Çàäà÷è ïîâûøåííîé ñëîæíîñòè

ÇÀÄÀ×À 3.60. Íàéòè ïîêàçàíèå âàòòìåòðà ñõåìû ðèñ. 3.60, åñëè J = 10 A,

r1 = r2 =10 Îì, x1 = 20 Îì, x2 =10 Îì,

xM =10 Îì, x3 = 20 Îì, x4 =10 Îì.

Îòâåò: PW = 2000.

 

ÇÀÄÀ×À3.61.  ñõåìå ðèñ. 3.61

u(t) = 120 sin(wt+45°) B, r1 = r2 = xC = 60 Îì, xL = 40 Îì, xM = 20 Îì.

Îïðåäåëèòü ìãíîâåííîå è äåéñòâóþùåå çíà÷åíèå òîêà i1.

Îòâåò: i1(t ) = 2×sin(wt) A, I1= A.

 

ÇÀÄÀ×À 3.62. Ìîñòîâàÿ ñõåìà ðèñ. 3.62,à ïèòàåòñÿ îò èñòî÷íèêà ñèíóñîèäàëüíîãî íàïðÿæåíèÿ ñ äåéñòâóþùèì çíà÷åíèåì Å = 300 B.

Ïàðàìåòðû ñõåìû: r1 =10 Îì, x1 =15 Îì, r2 = 30 Îì, x2 = 20 Îì,

xM12 =13 Îì, x3 = 25 Îì, r4 =16 Îì, x5 = 40 Îì, x6 =12 Îì.

Èñïîëüçóÿ òîïîëîãè÷åñêèå ìàòðèöû, ñôîðìèðîâàòü ñèñòåìó ðàñ÷¸òíûõ óðàâíåíèé äëÿ îïðåäåëåíèÿ òîêîâ ðàçëè÷íûìè ìåòîäàìè:

1) ìåòîäîì óðàâíåíèé Êèðõãîôà;

2) ìåòîäîì êîíòóðíûõ òîêîâ;

3) ìåòîäîì óçëîâûõ ïîòåíöèàëîâ.

Ðàññ÷èòàòü òîêè è ïðîâåðèòü áàëàíñû ìîùíîñòåé.

Ðåøåíèå

Âûáèðàåì ïðîèçâîëüíûå íàïðàâëåíèÿ òîêîâ â âåòâÿõ ñõåìû (óêàçàíû íà ðèñ. 3.62,à) è ñòðîèì ãðàô ýëåêòðè÷åñêîé öåïè òàêîé, ÷òîáû èíäóêòèâíî ñâÿçàííûå âåòâè (ïåðâàÿ è âòîðàÿ) áûëè âåòâÿìè ñâÿçè. Òàêîé ãðàô ïðèâåäåí íà ðèñ. 3.62,á, â êîòîðîì âåòâè ¹ 3, 4, 5 ÿâëÿþòñÿ âåòâÿìè äåðåâà.

Ïðèìåì êîìïëåêñ Å = Å = 300 B. Êîìïëåêñíûå ñîïðîòèâëåíèÿ âåòâåé ñõåìû: Z1 = r1 + jx1= 10 + j15 Îì, Z2 = r2 + jx2 = 30 + j20 Îì,

ZM12 = jxM12 = j13 Îì, Z3 = –jx3= –j25 Îì,

Z4 = r4 = 16 Îì, Z5 = jx5= j40 Îì, Z6 = jx6= j12 Îì.

Ñîñòàâèì ìàòðèöû:

- óçëîâàÿ ìàòðèöà ñîåäèíåíèé âåòâåé ïðè áàçèñíîì óçëå ¹4, ïîòåíöèàë êîòîðîãî j 4 = 0,

[A]= ;

- ìàòðèöà ãëàâíûõ êîíòóðîâ [B]= ;

- ìàòðèöà ñîïðîòèâëåíèé âåòâåé [Zâ]= ;

- ñòîëáöîâàÿ ìàòðèöà ÝÄÑ âåòâåé [Eâ]= ;

- ñòîëáöîâàÿ ìàòðèöà òîêîâ èñòî÷íèêîâ òîêîâ âåòâåé

[Jâ]= ;

- ñòîëáöîâàÿ ìàòðèöà íåèçâåñòíûõ òîêîâ âåòâåé

[Iâ]= ;

- ñòîëáöîâàÿ ìàòðèöà íàïðÿæåíèé âåòâåé

[Uâ]= ;

- ñòîëáöîâàÿ ìàòðèöà êîíòóðíûõ òîêîâ (èëè òîêîâ âåòâåé ñâÿçè)

[Ik]= [Ic]= ;

- ñòîëáöîâàÿ ìàòðèöà ïîòåíöèàëîâ óçëîâ [j]= .

