A Variable Frequency Drive (VFD) utilizes变频 technology and microelectronics to control the power control unit of an AC motor by altering the motor's operating frequency. It is primarily composed of a rectifier (AC to DC), filter, inverter (DC to AC), braking unit, drive unit, and a microprocessor for detection devices. The converter adjusts output power voltage and frequency by internally disconnecting the IGBT to achieve energy-saving control. Additionally, VFDs offer multiple protection functions such as overcurrent, overvoltage, and overload protection. So, what is the principle of a VFD? Here's how it's wired! Take a look!
What is the principle of a variable frequency inverter?
1. The main circuit converts electrical energy into adjustable voltage and frequency power supply for asynchronous motors. Typically, the main circuit of a converter can be divided into two categories: voltage type, which converts DC from a voltage source into AC using a variable frequency inverter, with capacitors as the DC circuit filter; and current type, which converts DC from a current source into an AC variable frequency inverter, with inductors as the DC circuit filter.
2. The system consists of three components: a rectifier that converts AC power to DC power, a smoothing circuit that absorbs voltage fluctuations generated by variable frequency drives and inverters, and an inverter that converts DC power to AC power.
3. To understand the wiring method of a variable frequency converter, one must first comprehend what it is. A converter is a motor speed control device that can output different voltages and frequencies, thereby altering the speed of the motor. In this regard, it is essentially a variable AC power supply, capable of receiving commands to control high-power sources. High-power sources are inherently a type of power conversion technology that requires a high-power input source, thus necessitating the so-called main circuit circuit.
Variable Frequency Drive Wiring:
1. Power should be connected to the variable frequency drive's input terminal R.S.T, not at the converter's output end; otherwise, the drive may be damaged. After wiring, all loose wire ends must be cleared to avoid abnormal conditions and malfunctions. The variable frequency drive should be cleaned regularly. Please note that when drilling holes in the control panel, do not allow debris to enter the converter.
2. Between the wiring + and PR, do not connect anything other than the suggested braking resistor, and ensure there is no short circuit.
3. Interference from electromagnetic waves: The input/output (main circuit) of the inverter contains harmonic components, which can interfere with communication equipment near the inverter. To minimize interference as much as possible, install an FR-BIF or FR-BSF01 or FR-BLF line noise filter.
4. During long-distance wiring, the influence of charging current due to wiring parasitic capacitance can reduce the current limiting function of the rapid response current, leading to maloperation faults on the secondary-side instruments. Therefore, the maximum length of the cable should be less than the standard. If it is necessary to exceed the connection length, please set Pr.156 to 1.
Above is an explanation of what the principle of a variable frequency inverter is and how it is wired. For more information, please stay tuned for our subsequent articles.
