A Study On High Power High Speed Varying-Frequency Stirrer

The liquid state materials such as drilling slurry need to be stirredin high speed in order to make the different material get enough dispersionand uniformity before the experimentation. This is important andnecessary for the research and in-situ using of additive used in petroleumdrilling ,chemical combination,foodstuff process and building coating.Depending on the difference of material, the stir time and speed is alsodifferent. Direct current concatenated motors are mainly used to providethe drive power before the technology of speed regulating by frequencyconverting is mature. And this result some problems as below. (1) Because the direct current concatenated motors use the carbon brushand slipper to change the AC (alternating current) to DC(directcurrent), so when its speed exceed 3000rpm(revolutions per minute),it will make out harsh noise. Long-term usage of it will injure theears of experimenter seriously. (2)Based on the same reason, the large working current of the directcurrent concatenated motors can make its rotator more easily to beburned and result low use life.(3)The spark come from the working direct current concatenated motorsmake it not suitable for using in the palace where contain some kindof dangerous gas.(4)It also need to clear the accumulating carbon and change the carbonbrushes, so it is not very inconvenient for use.(5)Its narrow speed regulation induce its speed can not be regulatedeasily in the wide range of 0 to 15000rpm.The author of this paper used the latest technology developingproduction-speed regulating by frequency converting to design and makethe high power high speed varying-frequency stirrer. The new controltechnology about the speed regulation of motor by changing the frequencyand amplitude of the voltage which used to drive the motor is discussed.High power digital frequency-converting speed regulator is designed byusing the single chip computer 89C51 as the control core. This design alsouse the SA866 special purpose SPWM controlling chip and PS21255 IPM powermodule as the mainly controlling module. Inverter-duty motors with thespecialty of small volume and high power are designed. The problem ofmultistage harmonic suppressing for speed regulating by frequencyconverting and the problem of heat dispersion and noise suppressing forsmall high power high speed inverter-duty motor are settled. Three kindof high power high speed varying-frequency stirrers are developed. Thiskind of series stirrers have many specialties: high power, small volume,low noise, wide range speed regulation, fast dynamic response, highefficiency, free maintenance, easy and convenient operation and so on.The stirrers have been used in the test laboratory of Technical Centerof China Oilfield Services Limited and other companies. This has made goodsocial and economic benefits.