 
 

Óðàâíåíèÿ Êèðõãîôà

Ïî ïåðâîìó çàêîíó Êèðõãîôà [A]×[Iâ]=[0]. Ïîñëå ïåðåìíîæåíèÿ ìàòðèö ñèñòåìó óðàâíåíèé ïîëó÷àåì â ðàçâ¸ðíóòîì âèäå

I1 + I3 I6 = 0;

-I1 + I4 + I5 = 0; (1)

-I2 I4 + I6 = 0.

Äëÿ çàïèñè ñèñòåìû óðàâíåíèé ïî âòîðîìó çàêîíó Êèðõãîôà èñïîëüçóåì ñëåäóþùóþ ðåäàêöèþ ýòîãî çàêîíà:

[B]×[Zâ]×[Iâ] = [B]×{[Eâ] - [Zâ]×[Jâ]}.

Ïîñëå ïåðåìíîæåíèÿ ìàòðèö ïîëó÷àåì ðàçâ¸ðíóòóþ ñèñòåìó óðàâíåíèé, ñîñòàâëåííóþ äëÿ èññëåäóåìîé ñõåìû ïî âòîðîìó çàêîíó Êèðõãîôà: Z1×I1+ ZM12×I2 Z3×I3 + Z5×I5= 0;

ZM12×I1+ Z2×I2 Z4×I4+ Z5×I5= 0; (2)

Z3×I3+ Z4×I4 Z5×I5+ Z6×I6= E.

Îòìåòèì, ÷òî ñèñòåìà øåñòè óðàâíåíèé (ñèñòåìà (1) + ñèñòåìà (2)) ëåãêî ñîñòàâëÿåòñÿ ïî ñõåìå áåç ïðèìåíåíèÿ ìàòðèö.

 

Êîíòóðíûå óðàâíåíèÿ

 ìàòðè÷íîé ôîðìå êîíòóðíîå óðàâíåíèå èìååò âèä [Zk]×[Ik] = [Ek], ãäå êîíòóðíûå ÝÄÑ [Ek] = [B]×{[Eâ] - [Zâ]×[Jâ]} ïðåäñòàâëÿþò òó æå ñòîëáöîâóþ ìàòðèöó, êîòîðàÿ ïðèâåäåíà â ñèñòåìå (2) óðàâíåíèé, çàïèñàííûõ ïî âòîðîìó çàêîíó Êèðõãîôà.

Ðàññ÷èòàåì ìàòðèöó êîíòóðíûõ ñîïðîòèâëåíèé [Zk] = [B]×[Zâ]×[B]T

ïóò¸ì ïåðåìíîæåíèÿ ìàòðèö. Ïîëó÷àåì ñèììåòðè÷íóþ îòíîñèòåëüíî ãëàâíîé äèàãîíàëè ìàòðèöó

[Zk] = .

Ñèñòåìà êîíòóðíûõ óðàâíåíèé â ðàçâ¸ðíóòîì âèäå ïðåäñòàâëÿåòñÿ ñèñòåìîé (3):

(Z1+Z3+Z5)×I1+ (ZM12+Z5)×I2 (Z3+Z5)×I6 = 0;

(ZM12+Z5)×I1+ (Z2+Z4+Z5)×I2 (Z4+Z5)×I6 = 0; (3)

-(Z3+Z5)×I1 (Z4+Z5)×I2+ (Z3+Z4+Z5+Z6)×I6= E.

Îòìåòèì, ÷òî ýòà ñèñòåìà òàêæå ìîæåò áûòü ëåãêî ñîñòàâëåíà ïî èñõîäíîé ñõåìå áåç ïðèìåíåíèÿ ìàòðèö.

 

Óçëîâûå óðàâíåíèÿ

 ìàòðè÷íîé ôîðìå óçëîâûå óðàâíåíèÿ ïðåäñòàâëÿþòñÿ ñîîòíîøåíèåì

[Yy]×[j] = [Jy],

ìàòðèöà óçëîâûõ òîêîâ [Jy] = [A]×{[Jâ] - [Yâ]×[Eâ]},

ìàòðèöà ïðîâîäèìîñòåé âåòâåé [Yâ]= [Zâ]-1,

ìàòðèöà óçëîâûõ ïðîâîäèìîñòåé [Yy] = [A]×[Yâ]×[A]T.

