Power Electronic

The variable frequency drives  is a power control device that converts the power frequency power supply into another frequency by using the on-off function of the power semiconductor device. The correct selection of the frequency converter is very critical to the normal operation of the control system. Usually we need to consider the matching problem with the motor, load type, site environment and so on when we select the inverter. Below we will specifically introduce what factors need to be considered when selecting an inverter. Variable frequency  drives considerations for selecting  1. Determine the purpose of frequency conversion: constant voltage control or constant current control, etc. 2. The load type of the inverter: such as vane pump or positive displacement pump, etc.. Pay special attention to the performance curve of the load, which determines the method of application. 3. Select the inverter according to the actual working current of the motor The actual work...

  What are the interference methods of the frequency inverter and how to deal with them?   Divided by the way of transmission ：   a. Radiation interference b. Conducted interference     Anti-interference measures:   ✔ For the interference signal transmitted by radiation, it is mainly weakened by wiring and shielding the radiation source and the line to be interfered. ✔ For the interference signal transmitted through the line, it is mainly dealt with by adding filters, reactors or magnetic rings on the input and output sides of the converter.     The specific methods and precautions are as follows:   a. Signal lines and power lines should be vertically crossed or routed in separate slots. b. Do not use wires of different metals to connect to each other. c. The shielding tube (layer) should be grounded reliably, and ensure continuous and reliable grounding over the entire length. d. Twisted pair shielded cable should be used in the signal circu...

  What are the functions of a soft starter?   Overload protection:    The soft starter introduces a current control loop, so it can track and detect the change of motor current at any time. By increasing the setting of overload current and the inverse time limit control mode, the overload protection function is realized. When the motor is overloaded, the thyristor is turned off and an alarm signal is issued.     Phase loss protection:   During operation, the soft starter detects the change of the three-phase line current at any time, and can make a phase loss protection response once the current is cut off.   Overheat protection:    The temperature of the thyristor radiator is detected by the internal thermal relay of the soft starter. Once the temperature of the radiator exceeds the allowable value, the thyristor is automatically turned off and an alarm signal is issued.   Other functions:   Through the combination of electron...

  We usually refer to the device that converts alternating current with constant voltage and frequency into alternating current with variable voltage or frequency as "frequency inverter". A frequency inverter can also be defined as follows: VFD (Variable-frequency Drive) is a power control device that uses frequency conversion technology and microelectronics technology to control the AC motor by changing the frequency of the motor's working power supply. The working principle of inverter is generally: 1. Convert three-phase or single-phase alternating current to direct current (DC) 2. Convert direct current (DC) to three-phase or single-phase alternating current (AC). 3. The inverter changes the output frequency and voltage at the same time, that is, the n0 on the motor running curve is changed, so that the motor running curve moves down in parallel. Therefore, the inverter can make the motor obtain a larger starting torque with a smaller starting current, that is, the in...

Since the voltage waveform output by the inverter is similar to a sine wave, it is by no means a real sine wave. The waveform contains a lot of harmonic components, especially the high-order harmonics will increase the output current of the inverter, cause the motor winding to heat up, generate vibration and noise, accelerate insulation aging, and may even damage the motor. At the same time, the harmonics of various frequencies will emit different degrees of radio interference into the space, therefore, it may cause the malfunction of other electromechanical equipment. Therefore, when installing the inverter, it is necessary to comprehensively consider the distance between the central control room, the inverter, and the motor in order to minimize the influence of harmonics and improve the stability of the control. 1. The distance between VFD and motor Close distance:  the distance between the inverter and the motor is  ≤20m ; Middle distance:  The distance between the in...