On a number of technologies to improve the converter performance - inverters, and Technology - Electrical industry

China Product


1 Introduction Present, China Inverter Produced by manufacturers Inverter Mostly the ordinary V / f control mode, with only a few of foreign claim to use vector-based speed control technology. Basically in the foreign brands to open-loop, closed loop, speed control of three-dimensional control thought, in particular, concern is ABB's DTC control method in the product has been successfully applied. Frequency Control System domestic academic research has been done a lot of relevant work, and taken certain results, but it works compared to overseas practice and the accumulation of a gap there. If the theoretical knowledge into industrial products to our existing practice, frequency control products to improve our performance and quality, is a more pressing problem worthy of study. This paper attempts to control two aspects of strategy and modulation current of V / f control and techniques of the comparison indicates that, for all to share and explore.





Usually V / f controlled inverter system structure, modulation, the main circuit composed of three parts, of which pulse width modulation control part and the part of all of the software algorithm. This control method is drawn against AC motor steady-state model, not dependent on motor parameters and changes, and thus control is simple, easy to implement. However, the relatively narrow speed range, only applies to fans, pumps and other less demanding load on the speed performance. In order to improve load capacity slow times and the system dynamic performance, to meet the needs of real industrial field, to the existing control methods and the corresponding pulse width modulation strategy to improve and enhance. The following key technology for a few were discussed.
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2 control strategy in a number of technical


2.1 Compensation Compensation technology in open-loop control is indispensable. It includes the torque compensation, slip compensation, and compensation of dead time effect. Stator resistance at low pressure drop when compared to the output inverter is no longer ignore the need to compensate, otherwise the output voltage is not enough, the motor in low speed when the fixed or decreased. Slip compensation mainly for motor load is large in the actual output speed will be lower than the set speed and design. The two compensation methods can be used in practice, a simple fixed-value compensation, improved methods used to calculate three phase motor current compensation, but only under the current amplitude of the compensation is in fact the scalar compensation; more accurate compensation method is to conduct three-phase alternating current motor vector resolution, while the loss of participation in motor terms, such compensation is better. But this method is more complicated, while some of the motor parameters are dependent, in some difficulties in the implementation process.





Dead time effect compensation technology in open loop control plays an important role, it can effectively improve the output current waveform of the smoothness and reduce harmonics, while the output voltage can increase motor current RMS and reduce the shock. Especially in the required quiet environment, man-made increased carrier frequency, if not dead time compensation, even if the motor load in the low frequency may not run. Now commonly used with dead zone compensation of zero current direct compensation method, based on stator flux current decomposition, the dead zone voltage pulse width compensation, non-current Sensor Dead time compensation prediction methods. Determine the compensation current zero-crossing method is simple and easy to implement, but due to large current waveform in the noise component, while the external load fluctuations and will cause any interference with the judge had zero errors, zero has a dead platform affects the low frequency compensation effect, in particular, relatively high carrier frequency is particularly significant. Based on stator flux orientation methods do not directly determine the current zero-crossing, but the stator current in the rotating coordinate system by current vector angle and the decomposition of dead relationship between the voltage vector corresponding compensation, if the method and the dead-voltage pulse width of combination, the effect is more prominent. Phase angle prediction dead-time compensation method is a current sensor saved fixed compensation method, which first predicted the current phase angle, and then the dead time compensation accordingly, can predict the angle of inverter output capacity of different settings in the software or set by external changes.

Development and puffing machine in the Expanded Foods - air puffing machine, puffed food - Food Industry

China Product


Generation re-refined grain and less coarse grains Diet Habits, has been a serious threat to human health, many experts and scholars put forward the "Security" "nutrition" "Health" of the diet of new ideas, to restore thousands of years of "grain-based" diet idea. Currently on the market with "grain Cereal "To Raw material Food after another, a new philosophy of life is being gradually extended and accepted by the people to gradually improve the national physical fitness, improve the national life and quality of life.





Currently very popular food market selling rice wheat pass through, milky corn, coffee, corn and other "whole grains" Snack Food , To meet the new consumption concept, but also popular among consumers, in fact, these foods are in our local food traditions developed in the food production process in the most relevant health materials puffing, puffing process in maintaining safe and secure pollution, while maintaining the nutritional content of whole grains, color and flavor, air puffing machine can achieve such good purpose. Dole Food Co., Ltd., Wuhan, Hong to since the establishment of dedicated research of traditional Chinese food, and Huazhong University of Science and professor of Huazhong Agricultural University, several experts Cooperation Development of the market LO's = Food Machinery And food technology developed formula to ensure food technology and food machinery supporting formulas, practical, advanced.
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Before 2004, China's grain puffing has been the use of traditional air tank, and has been confined to Rice Puffing, a Expanded only 1 kg, not only yield a small, but also time-consuming work, easy to damage, and serious food most of the lead exceeded. Wuhan to Seoul Food Machinery Co., Ltd. Hong After nearly three years of painstaking development, refer to Japan, Taiwan's air puffing similar products, and finally in September 2006 developed the first large-scale air puffing machine, widely used in rice, wheat, barley, maize, sorghum, Beans And other grain puffing, after numerous experiments, and the use of the top ten customers feedback, the company has made many technical improvements compared to traditional air tank has the following advantages: large output, one can be extruded 8kg of rice; saving time and labor , a worker can operate 2; save energy, lower unit product energy consumption; safe operation, four security insurance, provincial qualified.





In June 2008, the market appeared in counterfeit goods, and later after the company investigated a number of small self-employed the original copy of our products and technology act, Changsha two businesses with their publicity pictures and web images to mechanically copy, the only immediate interests of the speculators do not take into account the interests of customers, shoddy, with a puffing with three iron tanks on the assembly welding, there is no concept of quality and safety products to customers has posed a great loss and unnecessary troubles, such as Jilin, first up on food in unknown circumstances in the purchase of 10 sets air puffing machine, less than a month can not use all the freight had to spend back in Changsha.





The soul of enterprise development is the "innovation", the production line with the market and consumers like the food is always fighting for food companies! Wuhan to Seoul Food Machinery Co., Ltd. Hong has followed the market, different shapes of rice through the automatic molding wheat food use through computer control, advanced design, stable no impact, no shaking, solves such problems as domestic counterparts slow vibration , mold and hopper were designed using food-grade material production, safety and health, forming the system of electronic eye tracking alignment, two mechanical correction, positioning accuracy, high yield; material automatically cloth, automatic feeding, automatic ejection, defective low. Since entering the market welcomed by the majority of food plants, in many parts of the country are well-known brand partners. <<"Check more exciting content





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Experienced extremely dry 2009 Chinese wheat market price trends