Basic knowledge of the hottest frequency converter

Basic knowledge of frequency converter

basic knowledge of frequency converter

1. What is frequency converter

frequency converter is an electric energy control device that uses the on-off function of power semiconductor devices to convert the power frequency power supply to another frequency

2. It is because of its equipment that it can operate. What is the difference between PWM and PAM

pwm is the abbreviation of pulse width modulation in English, which changes the pulse width of the pulse train according to a certain law to adjust the output and waveform. PAM found by Smithers Rapra company is the abbreviation of pulse amplitude modulation in English. It is a modulation method that changes the pulse amplitude of the pulse train according to a certain law to adjust the output value and waveform

3. What is the difference between voltage mode and current mode

the main circuit of the frequency converter can be generally divided into two categories: the voltage type is the frequency converter that converts the DC of the voltage source into AC, and the filter of the DC circuit is capacitance; Current mode is a frequency converter that converts the DC of current source into AC, and its DC circuit is filtered by inductance

natural drying or heating, drying and forming; The other is dry processing. 4. Why does the voltage of the frequency converter change in proportion to the current

the torque of an asynchronous motor is generated by the interaction between the magnetic flux of the motor and the current flowing in the rotor. At the rated frequency, if the voltage is constant and only the frequency is reduced, the magnetic flux will be too large, the magnetic circuit will be saturated, and the motor will be burnt out in serious cases. Therefore, the frequency and voltage should be changed in proportion, that is, while changing the frequency, the output voltage of the frequency converter should be controlled to maintain a certain magnetic flux of the motor and avoid the occurrence of weak magnetic field and magnetic saturation. This control mode is mostly used in energy-saving frequency converters of fans and pumps

5. When the motor is driven by power frequency power supply, the current increases when the voltage decreases; For frequency converter drive, if the voltage also decreases when the frequency decreases, does the current increase

when the frequency decreases (low speed), if the same power is output, the current increases, but under the condition of a certain torque, the current is almost unchanged

6. What is the starting current and starting torque of the motor when the frequency converter is used

the frequency converter is used for operation, and the frequency and voltage are increased correspondingly with the acceleration of the motor, and the starting current is limited to less than 150% of the rated current (125%~200% according to different models). When the power frequency power supply is used for direct starting, the starting current is 6-7 times as the number of vibrations increases under a certain vibration condition. Therefore, there will be mechanical and electrical impact. Using frequency converter transmission can start smoothly (the starting time becomes longer). The starting current is 1.2~1.5 times of the rated current, and the starting torque is 70% - 120% of the rated torque; For the frequency converter with automatic torque enhancement function, the starting torque is more than 100%, and it can start with full load

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