Bai 5-Dong Co Khong Dong Bo Ba Pha

8/8/2019 Bai 5-Dong Co Khong Dong Bo Ba Pha

1/15

PHNG TH NGHIM K THUT IN

GIO TRNH THC TP K THUT IN 2 Trang 66

BI 5: NG CKHNG NG B BA PHA

PHN I: MC CH TH NGHIMWhen you have completed this exercise, you will be able to demonstrate

and explain the operation of three phase squirrel cage induction motor using the

squirrel- cage induction Motor module.

PHN II: TM TT L THUYTHnh 5-1 biu din mt nam chm di chuyn pha trn bn phi ca mt

nhm thanh dn. Cc thanh dn c ni ngn mch c dng hnh mt ci thang.

Hnh 5-1

Dng in chy trong vng dy to bi cc thanh dn 1 v 2, cng nhtrong vng dy to bi thanh dn 2 v 3. Cc dng in ny to ra t trng ccc nam v cc bc nh hnh 5-1.

Hnh 5-2


2/15



S tng tc gia t trng ca nam chm v t trng ca dng in chytrong ci thang to ra lc gia nam chm v thang. Lc ny lm cho thang chuynng theo chiu chuyn ng ca nam chm. Tuy nhin nu thang chuyn ng

cng tc vi nam chm, s khng c s bin thin t thng qua thang. Kt qul sc in ng cm ng trong thang bng zero, v dng in cm ng trit tiu,ngha l lc in t tc ng ln thang khng cn na. Do , thang chuyn ngchm li, nh hn tc nam chm. Lc ny lc in t li xut hin, ko thangchuyn ng theo nam chm. chnh lch vn tc gia nam chm v thang cngln, t thng xuyn qua khung dy bin i cng mnh v do lc in t tcng ln thang cng ln.

Rotor ca ng ccm ng khng ng b c to ra bng cch un congthang to thnh dng lng sc nhhnh 5-3. cng l ngun gc tn gi ng ckhng ng b rotor lng sc.

Hnh 5-3

t thng mc vng qua lng sc

c d dng, n

c lp trn mtkhi st t hnh tr c. Stator ca ng ccm ng hot ng nhmt nam chmin quay. S quay ca nam chm in to ra mmen ko rotor quay theo.

Mt trong nhng cch to ra nam chm in quay l ni ngun in ba phan ba cun dy stator A, B v C t lch nhau 120o nh hnh 5-4.

Hnh 5-4


3/15



Khi cc sng sin lch nhau 120o, nh hnh 5-5 chy qua ba cun dy statorA, B v C s to ra t trng quay theo chiu kim ng h nh hnh 5-6. Chngta thy rng cc ng sc t i ra cc bc v i vo cc nam.

Hnh 5-5

Dng in ba pha to ra t trng quay c ln khng thay i. Tc ca t trng quay c xem nh tc ng b, tc ny t l thun vi tn sca ngun in. Mt t trng quay c th nhn c bng cch kt ni cc sngsine lch pha vi nhau, nhng dng in ba pha c s dng thng dng nht.

Khi mt rotor lng sc c t bn trong mt t trng quay, n b kotheo chiu quay ca t trng. Nu thay i chiu ca 2 trong 3 dng in vo dyqun stator, t trng quay s i chiu dn n chiu quay ca rotor cng thayi.

Da vo nguyn l hot ng ca ng c khng ng b ta thy rngmmen do ng c sinh ra tng khi chnh lch tc gia vn tc ca ttrng quay v vn tc rto tng. chnh lch tc ny gi l trt. thbiu din mi quan h gia tc rto n v mmen T c cho trn hnh 5-7. Nhchng ta thy, tc rto lun nh hn tc ng b ns bi v trt s to rammen chc trn trc ng c.

c tuyn tc - mmen ca ng ckhng ng b rto lng sc tngt ng cDC kch t c lp. Tuy nhin, dng in cm ng trong lng sc phii chiu cng nhanh khi trt cng tng. Mt cch khc, tn s ca dng in

cm ng trong rto tng khi trt tng. V rto c to thnh t cun dy vli thp, nn tn ti cm khng trong mch dy qun rto. Do , cm khng ny

chng li s bin thin ca dng in. Kt qu l, dng in cm ng trong rtokhng tng t l thun vi trt ca ng c. iu ny nh hng n ctuyn tc - mmen nh hnh 5.81.


