may dien robot long

CHO MNG NGY NH GIO VIT NAM 20/11/2012

Tp ch Khoa hc Cng ngh Hng hi S 32 11/2012

40

MY IN ROTOR LNG SC CH MY PHT THE CAGE ROTOR INDUCTION MACHINE WORKS IN GENERATOR MODE

TS. O MINH QUN Khoa in TTB, Trng HHH

Tm tt Bi bo gii thiu v my in khng ng b rotor lng sc lm vic ch my pht khi c lai bi ng c s cp c n nh tc , so snh cc u nhc im so vi my pht in ng b.

Abstrast This paper introduces the cage rotor induction machine in generator mode which is driven by the primary mover at stabilized speed, advantages and disadvantages compared to the synchronous generator (SA). Keyword: capacitor, generator, asynchronous

1. Gii thiu chung Theo nh lut Len x my in khng ng b c th hot ng nh mt ng c hoc

my pht in (asynchronous generator - AG). T ch ng c chuyn sang ch my pht th nng lng c tr v ngun, pha stator my in c ni vo mng, pha rotor c truyn ng bi ng c s cp lai (c th l tuabin nhit, ng c thy lc, ng c DC, ng c diezel hay tuabin gi), trong trng hp ny n c kt ni vi trc ca my in khng ng b v rotor ca n quay theo hng quay ca t trng tc n2 vt qu tc quay ca t trng quay n1, trt ca my in s m [2]:

)(1

21

nnns (1.1)

V mt l thuyt, tc quay ca rotor ch my pht in c th thay i khc nhau t

12 nn n khng gii hn, tng ng vi s thay i ca trt t s = 0 n s = - . Nhng trong thc t ch lm vic ca my pht in xy ra ph thuc vo ng c s cp v c cc gi tr ca trt tng ng nh ch ng c, ngha l s 68%.

Vic phn tch v so snh u nhc im my in khng ng b hot ng ch my pht c lp t kch cn c trnh by trong bi ny.

2. So snh my pht in khng ng b v my pht ng b u im hng u l

trng lng my pht in khng ng b nh hn nhiu so vi cc my pht in ng b [3]. Do my pht khng ng b c khong cch khe kh nh hn my pht ng b, cc thanh rut lng sc khng yu cu cch ly v c d dng lp t hn trn rotor so vi cc cun dy kch t. iu kin lm mt ca cun dy kch t my pht ng b th km hn so vi rotor lng sc ngn mch. Trn hnh 1, s dng hai my in c lm thc nghim, cng sut 20 KVA thy rng khi lng ca my khng ng b nh hn t 1,31,4 ln so vi my pht ng b. Nu so snh vi my pht in ng b khng chi than, khi lng my khng ng b nh hn khong 2 n 3 ln .

Hnh 1. Hai my pht c cng sut tng ng l 20 KVA.

a) my pht ng b, b) my pht d b



41

Tuy nhin, vic so snh cc my pht in khi xt n phn kch t, cho thy khi lng v chi ph ca t in trong mt s trng hp cao hn ng k so vi phn kch t my ng b. T in phi cung cp cho my pht in khng ng b dng t ha hin nay l bng 2535% dng nh mc cho cc ng c cng sut ln v ln n 70% cho ng c cng sut nh hn 1kW. Bn cnh vic cung cp nng lng kch t, cc t in cn phi b ti cm khng cho cc ph ti ca my pht.

tng minh trn hnh 2. biu din mi quan h gia M/P (khi lng/cng sut) v P (cng sut) (kg/kw v kw) ca my pht in ng b v khng ng b [4].

Hnh 2. Mi quan h gia khi lng ca my ng b v khng ng b vi cng sut tc dng P:

1, 2 - my pht in ng b v khng ng b m khng c thit b kch t; 3, 4 - my pht in ng b v khng ng b m c thit b kch t tn s 50 Hz v 3000 v/p;

5. 6 - my pht in ng b v khng ng b m c thit b kch t tn s 400 Hz v 3000 v/p. V li th ca my pht in khng ng b th hin r tn s cao trn hnh 2 c tnh 6,

nn tc thp v h s cos nh th vic s dng my pht in khng ng b l khng kinh t.

Ti tn s 50 Hz v tc ca 3000 v/p tng khi lng ca my pht in khng ng b v thit b t kch t nh hn khi lng my pht in ng b.

