Phan tich mach_dien_8783

  • Published on
    17-Jul-2015

  • View
    103

  • Download
    2

Embed Size (px)

Transcript

  • SCH

    CC PHNG PHP C BN PHN TCH MCH

    IN

  • CHNG 1CC KHI NIM, NH LUT V CC PHNG

    PHP C BN PHN TCH MCH IN

  • Ng c Thin - PTIT Chng 1 2

    Ni dung

    1. Tng quan2. Cc thng s tc ng v th ng3. Biu din phc cc tc ng iu ha. Tr khng v dn np4. Cc khi nim c bn ca mch in5. Cc nh lut KIRCHHOFF6. Mt s phng php phn tch mch in.

  • Ng c Thin - PTIT Chng 1 3

    1. Tng quan (1) S to ra, thu nhn v x l tn hiu l nhng qu trnh phc tp xy ra trong

    cc thit b & h thng khc nhau. Vic phn tch v l thuyt s c tin hnh thng qua cc loi m hnh gi l mch in.

    Tn hiu l dng biu hin vt l ca thng tin, n qui nh tnh cht v kt cu ca cc h thng mch. V mt ton hc, tn hiu c biu din bi hm ca cc bin c lp S(x,y,...).

    sa(t)

    t

    Analog signal

    t =

    ss(n.Ts)Discrete signal

    Tssq(t)

    t

    Quantizing signal

    n

    sd(n)

    Digital signal

  • Ng c Thin - PTIT Chng 1 4

    1. Tng quan (2) Cc ngun tn hiu trong t nhin c biu din theo nhiu dng khc nhau,

    v d: m thanh, hnh nh, chuyn ng c hc... x l hoc lu tr cc tn hiu ngi ta thng chuyn i chng

    thnh tn hiu in - tn hiu tng t (in p hoc dng in) thng qua Sensor, detector, or transducer.

    M hnh x l hai loi tn hiu

    ADC: Analog to Digital ConverterDAC: Digital to Analog Converter

    Mch x l tn hiu tng t

    Tn hiu s

    DACADCMch x ltn hiu s

    Tn hiu tng t

  • Ng c Thin - PTIT Chng 1 5

    2. Cc thng s tc ng v th ng ca mch in (1)

    2.1. Cc thng s tc ng ca mch in. Thng s tc ng cn gi l thng s to ngun. l cc thng s

    c trng cho tnh cht to ra tn hiu v cung cp nng lng ca cc phn t mch in. Thng s c trng cho ngun c th l:

    Sc in ng ca ngun: mt i lng vt l c gi tr l in p hmch ca ngun, o bng n v vn v c k hiu l V.

    Dng in ca ngun: mt i lng vt l c gi tr l dng in ngn mch ca ngun, o bng n v ampe v c k hiu l A.

    Cc k hiu ngun

    c) Ngun p ph thuc

    Eng

    +

    _

    Ing

    +

    _

    d) Ngun dng ph thuc

    Ing

    +

    _

    a) Ngun p c lp

    Eng+Eng

    +

    _Ing

    +

    _

    b) Ngun dng c lp

    Ing

    +

    _

  • Ng c Thin - PTIT Chng 1 6

    2. Cc thng s tc ng v th ng ca mch in (2)

    Ngun in l tng l khng c tn hao nng lng. Nhng trong thc t phi tnh n tn hao, c ngha l tn ti in tr trong ca ngun Rn.

    ngab t

    n t

    EU R

    R R

    Eng

    Rn

    a

    Rt

    b

    +

    Uab

    ngt n

    n t

    II R

    R R

    Ing Rn

    It

    a

    Rt

    b

    Yu cu: + Vi ngun p Rn nh (Uab Eng)+ Vi ngun dng: Rn ln (It Ing)

  • Ng c Thin - PTIT Chng 1 7

    2. Cc thng s tc ng v th ng ca mch in (3)

    2.2. Cc thng s th ng ca mch in.

    Trong p(t) =u(t).i(t) l cng sut tc thi. Nu u(t) v i(t) ngc chiu th p(t) c gi tr m phn t cung cp

    nng lng, ngha l phn t c tnh cht tch cc (v d ngun). Nu u(t) v i(t) cng chiu th p(t) c gi tr dng, vy ti thi im

    phn t nhn nng lng, ngha l phn t c tnh cht th ng. c trng cho s tiu tn v tch lu nng lng l cc thng s th

    ng ca phn t.