4/15



Hnh 5-8


5/15



Hnh 5-9

T c tuyn ta thy, vn tc khng ti hi nh hn vn tc ng b ns,nhng khi mmen ti tng, tc ng cgim. Tip tc tng ti, mmen ng ctng n khi mmen ng c t gi tr max, nu tip tc tng ti mmen ngc chng nhng khng tng m ngc li nhanh chng gim v gi tr mmen

kh

i

ng

ng th

i t

c

ng c

nhanh chng gim v

zero. Khi kh

i

ng,ng cc tc thp nhng dng khi ng rt ln v tiu th cng sut ln hn

ch vn hnh bnh thng.Mt c tnh khc ca ng c khng ng b ba pha l ng c lun s

dng cng sut phn khng t ngun in ac. Cng sut phn khng thm ch vtqu cng sut tc dng khi ng ckhng ng b vn hnh khng ti. Cng sutphn khng rt cn thit to ra t trng quay ging nh cun cm cn cngsut phn khng to t trng xung quanh cun dy.


6/15



PHN III: TRNH TTH NGHIM

I. NG CKHNG NG B BA PHA

1. Ci t ngun cung cp, ng c ko / lc k, ng c khng ng b ba pharotor lng sc 4 cc, v b giao tip thu thp d liu vo bn th nghim.

Ni c kh gia ng cko / lc k vi ng ckhng ng b rotor lng sc 4cc.

2. Chc chn rng cng tc ngun cung cp c t v tr O (OFF), v nmiu chnh in p vn ht mc ngc chiu kim ng h. Chc chn rng ngun

cung cp c ni vi ngun in 3 pha trn tng.

3. Chc chn rng dy cp t my tnh c ni vi DAI.Ni LOW POWER INPUT ca DAI v ng c ko/lc k ti ngun 24 V - ACca ngun cung cp. t cng tc ngun 24V - AC v v tr I (ON).

4. Mmn hnh ng dng Metering. Chn file ACMOTOR1.dai.

5. Ni mch nhhnh 5-10.

Hnh 5-10. ng ckhngng b rotor lng sc c ni vi lc k.

6. t cc thng s iu khin ng cko / lc k nh sau:MODE switch .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. DYN.

LOAD CONTROL MODE switch .. .. .. .. .. .MAN.

LOAD CONTROL knob .. .. .. .. .. .. .. .. .. .. .MIN. (fully CCW).

DISPLAY switch .. .. .. .. .. .. .. .. .. .. .. . .. .. TORQUE (T).

7. Mngun cung cp v vn nm iu chnh in p sao cho gi tr in p oc trn E1 bng gi tr in p dy bnh thng ca ng c khng ng b

rotor lng sc. (Gi tr in p nh mc ghi gc tri ca mi cm thit b).ng c quay theo chiu no?....................... ......................... ......................... ......................................................

T

N

E1

E2

I1

I2+

+

+

+

T

N

SQUIRREL

CAGE

INDUCTIONMOTOR

DYNAMOMETER

4

65


7/15



Ghi li s tc quay ca rotor?N = ------------- r/min.

ch khng ti, tc rotor bng tc t trng quay phi khng?Phi Khng

8. Trong ca s Metering, chc chn rng ng h mmen T ang chc nnghm Correction (C).

Trn ng cko / lc k, iu chnh nm LOAD CONTROL cng sutckh ( o c bng ng h Pm trn ca s Metering) ca ng cpht ra bng175 W (bng cng sut nh mc).

Ghi li tc nh mc, momen, v dng in dy (dng in dy o cbng ng h I1):NNOM = ----------r/min; TNOM = -----------N.m ; INOM = ------------A.

9. Trn mn hnh Metering hin th ng h o in p dy E1, dng in dy I1,cng sut tc dng C, cng sut phn khng A, tc N, v momen T.

Trn ng c ko / lc k, iu chnh nm LOAD CONTROL momen

tng t 0 N.m ln 3 N.m, mi b

c 0.1N.m. Sau mi gi tr momen, khi tc ng cn nh. Ghi s liu vo bng Data Table. (n khi tc ng cgimnhanh th lp tc tt ngun).

10. Khi tt c cc s liu c ghi. Tt ngun, chnh nm LOAD CONTROLtrn ng c ko / lc k v v tr nh nht (quay ht cngc chiu kim ngh), xoay nt iu ch nh in p ht cv pha ngc chiu kim ng h.Dng in dy I1 ca ng c tng khi ti ckh t ln ng c tng phi khng?

Phi Khng

11. Trong ca s Graph, v th biu din mi quan h gia tc ca ng cn

(thu t ng h N) l hm s ca momen T (thu c t ng h T). Trc X lmomen ng c, trc Y l tc ng c, v v li th vo ti liu ca bn.