Ti tn s 400 Hz v tc ca 3000 v/p trng lng ca my pht in khng ng b l gim ng k, khi tc cao hn (60008000 v/p), th my pht in khng ng b vi t in kch t c trng lng nh hn 1,5 2,1 ln so vi my pht in ng b v nh hn 35 ln so vi my in cm ng.

Theo [3] khi xt ti yu t hiu sut: trn hnh 3 biu din mi quan h gia hiu sut v cng sut, cho thy hiu sut my pht khng ng b cao hn my pht ng b khi cng cng sut.

tin cy ca my pht in khng ng b tng i cao, c bit vng tc ln, cc my ny khng yu cu bo v ngn mch, v bn thn trong ch t kch n phi ngn mch huy ng ti a cng sut cn thit.

Ngoi ra theo [2] kt qu nghin cu cho thy my pht in khng ng b c th thc hin hot ng cng tc song song tng i d dng, ngay c khi c s khc bit ng k v tn s. Trong trng hp ny tn s ca li in chnh l tn s trung bnh ca cc my pht in ang cng tc song song.

b) M/P, kg/kw

P, kw P, kw

a) M/P, kg/kw

Hnh 3. Mi quan h gia hiu sut v cng sut.

%

P, kw

AG

SG



42

3. My pht khng ng b t kch My pht in khng ng b s dng cng sut phn khng ca mng to ra t thng

do khi cng tc song song vi mng xoay chiu n s nhn t mng lng cng sut ny [1]. Ngoi ra, my pht in khng ng b cng c th hot ng ch c lp vi kh nng t kch nh h thng t in b lp t km theo cng vi my pht [5].

S hnh 4 cho thy my pht in khng ng b (AG), lm vic song song vi li, n nhn dng ti phn khng ML II . V pht ra dng tc dng aI , cung cp cho ti thun tr R.

Khi a cc t in vo hot ng, n ng vai tr l ti dung khng th nhn t mng dng

CI , B t in c tnh ton gi tr CI bng dng phn khng LI . T th vc t ta c dng in khng tiu th ca mng hin ti l :

0 LC II (1.2) Do cu dao P c th ct khi mng, my pht in khng ng b AG s chy c lp

trn mt mng cc b, ch vi ti R v C. Trong trng hp ny, mt mt, my pht in vn tip tc tiu th dng ti phn khng ML II , mt khc, t in tip tc tiu th dng CI bng dng phn khng LI . Nh vy t in ng vai tr nh ngun b cng sut phn khng.

Vy my pht khng ng b cp cho mng cng sut tc dng th gi tr cng sut ca b t in cn bng vi lng cm khng m my pht nhn vo. Nu khng tho mn iu , ti s phi l ti hn hp. Trong trng hp ti l RC th lng t cn thit s nh hn, v mt s iu kin th vic c nhng t ny l khng cn thit.

Theo s tng ng hnh 5 v th vc t my pht khng ng b c m t trn trn hnh 6 ta c th xc nh c cc thng s v cc gi tr tng ng, c tnh lm vic ca my pht. Cng sut phn khng tiu tn trn Mxxx ,,

'21 cng c th xc nh c.

Hnh 5. S tng ng my pht d b. Hnh 6. th vc t my pht d b.

Hnh 4. a, s n gin my pht khi ni vi ti v t in. b, th vc t.

b)

AG



43

Thy rng trn c tnh lm vic ch khng ti n nh ca my pht khng ng b t kch bng t in hnh 7, qu trnh t kch ca my c lai bi ng c s cp v trong cun stator c t d nn xut hin sc in ng duE , sc in ng ny t ln b t vi dng

'CI

chy qua stator ca my pht lm tng cng t thng ca my pht, v sc in ng c tng ln 1E ng thi dng qua t cng tng ln

''CI qu trnh c tip din nh vy. ng c tnh

CC IxU . m t s quan h gia in p v dng dung khng. Qu trnh t kch trn hnh m t iu kin t kch ng bc thang tuyn tnh. ng cong c tnh khng ti CM Ixx )( 1 .

T sc in ng d ta xc nh c dng qua t:

duC

duC CEx

EI 1

' (1.3)

Qu trnh t kch tip tc khi vn tha mn iu kin:

CCCM IxIxx .)( 1 (1.4) V kt thc khi

CCCM IxIxx .)( 1 (1.5) M t qu trnh t kch ca my pht th hin trn hnh 7 vi im kt thc l A. Thy rng

qu trnh t kch ca my pht khng ng b tng t nh i vi my pht in mt chiu. Trong l gi nh rng dng stato ban u vi qu trnh t kch thch xy ra l kt qu

ca dng chy ca t d l dng ban u cng np cho t in tch in. Cng sut ca b t in my pht khng ng b t kch l kh ln (ln n 70-100% cng

sut nh mc ca my pht in) lm cho vic lp t tn km. V vn ny lm hn ch phm vi s dng cc my pht in d b.