    2 2

    1 1( ) ( ) ( )

    t tT t t

    W p t dt u t i t dt Phn t

    i(t)

    u(t) Phn t

    i(t)

    u(t)

  • Ng c Thin - PTIT Chng 1 8

    2. Cc thng s tc ng v th ng ca mch in (4)

    2.2. Cc thng s th ng ca mch in.a. Thng s khng qun tnh (R).

    Thng s khng qun tnh c trng cho tnh cht ca phn t khi in p v dng in trn n t l trc tip vi nhau. N c gi l in tr (R), R l mt s thc, v xc nh theo cng thc:

    + G = 1/R gi l in dn, c n v l 1/ hay S (Siemen).+ V mt thi gian, dng in v in p trn phn t thun tr l

    trng pha nn nng lng nhn c trn phn t thun tr lun lun dng, v vy R c trng cho s tiu tn nng lng.

    1( ) . ( ) ( ) ( ) . ( )u t R i t hay i t u t G u t

    R

    u(t)

    i(t) R

  • Ng c Thin - PTIT Chng 1 9

    b. Thng s c qun tnh. Thng s in dung (C) c trng cho tnh cht ca phn t khi dng in

    chy trn n t l vi tc bin thin ca in p, c xc nh theo cng thc:

    [C] = F (fara).

    Nng lng tch lu trn C:

    - Xt v mt nng lng, thng s C c trng cho s tch lu nng lng in trng.- Xt v mt thi gian in p trn phn t thun dung chm pha so

    vi dng in mt gc /2.

    2. Cc thng s tc ng v th ng ca mch in (5)

    0

    ( ) 1 ( )( ) hay ( ) ( )

    tdu t q t

    i t C u t i t dtdt C C

    u(t)

    i(t) C

    21( ) . . ( ).2E

    duW p t dt C u t dt Cu

    dt

  • Ng c Thin - PTIT Chng 1 10

    b. Thng s c qun tnh. Thng s in cm (L) c trng cho tnh cht ca phn t m in p trn

    n t l vi tc bin thin ca dng in:

    [L] = H (Henry).

    Nng lng tch lu trn L:

    - Xt v mt nng lng, thng s L c trng cho s tch lu nng lng t trng. - Xt v mt thi gian, in p trn phn t thun cm nhanh pha so

    vi dng in l /2.

    2. Cc thng s tc ng v th ng ca mch in (6)

    u(t)

    i (t) L 0

    ( ) 1( ) hay

    tdi t

    u t L i t u t dtdt L

    212H

    diW L i t dt Li

    dt

  • Ng c Thin - PTIT Chng 1 11

    b. Thng s c qun tnh. Thng s h cm (M) c cng bn cht vt l vi thng s in cm, c

    trng cho s nh hng qua li ca hai phn t t gn nhau, ni hoc khng ni v in, khi c dng in chy trong chng:

    Trong , nu cc dng in cng chy vo hoc cng chy ra khi u c nh du * (u cng tn) th cc biu thc trn ly du +, nu ngc li ly du .

    2. Cc thng s tc ng v th ng ca mch in (7)

    i1M

    i2

    u1 u2L22L11

    **

    121 21

    diu M

    dt 212 12

    diu M

    dt

    1 21 11 12

    di diu L M

    dt dt

    1 22 21 22

    di diu M L

    dt dt

  • Ng c Thin - PTIT Chng 1 12

    Quan h v pha gia dng in v in p trn cc phn t R, L, C

    c. Thng s ca cc phn t mc ni tip v song songKhi c k phn t mc ni tip hoc song song

    2. Cc thng s tc ng v th ng ca mch in (8)

    LU

    RU

    I

    CU

  • Ng c Thin - PTIT Chng 1 13

    2.3. c tuyn in p Dng in (c tuyn V-A) c tuyn in p dng in (hay cn gi l c tuyn V-A) ca mt phn

    t mch in m t mi quan h gia dng in chy qua phn t v in p ri trn n.

    th c tuyn V-A ca mt cu kin v tt c cc im lm vic ca cu kin .

    V d mt in tr c c tuyn V-A theo nh lut Ohm l: i = u/R. dc ca c tuyn tnh c nh sau:

    V d vi in tr R = 10k, dc ca c tuyn l 0,1 mA/V

    2. Cc thng s tc ng v th ng ca mch in (9)

    1di

    du R

    2 4 u (V)

    i (mA)

    -4 -2-0,2

    -0,6

    -0,4

    -0,8

    0,8

    0,4

    0,6

    0,2

    dc = 0,1 mA/V

  • Ng c Thin - PTIT Chng 1 14

    2. Cc thng s tc ng v th ng ca mch in (10)

    V d 1.1.V c tuyn V-A cho hai im X-X dng ix chy t X n X. Khi c mt phn t ni vo hai im (v d mt in tr c gi trtrong khong 0 < RL < ).