MOTOR TORQUE (N.m)

M t ngn gn tc thay i nh th no khi ti c kh t vo ng c tngcng nhkhi momen tng.

....................... ......................... ......................... ......................................................

....................... ......................... ......................... ......................................................

MOTORSPEED(RPM)


8/15



12. Ch ra trn th vn tc nh mc v momen nh mc ca ng c.Xc nh momen cc i ca ng c.TMAX = ------------------N.m.

Xc nh momen khi ngTSTART = ------------------N.m.

So snh momen cc i v momen khi ng vi momen nh mc ca ng c................. ......................... ......................... .............................................................

................ ......................... ......................... .............................................................

................ ......................... ......................... .............................................................

13. Trong ca s Graph, v th cng sut tc dng P, cng sut phn khng Q(thu c t ng h C v ng h A tng ng) l hm s ca tc n (thu ct ng h N) dng bng s liu ghi t trc. Trc X l tc ng c, trc Yl cng sut tc dng v cng sut phn khng, v v li th vo ti liu cabn. th chng minh rng ng ckhng ng b rotor lng sc lun lun tiu th(draw) cng sut phn khng t ngun in xoay chiu phi khng?

Phi Khng

MOTOR SPEED (RPM)

th chng minh rng ng c khng ng b rotor lng sc tiu thnhiu cng sut in hn t ngun xoay chiu khi n phi ko ti nng hn phikhng?

Phi KhngQuan st khi ng c chy khng ti, cng sut phn khng ln hn cng

sut tc dng? Lc ny ng cging nhphn t no ca mch in xoay chiu?................ ......................... ......................... .............................................................

................ ......................... ......................... .............................................................

14. Trong ca s Graph, v th biu din mi lin hgia dng in dy ILINE(thu c t ng h I1) l hm s ca tc rotor n (thu c t ng h N)dng bng s liu ghi t trc. Trc X l tc ng c, trc Y l dng indy.

Dng in dy thay i nh th no khi tc rotor gim?................ ......................... ......................... .............................................................

................ ......................... ......................... .............................................................

ACTIVEANDREACTIVE

POWER


9/15



15. Dng in dy nh mc nh hn dng in dy lc khi ng (dng in dyo c khi tc ng c nh nht nh l dng in dy lc khi ng) bao

nhiu ln ?....................... ......................... ......................... ......................................................

....................... ......................... ......................... ......................................................

Chiu quay ca ng ckhng ng b

16. Trn ng c, thay i v tr 2 trong 3 u ni vo cun dy stator.Mngun in v t nm iu chnh in p sao cho in p dy ch bi ng hE1 gn bng gi tr in p nh mc ca ng c.

ng c quay theo chiu no?....................... ......................... ......................... ......................................................

ng cquay theo chiu ngc li so vi chiu ghi trong th nghim trc phikhng?

Phi Khng

17. Tt ngun cung cp, vn nm

iu chnh

in p hon ton v h

ngngc chiu kim ng h . t cng tc 24 V - AC v v tr O (OFF), nguyn mch.

nh Hng Ca in p Ln Cc c Tnh Lm Vic Ca ng C.

18. Mngun cung cp v t gi tr in p sao cho in p dy bng 75% inp nh mc ca cun dy.Ghi li tc ng c lc khng ti bng ng h N trong ca s Metering.

N = --------------- r/min (lc in p bng 75% in p nh mc).Tc thu c khi ng c chy vi in p bng 75% in p nh mc ln

hn hay nh hn tc ng c khi ng c chy vi in p bng in p nhmc nh lm bc 7........................ ......................... ......................... ......................................................

Khi thay i in p t vo ng c th tc ng c thay i phi khng?Phi Khng

19. Trong ca s Metering, xa cc s liu ghi trong Data Table. Hin th ccng h o E1, I1, C, A, N, T v chc chc rng ng h T c chn ch

correction(C).

Trn ng c ko / lc k, iu chnh nm LOAD CONTROL sao cho momentng t 0 N.m n khi tc ng c gim xung nhanh (breakdown torque

region). Mi bc 0.1N.m. mi gi tr momen t, ghi li s liu vo bngData Table.

Khi tc motorn nh, ghi li gi tr vo Data Table.

20. Khi tt c s liu c ghi, tt ngun cung cp, t nm LOADCONTROL ng c ko / lc k v v tr MIN (ht c ngc chiu kimng h), vn nt iu chnh in p hon ton v pha ngc chiu kim ngh.Trong ca s Data Table, chc chn rng tt c s liu c ghi.