Ðàññ÷èòàåì ìàòðèöó ïðîâîäèìîñòåé âåòâåé äëÿ ðàññìàòðèâàåìîãî ïðèìåðà è îáðàòíóþ ìàòðèöó ñîïðîòèâëåíèé âåòâåé, ïðè ýòîì ãëàâíûé îïðåäåëèòåëü ìàòðèöû ñîïðîòèâëåíèé âåòâåé D = (Z1×Z2-ZM122)Z3Z4Z5Z6, à ìàòðèöà

[Yâ]= × ,

ãäå Aij – àëãåáðàè÷åñêèå äîïîëíåíèÿ ìàòðèöû [Zâ].  ðåçóëüòàòå ïîëó÷àåì

[Yâ]= .

Íàõîäèì ìàòðèöó óçëîâûõ òîêîâ [Jy] = -[A]×[Yâ]×[Eâ]= .

Ðàññ÷èòàåì ìàòðèöó óçëîâûõ ïðîâîäèìîñòåé

[Yy] = [A]×[Yâ]×[A]T=

= .

 

 ðàçâ¸ðíóòîì âèäå ñèñòåìà óçëîâûõ óðàâíåíèé ïðåäñòàâëÿåò ñèñòåìó (4):

j 1× j 2× j 3× = ;

-j 1× + j 2× j 3× = 0;

-j 1× j 2× +

+ j 3× = - . (4)

Î÷åâèäíî, ÷òî ýòó ñèñòåìó óðàâíåíèé âðó÷íóþ (áåç ìàòðèö) ïî èñõîäíîé ñõåìå ñîñòàâèòü íåâîçìîæíî.

Äëÿ ïðèâåäåííîé ìîñòîâîé ñõåìû êîíòóðíûå óðàâíåíèÿ (3) è óçëîâûå óðàâíåíèÿ (4) âêëþ÷àþò ïî òðè óðàâíåíèÿ è òðåáóþò îäèíàêîâîãî îáú¸ìà ðàáîòû äëÿ èõ ðåøåíèÿ.

Ðåøåíèå êîíòóðíûõ óðàâíåíèé (3), êîòîðûå ïîñëå ïîäñòàíîâêè ÷èñåë ïðåäñòàâëÿþòñÿ ñèñòåìîé

(10+j30)×I1+ j53×I2 j15×I6 = 0;

j53×I1+ (46+j60)×I2 (16+j40)×I6 = 0; (5)

-j15×I1 (16+j40)×I2+ (16+j27)×I6= 300,

ñëåäóþùåå I1= 0,073 – j7,496 A, I2= 5,103 + j2,219 A, I6= 13,18 – j7,2 A.

Òîêè âåòâåé ðàññ÷èòûâàåì ïî ïîëó÷åííûì êîíòóðíûì:

I1= 0,073 – j7,496 = 7,496×e –j89,44° A,

I2= 5,103 + j2,219 = 5,565×e j23,5° A,

I3= I6- I1= 13,11 + j0,296 = 13,12×e j1,29° A,

I4= I6I2= 8,08 – j9,22 = 12,41×e –j48,77° A,

I5= I1+ I2I6= -8 + j1,923 = 8,235×e j166,5° A,

I6= 13,18 – j7,2 = 8,23×e -j28,65° A.

Ïðîâåðèì áàëàíñû ìîùíîñòåé.

Ìîùíîñòü èñòî÷íèêà ïèòàíèÿ

S = Å× = Pà + jQà = 300×(13,18 + j7,2) = 3954 + j2160 BA.

Àêòèâíàÿ ìîùíîñòü ïðè¸ìíèêîâ

Ï = I12×r1 + I22×r2 + I42×r4 = 7,4962×10 + 5,5652×30 + 13,112×16 = 4241 Âò.

Ðåàêòèâíàÿ ìîùíîñòü ïðè¸ìíèêîâ

SQÏ = I12×x1 + I22×x2 - I32×x3 + I52×x5 + I62×x6 + 2×Im(I1× ×jxM) =

= 7,4962×15 + 5,5652×20 – 13,122×25 + 12,262×40 + 8,232×12 +

+ 2×7,496×5,565×13×sin(-84,44° – 23,5°+90°) = 2225 âàð.

Îòíîñèòåëüíàÿ ïîãðåøíîñòü ðàñ÷¸òîâ ïî àêòèâíîé (e1) è ðåàêòèâíîé (e2) ìîùíîñòÿì:

e1%= = 3,5% < 5%, e2%= = 1,48% < 5%.

Ðåçóëüòàò ðàñ÷¸òà ïðèåìëåìûé.

 








Äàòà äîáàâëåíèÿ: 2016-01-18; ïðîñìîòðîâ: 749;


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