4. Kt lun Nghin cu v my in khng ng b ch my pht thy rng: - u im so vi my pht ng b v trng lng, kch thc, tin cy; - Vic p dng my pht khng ng b c cng sut va v nh c nhng li th r rt c

bit vng tn s cao; - Vi cng ngh sn xut siu t cng ngy cng pht trin th vic ng dng rt kh thi, b

t in cn m bo c, trng lng v kch thc ph hp. Ngoi ra, vi my pht khng ng b r to dy qun (My pht d b ngun kp) kt hp vi b iu khin cng sut t hai pha th trong cc lnh vc nng lng ti to loi ng c ny chim u th tuyt i.

TI LIU THAM KHO

[1] Juha Pyrhnen, Tapani Jokinen. Design of rotating electrical machines. Valria Hrabovcov, 2008.

Hnh 7. Qu trnh t kch ca my pht.



44

[2] Andrianov V. N. Elektricheskie mashiny i apparaty. M., Kolos, 1971. [3] Dao Minh Quan. Sovershestvovanie rezhimov raboty sudovogo Asinkhronnogo diezel -

generatora. Odesa, 2011. [4] Radin V.I., Brusnikin D.E., Zokhorovich A.Ye. - Elektricheskie mashiny. Asinkhronnye mashiny.

M., Kolos. 1988. [5] Voldek A.I. - Elektricheskie mashiny. L., Energiya, 1978.

Ngi phn bin: ThS. Vn A

NGHIN CU O HIU SUT BM DNG PHNG PHP

NHIT NG LC HC A STUDY ON THE PUMP EFICIENCY MEASUREMENT USING THE

THERMODYNAMIC METHOD

NCS. VNG C PHC, GS-TS. BAE CHERL O Khoa My in tu bin

Trng i hc Hng hi quc gia Mokpo, Hn Quc Tm tt

Bm c s dng rng ri trong cc nh my cng nghip, trung tm thng mi, tu bin Chng tiu th khong 20% tng nng lng in quc gia. Tn tht l rt ln nu chng cng tc vi hiu sut thp. Do cn phi o hiu sut ca chng v tin hnh thay th hoc bo dng nu hiu sut ca n thp so vi hng sn xut bm a ra. Hiu sut ca bm thng c o theo phng php truyn thng v phng php nhit ng lc hc. Bi bo ny s phn tch phng php nhit ng lc hc gm: nguyn l, cch ch to thit b o, kt qu o c trong thc tin v phn tch u nhc im v kh nng ng dng ca n.

Abstract Pumps are used widely in industrial plants, commercial fields and ships, etc. They consume nearly 20% of the each nation's total electrical energy. Their losses of energy are huge when they have been operated at low efficiency. Thus, pump efficiency can be measured to estimate energy losses. If it is low, the pump will be repaired or replaced with new one. Pump efficiency is usually measured according to traditional technique and the thermodynamic method. This paper will analyze the thermodynamic method: principle, how to make pump efficiency instrumentation (PEI), experimental results and show advantages, disadvantages and application of this method.

Key words: Pump efficiency, Thermodynamic method, Pump formula, Best efficiency point (BEP).

1. Gii thiu Vi phng php truyn thng, hiu sut bm c o theo cng thc sau:

%100P2298)P(PQMM

SD

P (1)

Trong cc thng s ti (1) th vic o lu lng l kh nht. Nhiu h thng bm trong thc t khng lp t ring thit b ny v gi thnh n rt t . Ngoi ra vic lp t n cng rt kh v ph thuc vo kch thc ng ng v vic bo dng, hiu chnh u rt kh thc hin. Phng php nhit ng lc hc vi rt nhiu u im s gii quyt vn ny.

2. Ni dung phng php Phng php nhit ng lc hc [1], [2] c c t nguyn tc bo tn nng lng khi cc

cht lng c truyn i. Phng php ny c pht trin trong nhng nm 1960 ti i hc Glasgow v i hc Strathclyde Scotland, v phng th nghim k thut quc gia Php (Electricite de France) v Austin Whillier (Phng Mines, Johannesburg, Nam Phi). Hiu sut ca bm theo phng php ny c tnh theo cng thc:

may dien robot long

Documents