10/15



Dng in dy I1 ca ng c tng khi ti ckh t ln ng c tng phi khng?Phi Khng

21. Trong ca s Graph, v th biu din mi quan h gia tc ng c n(thu c t ng h N) l hm s ca momen T(thu c t ng h T). Trc Xl momen ng c, trc Y l tc ng c, v v li th vo ti liu ca bn.

MOTOR TORQUE (N.m)

Xc nh momen cc i ca ng c.TMAX = ------------------N.m. (khi in p cung cp bng 75% in p nhmc).Xc nh momen khi ng ca ng cTSTART = ------------------N.m. (khi in p cung cp bng 75% in p nhmc).

So snh momen cc i, momen khi ng, moment nh mc ca ng c thu

c khi in p t vo ng c bng 75% in p nh mc vi cc momentng ng khi in p t vo bng 100% in p nh mc., nhbc 12 ................. ......................... ......................... .............................................................

................ .......................... ......................... ............................................................

................ ......................... ......................... .............................................................

Momen ng cgim khi in p t vo ng cgim phi khng?Phi Khng

22. Trong ca s Graph, v th biu din mi quan h gia cng sut tc dngP, cng sut phn khng Q (thu c tng ng t ng h C v A) l hm s catc ng cn (thu c t ng h N) dng s liu ghi c trong bng. Trc

X l tc ng c, trc Y l cng sut tc dng v cng sut phn khng, v vli th vo ti liu ca bn.

MOTORSPEED(RPM)


11/15



MOTOR SPEED (RPM)

So snh cng sut tc dng v cng sut phn khng thu c khi in p t vong cbng 75% in p nh mc vi cng sut tng ng thu c khi in pt vo ng cbng 100% in p nh mc, nhbc 13.

................ ......................... ......................... .............................................................

................ ......................... ......................... .............................................................

................ ......................... ......................... .............................................................

23. Trong ca s Graph, t cc trc thch hp thu c th dng in dyILINE (thu c t ng h I1) l hm s ca tc ng cn(thu c t ng hN) dng s liu ghi c t trc.Trc X l tc ng c, trc Y l dng in dy.

MOTOR SPEED( RPM)

So snh dng in khi ng (dng in dy ti lc tc chm nht) thu c

khi in p t vo ng cbng 75% in p nh mc, vi dng in khi ngtng ng thu c khi in p t vo ng c bng 100% in p nh mc.

................ ......................... ......................... .............................................................

................. ......................... ......................... ............................................................

................ ......................... ......................... .............................................................

in p t vo ng c gim s lm gim dng in khi ng phi khng?Phi Khng

24. t cng tc 24 V - AC v v tr O (OFF), v tho tt c cc dy dn.

MOTORLINECURRENT

(A)

ACTIVEANDREACTIVE

POWER


12/15



II. PHANH IN T

25. Lp mch in nhhnh 5.2, vi R gm ba in tr4400, 2200 1100 nisong song.

Hnh5-11

226. M ngun cung c p v iu chnh in p Prime Mover t tc 150rpm. Trn mn hnh Metering t ng h I1ch DC v bo m ng h

o mmen t ch correction (C). ng h T lc ny ch mmen hm gy rabi ng c khng ng b ba pha.

Ghi li tc n, dng in hm IEM, mmen hm v chiu quay:n = -------------------rpmIEM = ----------------A

TBRAKING = --------------Nm

Direction of Rotation:----------------------------------_________

27. Ln lt ng cc cng tc trn ti in tr tng gi tr dng in hm.Trong khi thao tc quan st tc v mmen trn mn hnh Metering.Khi tt c cc cng tc u ng, ghi li tc n, dng in hm IEM, mmen hmv chiu quay:

n = ---------------- rpm.

IEM =----------------A.

TBRAKING = ----------------Nm.Direction of Rotation:---------------------------________________

28. Tt ngun cung cp.M t quan h gia mmen hm v dng in hm IEM:

.....................................................................................................................................

................... ......................... ......................... ................................................................

................... .......................... ......................... ...............................................................

