The net side harmonic of general transducer reachs its the way to deal with a situation

The generation of harmonic electric current is three-phase complete wave to cannot accuse rectification commonly as a result of the rectification part of transducer, dc loop uses large electric capacity to serve as filter. Such, although the weaveform of voltage of net side input of transducer basically is sine wave, but the charging current that input electric current is pulse type, contain rich harmonic. Its weaveform is shown 1 times like the graph. Graph the input voltage of 1 transducer and voltaic weaveform the weaveform of electric current of transducer net side is mixed by impedance of circuit total equivalent advocate the voltage of two end decides electric capacity jointly, suffer the effect of parameter of diode commutator itself at the same time. Additional, closely related size of its electric current and weaveform and dc side voltage, and dc side voltage can change as load again and fluctuate. Accordingly, through analytic expression is calculated mensurably electric current of transducer net side compares difficulty, not practical also on the project. When general analysis, can use simplifying approximate method to calculate. 2.

The impedance of road of bus line of concern net side of harmonic electric current and circuit impedance is bigger, input electric current is more flowing, harmonic electric current is smaller. Accordingly commonly used dc or communication reactor increase circuit impedance, improve weaveform of input electric current thereby. After joining reactor, input aiguille decrescent of electric current, at the same time of diode guide connect time to lengthen, because this can reduce the content of harmonic of net side electric current of transducer. Dc reactor and communication reactor can be used at restraining harmonic, but both each have a characteristic. The reactor accessory FR-BEL with transducer of 3 water chestnut (dc) with FR-BAL (communicate) for for the exemple bright both the similarities and differences between. Its use a result to see a table 1. Express 1 communication reactor and dc reactor to use the effect to compare 3.

When weaveform of net side electric current and the relation transducer load of straight voltage drifting side change, can affect dc side voltage. Be more than in rectification voltage only advocate capacitance the voltage of two end (Ed) when, rectifier just can have input electricity. Accordingly, the size of volts d.c. can decide the electric width of diode commutator. Watch 2 gave out the relation between weaveform of transducer input electric current and volts d.c. . Express 2 transducer to input the relation between weaveform and volts d.c. to express 2 in, undee coefficient and token of peak value coefficient input distortion degree of electric current, the power input factor of transducer is defined to be total power input and apparent power than. Mix as a result of input voltage again of electric current base wave is phasic and main identical, the influence with oversight lopsided three-phase, can get ILI/IL of λ L ≈ namely power factor is approximated base of wave electric current and total electric current than. Because this is expressed 2 also can reflect the concern between dc side voltage and power factor. 3, the countermeasure that restrains Gao Cixie wave 1.

In electric current of input of transducer of relevant state level occasionally second harmonic and content of 3 times harmonic are very small, general far under GB, 5 in basically inputting electric current in order to analyse because of this article, 7, 11, 15, 17, 19 times harmonic electric current is exemple. According to national level GBT14549, 93 " electric energy quality is public harmonic of electrified wire netting " with GB12668.

3, 2003 " the electromagnetism compatibility standard of product of electric transmission system reachs timing its specific experiment means " , communal join is nodded (PCC) harmonic electric current is restricted value and power source short-circuit current and the biggest base wave of load current than relevant. If express,each below capacity of fiducial short circuit harmonic electric current allows a value 3 are shown. Express electric current of each harmonic below capacity of 3 fiducial short circuit to allow a value among them, capacity of fiducial short circuit (Sj) it is with the relation of voltage 0.

38kV ～ 10MVA; 6kV10kV ～ 100MVA. The harmonic electricity that uses in the article is restricted to be worth for GBT14549 ～ 93 in electric current of each harmonic below capacity of fiducial short circuit allows a value, and GB12668.

The bounds that the index that 3 ～ give out in 2003 appendices B falls each harmonic electric current for different Rsc is worth (% ) , both and OK mutual convert, the user can choose according to his actual condition proper motion. 2.

The data that the harmonic content when different system is configured provides according to electric machinery of 3 water chestnut, when transducer of commutate of bridge of use diode three-phase, if the harmonic content below different configuration expresses 4 to show. Express content of 4 harmonic electric current 4, harmonic galvanometer calculates a method 1.

