REGIMUL TRANZITORIU LA MASINA ASINCRONA MONOFAZATA

Scientific and Technical Bulletin, 2004Mller Valentin

Regimul trazzitoriu la maina sincron

THE VARIATION OF THE ROTORICAL PARAMETERS IN COMPANISON WITH THE FREQUENCY AT THE INDUCTIVE (ELECTRIC) MOTORMller Valentin

"Aurel Vlaicu" UniversityAbstract: In this paper it is shown the variation of the rotor resistance and the dispersion reactance , magnitudes reduced at the stator in copanison with the charge.1. IntroductionThe determination of the charging work characteristics is done, if we know all the parameters from the equivalent scheme in T, for the inductive (electric) motor, shown in figure 1.

Fig. 1 Equivalent scheme in T for the inductive electric motorThe parameters for the sketch below are:

the resistance of the statorical phase winding;

dispersion reactance of the statorical phase;

magnetizing rezistance;

magnetizing reactance;

the resistance of the rotor winding, reduced at the stator;

the dispersion reactance of the rotor winding, reduced at the stator.

In many simulations, the parameters are treated like to be steady at a frequency of f1=50 Hz.

These suppositions make that the final results given by the machine model, in a certain regime, clear-away from reality.

To take into account the influence of the rotorical frequency f2, on the rotorical parameters, improve the machine model, based on the equivalent scheme in T. We try to improve a new modality to find out which of the rotorical parameters are implicit functions to the rotorical frequevency. These determinations are made on the short-circuit evidence at a variable frequency [1].

In the mathematical relations of the resistance and reactance we introduce the corrective coefficients:

(1)

(2)

where:

(3)

(4)

(3)

(4)

(5)

(6)

(7)

In this relations , , , are coresponding to a nominal frequency (f1=50 Hz).

2. Experimental paragraphWe consider a triphases asynchronous motor, with a nominal power PN=4 KW at 1500 rot/min, supplies by a nominal voltage U1=220 V.

The electrical parameters found-out on the schort-circuit evidence and discharge working regime at a frequency of 50 Hz (regime) are next:

; ; ;

; ; .

In figure 2 it is shown the variation of CR and CX coefficients in comparison with the rotorical frequency. In figure 3 it is shown the rotorical impedance deviation, to rotorical impedance at a frequency of 50 Hz.

3. ConclusionsThe corrective coefficients CR and CX that we introduce in the relations (1) and (2) have major variations, from 010 Hz.

In figure 1.3 is the value of the rotorical impedance is calculated at the nominal frequency.

As we have already expected important variations of the rotative impedance are at low frequency from 010 Hz.VARIAIA PARAMETRILOR ROTORICI N RAPORT CU FRECVENA LA MAINA DE INDUCIE

Mller Valentin

Universitatea "Aurel Vlaicu" AradRezumat: n aceast lucrare se prezint variaia n raport cu sarcina, a rezistenei rotorice i a reactanei de dispersie , mrimi reduse la stator.

1. Introducere

Determinarea caracteristicilor de funcionare n sarcin se poate face dac se cunosc parametrii din schema echivalent n T a mainii de inducie, reprezentat n figura 1.

Parametrii corespunztori schemei prezentate, sunt:

rezistena nfurrii fazei statorice;

reactana de dispersie a fazei statorice;

rezistena de magnetizare;

reactana de magnetizare;

rezistena nfurrii din rotor, redus la stator;

reactana de dispersie a nfurrii din rotor, redus la stator.

n multe situaii, parametrii se consider constani la frecvena de f1=50 Hz. Aceste ipoteze fac ca rezultatele finale date de modelul mainii ntr-un anumit regim s se ndeprteze de realitate.

Considerarea influenei frecvenei rotorice f2 asupra parametrilor rotorici mbuntete semnificativ modelul mainii, bazat pe schema echivalent n T.

Se are n vedere o modalitate de determinare a parametrilor rotorici considerai ca funcii implicite de frecvena rotoric. Determinrile se bazeaz pe proba de scurtcircuit la frecvena nominal [1].

n relaiile rezistenei i reactanei rotorice se introduc coeficienii de corecie:

(1)

(2)

unde:

(3)

(4)

(3)

(4)

(5)

(6)

(7)

n aceste relaii , , , corespund frecvenei nominale (f1=50 Hz).

2. Partea experimentalSe consider un motor asincron trifazat, avnd puterea nominal PN=4 KW la 1500 rot/min, alimentat la tensiunea nominal U1=220 V.

Parametrii electrici determinai din proba la scurtcircuit i gol la frecvena de 50 Hz sunt urmtorii:

; ; ;

; ; .

n figura 2 se prezint variaia coeficienilor CR i CX n raport cu frecvena rotoric.

n figura 3 se prezint abaterea impedanei rotorice fa de impedana rotoric la frecvena f1=50 Hz.

3. ConcluzieCoeficienii de corecia CR i CX care se introduc n relaiile (1) i (2) au variaii importante n domeniul 010 Hz.

In figura 1.3 reprezint valoarea impedanei rotorice calculate la frecvena nominal. Aa cum era de ateptat variaii importante ale impedanei rotorice sunt la frecvena mici n domeniul 010 Hz.

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