PRIME

MOVER

T

N

SQURREL

- CAGE

INDUCTON

MOTOR

I 1

R1


13/15



29. Trn ng c ko, hon i v tr hai u dy dn in vo ng c. Trn tiin tropen tt c cc cng tc R t gi tr v cng.

30. Mngun cung cp v iu ch nh in p tc ng c t 150rpm.Ghi li tc n, dng in hm IEM, mmen hm v chiu quay:

n = ----------------rpm

IEM = ----------------A

TBRAKING = ----------------Nm

Direction of Rotation: --------------------------------_

________________

31. Ln lt ng cc cng tc trn ti in tr tng gi tr dng in hm.Trong khi thao tc quan st tc v mmen trn mn hnh Metering.Khi tt c cc cng tc u ng, ghi li tc n, dng in hm IEM, mmen hmv chiu quay:

n = ----------------rpm

IEM = ----------------A

TBRAKING = ----------------Nm

Direction of Rotation: --------------------------------_________________

32. Tt ngun cung cp.M t quan h gia mmen hm v dng in hm IEM:

.....................................................................................................................................

................... ......................... ......................... ................................................................

................... ......................... ......................... ................................................................

S hot ng ca ng ckhng ng b bnh hng bi chiu quay ca PrimeMover phi khng?

Phi Khng

III. MY PHT KHNG NG B BA PHA

33. Lp mch nhhnh 5-12, nhng khng ni ba im A, B v C vo ngun inba pha.

Hnh:5-12

2. Mngun cung cp v iu chnh in p sao cho ng cko quay cng chiukim ng h t tc 1200 rpm.

Hnh 5-12

33. Tt ngun cung cp, nhng khng thay i nm iu chnh in p.


14/15



34. Ni ba im A, B v C vo ngun in ba pha 4-5-6 nhhnh 5-12.t cc thng s iu khin nh sau:

MODE switch............................DYN

LOAD CONTROL MODE switchMAN

LOAD CONTROL knobMIN

DISPLAY switch...............TORQUE

35. Mngun cung cp v bo m ng c quay cng chiu kim ng h.

36. Trn ng c ko iu chnh nm LOAD CONTROL mmen ch trn mnhnh t gi tr 1.0Nm.

Ghi li cc gi tr sau:P = W. Q =vars.

Pm =W. n = rpm.

T =Nm.

C phi cng sut tc dng i t ngun ac n ng c khng ng b ba phakhng?

Phi KhngLc ny ng cging nh phn t no ca mch in xoay chiu?.............................................................................................................................

37. Trn ng c ko vn nm LOAD CONTROL v v tr MIN v t cng tcMODE v v tr PRIME MOVER. Trong khi thao tc, quan st cng sut tc dngP, cng sut phn khng, cng sut ckh Pm.

38. Trn Power supply, vn nm iu chnh in p cho n khi ng c t titc ng b. Ghi li cc gi tr sau:

P = W. Q = vars.

Pm =W. n = rpm.

T =

Nm.C phi c s trao i cng sut tc dng gia ngun v ng ckhng ng bphi khng?

Phi Khng

39. Trn Power supply, vn nm iu chnh in p cho n khi ng c t ti105% tc ng b. Ghi li cc gi tr sau:

P = W Q = vars

Pm =W n = rpm

T =Nm

C phi cng sut tc dng i t ng ckhng ng b ba pha n ngun in ac

khng?Phi Khng

Lc ny ng cging nh phn t no ca mch in xoay chiu?---------------------------------------------------------------------------------------

40. Tt ngun cung cp v vn nm iu chnh in p v zero.Tho cc im A, B v C ra khi ngun in ba pha. Mngun cung cp v iuchnh in p Prime Mover t tc 1000 rpm.

Ghi li gi tr in p sinh ra bi my pht khng ng b ( ng h E1).


15/15



ELINE =V

Gi tr in p ny cho thy my pht khng ng b khng th vn hnh cnu n khng c ni n ngun in ac ba pha phi khng?

Phi Khng

41. Tt ngun cung cp v vn nm iu chnh in p v zero.

PHN IV: KT LUNYou observed that when the nominal line voltage is applied to the stator

windings of a squirrel-cage induction motor without mechanical load, the rotor

turns at approximately the same speed as the rotating magnetic field (synchronous

speed). You saw that interchanging any two of the three leads supplying power to

the stator windings reserves the phase sequence, and thereby, causes the motor to

rotate in the opposite direction. You observed that the motor line currents increase

as the mechanical load increases, thus showing that the squirrel -cage induction

motor requires more electric power to drive heavier loads. You plotted a graph of

speed versus torque and used it to determine the nominal, breakdown, and locked -

rotor torques of the squirrel -cage induction motor. You also plotted a graph of themotor reactive power versus speed and observe that the squirrel cage induction

motor draws reactive power from the ac power source to createits magnetic field.

Finally, you plotted a graph of the motor line current versus speed and observed

that the starting current is many times greater than the nominal line current.

Documents

Bai 5-Dong Co Khong Dong Bo Ba Pha