The place before computational measure is like is narrated, the harmonic electric current of transducer passes analytic formula very hard to calculate directly. Method of a kind of calculation is recommended below, consult for everybody. Measure 1: The each harmonic electric current that allows according to the computation of short circuit capacity of national level and actual transformer, specific formula is Ih=IGB (Sr/Sj) in type: Ih allows to be restricted to be worth for each harmonic electric current; IGB issues each harmonic electric current to be restricted to be worth for capacity of fiducial short circuit; Sr is capacity of actual short circuit, MVA; Sj is capacity of fiducial short circuit, 10MVA is taken when 380V. Allocate of the consultative capacity that every user that same and communal join nods allows a value to be in by this user this a little bit to the harmonic electric current of infuse of electrified wire netting or peak load capacity and capacity of equipment of its power supply than undertaking. If use the method that arithmetic of harmonic electric current mixes simply, gotten result often too conservative, what can cause resource is wasteful. Recommend the method of sue for peace of use bogus square, have Ihi=Ih namely (Si/St) in 1/a type: Si is the capacity of the agreement that use phone of the user or peak load capacity, MVA; St is capacity of power supply equipment, MVA; The each harmonic electric current after Ihi is convert allows a value; A is phasic overlay coefficient, by the watch 5 undertake extraction a cost. If the phasic overlay coefficient of each harmonic expresses 5 to show. The measure of phasic overlay coefficient that expresses each 5 harmonic 2: I of convert of rated electric current ' E=Ie × (0.

38 standards voltage) in type: I ' the rated electric current after E is convert; Ie is the rated electric current of transducer. Measure 3: The basis is expressed 4 and the size that the circuit form of transducer will come to decide each harmonic electric current, compare of 1 as a result with measure, whether does judgement accord with GB. Computational formula is as follows: Ih=I ' content of E × harmonic (% ) if × load rate does not accord with GB, should use other the way to deal with a situation, if use reactor, add harmonic to compensate equipment to wait. 2.

Example analyses power supply system (10kV) short circuit capacity is 10MVA, capacity of total power supply is 1MVA. Capacity of some user agreement is 0.

5MVA. If some user uses a transducer only, its model is FR-A540-45K, laden rate is 80% , analyse its harmonic electric current to whether satisfy national standard. Computational process is as follows. (1) basis Ih=IGB (Sr/Sj) with the watch 3, if the watch is shown 6 times,the bounds after getting convert easily is worth. The bounds after expressing 6 convert is worth next according to formulary Ihi=Ih (Si/St) 1/a and watch 5, computation gets the each harmonic electric current of this user is restricted to be worth is opposite answering, be like I5=2 × (0.

51) 1/1.

2=1.

12 calculate respectively each harmonic electric current is restricted to be worth, those who get this user is the biggest if the watch is shown 7 times,allow harmonic electric current. Watch 7 the biggest allow harmonic electric current (the rated electric current that 2) checks transducer manual to get this transducer: Ie=86 (A) convert arrives 10kV side: I ' E =Ie × (0.

3810) =3.

27 (A) (when 3) is not taking reactor, have I5=3.

65% × of 27 × 80%=1.

7 (A) use dc reactor (DCL) when, have I ' 5=3.

30% × of 27 × 80%=0.

78 (A) manage together, calculable get expressing 8 medium data. Comparative watch 7 with the watch 8 can discover, when using dc reactor, exceed bid 5 times with 7 harmonic. If use dc reactor, can satisfy harmonic standard. 5, the harmonic that the last word applies middling actually to use restrains measure, outside the use reactor that alludes besides above paragraphs place, still basically have 12 looks rectification and use can charge the means such as rectification. But because general transducer uses these circuit develop rarely,attack structure, so no longer enumeration. Harmonic problem is obstacle of a when transducer remains to solve in development process main technique all the time. Come nearly two years, had begun to appear a few use new circuit develop to attack of the structure commercialize low-pressure transducer product, be like 3 n transducer, matrix type transducer (MC) wait. Believe as cost reduce the settlement with difficult problem of a few technologies, in future 5 ～ inside 10 years, harmonic of transducer net side this one difficult problem gets hopeful be settlemented effectively, transducer also will make a magic figures drawn by Taoist priests to invoke or expel spirits and bring good or ill fortune actually " green power source " . CNC Milling CNC Machining