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Low-pressure transducer basically controls fashion

From;    Author:Stand originally

Current, as the ceaseless maturity of low-pressure transducer technology, the applied circumstance of low-pressure frequency conversion decided its different classification. Sheet looks from technical angle, the control means of low-pressure transducer also expresses the technical genre that understands it on certain level. We analysed pattern of the following kinds of control here:
Wide modulation of sine arteries and veins (SPWM) its characteristic is control circuit structure simple, cost is inferior, physical characteristic hardness is better also, the flowing timing that can satisfy average transmission asks, already got applied extensively in each domains of the industry. But, means of this kind of control is when low frequency, because output voltage is inferior, torsion suffers stator resistor to control falling impact more remarkable, make output the biggest torsion to reduce. Additional, its physical characteristic does not have dc motive after all hard, dynamic torsion ability and static timing function still are like person meaning very much, and curve of not tall, control can follow systematic performance to change ladenly and change, torsion answers utilization rate of torsion of slow, electric machinery not tall, the because of the existence of stator resistor and effect of inverter dead band function when low speed drops, stability becomes poor to wait. Because this people excogitates vector again,control frequency control. But means of this kind of control also is one of control means that at present transducer uses generally. Also be at present card of home made product uses one of most control means.
Voltage space vector (SVPWM) it is with three-phase weaveform whole generates the effect to be premise, with approaching the ideal circle of electric machinery air gap to rotate magnetic field contrail is a purpose, generate three-phase modulation weaveform, less than cuts polygon to approach round means to have pilot. Via after practice is used, be being improved somewhat again, introduce frequency compensation namely, can eliminate speed pilot error; Pass amplitude of feedback estimation linkage, remove the effect of resistor of the stator when low speed; closed circuit of output voltage, electric current, in order to increase dynamic precision and stability. But control circuit link is more, and the adjustment that did not introduce torsion, so systematic performance did not get fundamental improvement. Because numerous and homebred transducer is on vector control,still have certain difference with foreign brand, because this SVPWM controls fashion,the transducer vector control in home is compared in means common.
The practice of vector control frequency control is the Ia of stator electric current below, Ib, Ic fastens asynchronous electromotor in three-phase coordinate, through three-phase - 2 photographs commutation, equivalent becomes the alternating current Ia1Ib1 that dormant coordinate department issues two-phase, repass presses rotor magnetic field directional change coming back is changed, equivalent rotates into synchronism the Im1 of dc electric current below coordinate department, It1 (the excitation electric current that Im1 is equivalent to dc motive; The armature electric current that It1 is equivalent to becoming direct ratio with torsion) , imitate the control method of dc motive next, get the control of dc motive to measure, turn over commutation through corresponding coordinate, realize the control of pair of asynchronous electromotor. It is AC motor equivalent is dc motive character actually, be opposite respectively speed, two heft undertake magnetic field be controlled independently. Through dominating rotor linkage, decompose stator electric current next and acquire torsion and magnetic field two heft, via coordinate commutation, realize orthogonality or solution Ou control. Use vector is controlled, can make electric machinery is in low speed, be like (when having speed sensor) 1Hz (right 4 extremely electric machinery, its rotate speed is 30r/min about) the torsion that the output torsion when can achieve electric machinery to be outputted in 50Hz power supply (most the 150 % that are rated torsion about) . To groovy V/F control, the voltage drop of electric machinery reduce and increase of speed relatively as electric machinery, because excitation is insufficient,this is brought about, and make electric machinery cannot obtain enough whirl force. To compensate this inadequacy, the need in transducer is passed heighten tension, will compensate the voltage drop that electric machinery speed is reduced and causes. This function is torsion promotion namely. Torsion promotes a function to heighten the output tension of transducer. However although heighten tension of a lot of output, electric machinery torsion can be not mixed its electric current rises relative to what answer. The torsion heft that because electric machinery electric current includes electric machinery,arises and other heft (be like excitation heft) . Vector controls a voltaic value electric machinery to undertake allocation, the heft of electric machinery electric current that produces torsion certainly thereby and heft of other electric current (be like excitation heft) numeric. Vector control can pass the response of the voltage drop that carries to electric machinery, undertake optimizing compensating, below the condition that does not add electric current, allow electric machinery to yield big torsion. This function is valid also to improving the temperature rise when electric machinery low speed. Vector controls means to because this makes foreign brand,also take a when lead high-end market significant advantage.
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