DETERMINAREA SOLENAIEI DE EXCITAIE A UNUI GENERATOR SINCRON PE CALE MATEMATIC

Buletinul AGIR nr. 4/2012 octombrie-decembrie 1

DETERMINADETERMINADETERMINADETERMINATION OF THE TION OF THE TION OF THE TION OF THE SOLENASOLENASOLENASOLENATION OFTION OFTION OFTION OF EXCITAEXCITAEXCITAEXCITATIONTIONTIONTION OF A OF A OF A OF A SYNCHRONOUS GENERATOSYNCHRONOUS GENERATOSYNCHRONOUS GENERATOSYNCHRONOUS GENERATORSRSRSRS, , , , BY THE MATHEMATICS BY THE MATHEMATICS BY THE MATHEMATICS BY THE MATHEMATICS

METHODMETHODMETHODMETHOD

PhD, Prof. Eng. Ec. Ion PIROI, Lecturer PhD Student Eng. Elisabeta SPUNEI

University Eftimie Murgu from Reia

Faculty of Electrical Engineering and Informatics

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1. INTRODUCTION

In the category of renewable energy sources,

established by CE, is the electricity produced in the

MHC with less than 10 MW power [3].

The majority hydroelectric power plants are equipped

with synchronous generators. They must meet users requirements for power, speed, operating mode

(autonomous or connected to the network), but not

every time these requirements can be met by large

manufacturing companies, which typically have lower

limited power. This is the reason why the authors of this

paper have proposed optimal designing of a

synchronous generator, designed to equip a small

hydro. In doing this we faced with problems related to

the excitation winding.

In the case of a synchronous generator designing,

especially low-power, solenaion excitation at rated load has a significant importance. At low power

generators there is a risk of insufficient space for

winding excitation is.

2. DETERMINATION OF THE EXCITATION AT RATED LOAD BY GRAPHICAL METHOD

The solenaion excitation is determined after the

construction of the partial characteristics of the

synchronous generator, represented in Figure 1.

Fig. 1. The characteristics of the synchronous generator.

The partial magnetic characteristics are:

- the operation in no load, ( )HUf= ;

- of the stator, ( )1djHUf = ;

- of the rotor, ( )HrUf= ; - of the flow of dispersion between the poles,

( )1djH

Uf = .

The operation in no load characteristc, ( )HUf= , represents at a different scale, the characteristic

)( Ee IfU = .

Buletinul AGIR nr. 4/2012 octombrie-decembrie_____________________________________________________________________________________

47

NATIONAL CONFERENCE OF ELECTRICAL DRIVES CNAE 2012

Buletinul AGIR nr. 4/2012 octombrie-decembrie 2

For the representation of the characteristics, all voltages

and magnetic flux values are transformed into relative

units (ur), and in Figures 1 and 2 these are symbolized

with tilde.

FIG. 2. The constructions necessary for the determination solenation excitation at rated load.

The excitation solenation at rated load is determined

by graphics constructions related the high

characteristics and presented in Fig. 1., construction

that are presented in Fig. 2.

3. DETERMINATION OF THE EXCITATION SOLENATION AT RATED LOAD BY MATHEMATIC METHOD

Because of the errors which can occur in raising

construction related graphics, the graphic method is not

always an accurate method of showing the correct value

of excitation solenation.

To eliminate this inconvenience, we developed a

computer program using Mathcad software, through

which, the excitation solenation at rated load can be

determined more quickly and accurately.

Next well present in short the methods used to determine the analytical excitation solenation at rated

load. The graphs used below, are conceived by us.

The magnetic air gap voltage, U'H, in relative units, is the relation between the magnetic air gap voltage, UH, at load operation and the magnetic voltage of the

synchronous generator, UH0, at no load operation, that is:

0

H

H

H

UU

U

= [u.r.] (1)

Depending on the magnetic air gap voltage, the

corresponding flow, ' , in relative units is determined (see Fig. 3).

Knowing the operating power factor of the generator,

imposed by the designing theme, follows the angle in degree and r in radians.

With this value of the angle r, and knowing the resistance of the Indus phase, r1 [u.r.], is calculated the large side U1a, of the triangle, which is the other side U1

respectively r1, in relative units, Fig. 4., with the relation:

( )2 21 1 1 1 12 cosa rU U r U r = + [u.r.] (2)

Fig.3. The variation of voltage flow depending on the the magnetic

air gap.

I

U1

r1U1a

x1

E1

O

Eq0

D

o

E1d

F

B

Fig.4. Explanations necessary of application