    GiiTa thy ux = Eng uR1 = Eng ixR1

    dc ca c tuyn l:

    111

    1

    R

    Eu

    RR

    uEi ngx

    xngx

    1

    1

    Rdu

    di

    x

    x 2 4 ux (V)

    ix (mA)

    -4 -2-2

    6

    4

    2

    c tuyn V-A ca hai u X X

    6-6

    1

    5ngE

    mAR

    5ngE V

    +

    Eng 5 V

    1 1R k

    xi

    X

    X

    +

    xu

  • Ng c Thin - PTIT Chng 1 15

    2. Cc thng s tc ng v th ng ca mch in (11)

    Bi tp 1.1Trn cng mt h trc ta , v c tuyn V-A ca cc in tr c gi tr: 1k, 5k v 20.

    Hnh B1.1

    +

    Eng

    1R

    xi

    X

    X

    +

    xu

    Bi tp 1.2V c tuyn V-A cho hai im X-X trn hnh B1.1 khi R1 = 10k, Eng = 5V.

    Bi tp 1.3V c tuyn V-A cho hai im X-X trn hnh B1.1 khi R1 = 1k, Eng = 10V.

  • Ng c Thin - PTIT Chng 1 16

    3.1. Cch biu din phc cc tc ng iu ho1.3.1. Cch biu din phc cc tc ng iu hoXt cch biu din phc t cng thc Euler:

    Khi c mt dao ng iu ha, v d sc in ng:

    Ta c th vit:Vi

    Thng thng bin phc c tnh theo bin hiu dng:

    3. Biu din phc cc tc ng iu ha, tr khng & dn np (1)

    Em

    e(t)

    t

    T

    cos sinje j

    ( ) cos( )m ue t E t

    ( )E uj t j j tm mE e E e e &

    ( ) ReEe t &

    E ujm mE e&

    2mEE

    V d: in p

    Dng phc s l: 220 2 cos 60ou t

    0( 60 )220U j te &

  • Ng c Thin - PTIT Chng 1 17

    3. Biu din phc cc tc ng iu ha, tr khng & dn np (2)

    3.1. Cch biu din phc cc tc ng iu ho (tt) Vic biu din tn hiu tun hon theo dng phc rt thun li khi ta

    chuyn cc phng trnh vi phn, tch phn min thi gian sang cc phng trnh i s min tn s.

    Xt tn hiu tun hon u(t) = UMcos(t), biu din dng phc ca n:

    Vi php o hm:

    Vi php tch phn:

    Hay ni cch khc:

    tjM eU

    U

    dUU

    dtj t

    Mj U e j

    &&

    1 1U Uj tMdt U ej j

    & &

    Udu

    jdt

    &1

    Uudtj

    &

  • Ng c Thin - PTIT Chng 1 18

    3.2. Tr khng v dn np Trong mt mch in, thng s ca cc phn t xc nh mi quan h gia

    in p t trn v dng in chy qua chng. C th coi mch in thc hin mt ton t p vi cc hm tn hiu tc ng

    ln n, ton t thc hin s bin i in p dng in hay ngc li.

    3. Biu din phc cc tc ng iu ha, tr khng & dn np (3)

    px(t) y(t)=p{x(t)}+ Trong trng hp bin i

    dng in in p, ton t gi l tr khng Z ca mch:

    + Trng hp bin i in p dng in, ton t gi l dn np Y

    .U Z I& &

    1I U = YU

    Z& & &

    arg ( )ZZ Z jR jX e

    arg YY Y (S)jG jB e 1

    S =

  • Ng c Thin - PTIT Chng 1 19

    3.2. Tr khng v dn np (tt)

    3. Biu din phc cc tc ng iu ha, tr khng & dn np (4)

    ( )( )

    ( )

    UZ=

    I

    uu i

    i

    j tj

    j t

    Ue Ue

    IIe

    &

    &

    2 2ZU

    R XI

    arg ZZ

    Xarctg u iR

    ( )( )

    ( )

    I

    UY=

    ii u

    u

    j tj

    j t

    Ie

    UUe

    Ie

    &

    &

    2 2YI

    G BU