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What is the inverter? What is the principle of the converter? What is the structure of the converter
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What is the inverter? What is the principle of the converter? What is the structure of the converter?There are a lot of learning electrician's novice friends may be the first contact with the inverter, so the inverter will have a question. Today, electrical learning network to talk about the small series of knowledge about frequency converter, we want to help!
1 what is the frequency converter?
Inverter (Drive Variable-frequency, VFD) is the application of frequency conversion technology and microelectronics technology, by changing the motor power frequency mode to control AC motor power control equipment. Inverter is mainly composed of rectifier (AC inverter), filter, inverter (DC AC), brake unit, driving unit, detection unit, and so on. Inverter by internal IGBT disconnected to adjust power output voltage and frequency, according to the actual needs of the motor to provide the power supply voltage, so as to achieve the purpose of energy-saving and speed. In addition, inverter and a lot of protection, such as over-current, over-voltage, overload protection and so on. With the continuous improvement of the degree of industrial automation, frequency converter has been widely used.
2 converter working principle is what?
The main circuit is for induction motors provide voltage variable frequency power source power conversion part, the main circuit of the inverter in general can be divided into two categories: voltage is the voltage source DC converter for AC inverter, the DC loop filter capacitance is. Current mode is the DC converter of the current source converter for AC frequency converter, the DC circuit filter is the inductor.
3 frequency converter structure is what?
Rectifier
The use of a large number of converter, which transforms the power frequency power supply to DC power supply. Two sets of transistor converters can be used to form a reversible converter, which can be used for regeneration because of its power direction.
Flat wave circuit
In the DC voltage of the rectifier, the ripple voltage is 6 times the frequency of the inverter, and the ripple current generated by the inverter also makes the DC voltage fluctuation. In order to suppress the voltage fluctuation, the inductance and capacitance of the pulse voltage (current) are used. Device capacity hours, if the power supply and the main circuit components of the device has a margin, you can save the inductance using a simple flat wave circuit.
Inverter
In contrast to the rectifier, inverter is the DC power conversion to the required frequency of the AC power, in order to determine the time to make 6 switches on the switch, turn off the 3 phase AC output. The voltage type PWM inverter for example to show the switching time and voltage waveform.
The control circuit is to provide a loop control signal to the asynchronous motor power supply (voltage and frequency regulating main circuit, it has the frequency, the voltage "operation circuit", the main circuit of the "voltage and current detection circuit, the motor" speed detection circuit, operation circuit of control signal amplification drive circuit ", and the inverter and the motor" protection circuit.
(1) computing circuit: the external speed, torque and other instructions with the detection circuit of the current, voltage signal for comparison, determine the inverter output voltage, frequency.
(2) voltage and current detection circuit: voltage, current, etc.
(3) the driving circuit: a circuit for driving the main circuit device. It is isolated from the control circuit and the main circuit device is turned on and off.
(4) speed detection circuit: to install in asynchronous motor shaft machine speed detector (TG, PLG) signal for speed signal into the computing circuit. According to the instruction and operation can make the motor run in the speed command.
(5) protection circuit: detecting the voltage and current of the main circuit, when an abnormal, such as over load or over voltage, in order to prevent the inverter and asynchronous motor damage.
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