Motion control has obvious period characteristics, it is a variety of high-tech generalization, used to push industrial automation, office automation and home automation to a higher stage. At present, motion control is mainly composed of three parts: Variable-frequency Drive (VFD), motor and controller.
1. VFD local
At the heart of the VFD are the power electronics and the way they operate.
1) Power electronic equipmentPower electronic equipment is the equipment that plays the effect of on-off in the circuit and completes various converters, VFD is the installation of this converter, so it is unfolded with the development of inverter equipment, and the quality of inverter equipment depends on its on-off ability, and accepts the on-off current and rated voltage; In the on-off process, the size of the loss, such as saturation, voltage drop and switching loss, determines the efficiency and volume of the VFD. Switching losses are related to the switching frequency; The switching frequency is related to noise, and is related to the output voltage and current waveform. That is to say, power electronic equipment should be deployed in the direction of high voltage, high current, high switching frequency and small conduction voltage drop. The thyristor is a semi-control device, which belongs to the first generation of products, but the modulation frequency is low, the control is messy, the efficiency is low, the capacity is large, the voltage is high, and the history is long, whether it is used as a rectifier or as an inverter, it is relatively sophisticated.
The application of GTO thyristors and BJTs, whether assembled DC choppers or assembled VFDs, has a monopoly in the application of GTO thyristors in electric locomotives. This is also a serious scientific research topic that China organized to tackle during the Eighth Five-Year Plan period. However, the use of GTO thyristor VFD for other central centers is controversial because the turn-off current gain of the GTO thyristor is too small, the overcurrent protection is difficult, and the modulation frequency is low. DC choppers and PWMVFDs assembled with BJT are very popular, but the output voltage does not exceed 460V and the capacity does not exceed 400kW. BJT is a current drive, with high power consumption, low modulation frequency, and high noise, which is not as simple and reliable as the voltage drive of MOSFET. However, the latter has a smaller capacity and a lower output voltage, and there are not many competitive products in the market.
In motion control, the new generation of power electronics are IGBT and MCT: the former is MOS-driven BJT, which has the advantage that the capacity and voltage exceed BJT, and there is a tendency to replace it; The latter MOS drives thyristors and theoretically has the advantages of both. These two new equipment have sophisticated products, IGBT has been developed to the fourth generation, and now foreign countries are transferring the consumption process of microelectronics to power electronics, so the production of application-specific integrated circuits (). The intelligent equipment that combines the drive circuit and the protection circuit of the IGBT is called IPM, and the IPM that combines the switching power supply, so that the VFD is more reliable, and it has become the leading product of speed regulation in the past, which will replace DC speed regulation, and the 21st century will be a period of communication speed regulation.
2) Control methodVFD adopts different control methods, with different speed conditioning functions, characteristics and uses. The control method is roughly divided into open-loop and closed-loop control. Open-loop control includes U/f (voltage and frequency) proportional control; The closed loop includes slip frequency manipulation and various vector manipulations. From the perspective of pre-development history, it is also from an open-loop to a closed-loop. The general vector control is comparable to the armature current control of a DC motor. Now the communication motor parameters can directly stop the direct torque control, which is convenient and accurate, and the control accuracy is high.
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1. Problems of the inverter and the motor itself;
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Power picking
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1. Test preparation:
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E.oC3
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