. The repetition frequency of the PWM pulse is called the carrier frequency of the inverter.
Different frequency converters have different carrier frequencies, generally 1~12kHz. For a PWM voltage with a carrier frequency of 1kHz, the current flowing into the motor is mainly current at frequencies of 1kHz, 2kHz, 3kHz, 4kHz, and 5kHz. These high-frequency currents increase motor winding losses and core losses. Theoretical analysis shows that the loss of the winding is proportional to the square root of the frequency, and the loss of the core is proportional to the square of the frequency. Therefore, when such a high-frequency current flows through the motor, the loss of the core increases sharply, leading to overheating.
The solution to motor overheating is to reduce the high-frequency component of the motor drive voltage. The way to achieve this is to install a SWF sine wave filter at the output end of the frequency converter. The sine wave filter converts the PWM voltage waveform into a sine wave voltage waveform adapted to the motor, thus eliminating the phenomenon of motor overheating.
The sine wave filter will emit larger noise and be accompanied by higher temperature. These are normal phenomena. It can be considered that it is the sine wave that takes up the energy that causes the motor to emit noise and increase the temperature, thus protecting the motor.
When purchasing a sine wave filter, you must understand the carrier frequency of the frequency converter, otherwise it may cause adverse consequences. For example: The temperature of the hoist is very high, accompanied by loud noise, and I hope to make adjustments. This is a very typical problem, just install a SWF filter. Before purchasing the filter, the information provided by the hoist manufacturer is that the carrier frequency of the frequency converter is 2kHz. But after installation, it was found that the noise was louder and the motor temperature was higher.
After actual testing, it was found that the actual carrier frequency of the frequency converter is 1kHz. The parameters of the sine wave filter need to be modified again. After modifying the parameters, the whistling sound of the motor basically disappears and the temperature drops from the original 65℃ to 53℃. Reducing the temperature of the motor is very beneficial to extending the life of the motor. In addition, after installing a sine wave filter, it can also eliminate bearing current and extend the life of the motor.
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