BI 1: QUN DY MY BIN PA. MC TIUHc xong bi hc ny sinh vin c kh nng:

Tnh ton qun mi my bin p. m bo hot ng tt, t cc thng s k thut theo tiu chun k thut in

Sa cha c nhng h hng ca my bin p mt pha

B. PHNG TIN THIT B (cho 1 hc sinh/ nhm)STTChng loi qui cch k thutS lngGhi ch

1Li thp my bin p EI1 b

2My qun dy1 chic

3Thc pan me1 chic

4Thc l, thc cp, dao gt dy, ko1 b

5M hn thic HAKKO 9361 chic

6Dy emayng knh theo mu li thp

7Khun nha1 b

8Giy cch in, ng ghen, ch hn, S lng cho mi my bin p

C. NI DUNG THC HNHI. TNH TON S LIU DY QUN MY BIN P 1 PHA2. Tnh ton qun li my bin p

L dng bi ton m ngi th c trc mt li thp no . T li thp c sn ny kt hp vi cc yu cu cn c khc (thng thng l in p U2 v U1) s tin hnh xc nh cc thng s cn li sao cho ph hp vi li thp c.a. Tnh ton my bin p cm ng

C th tm tt bi ton nh sau:

Bit trc: Tit din li thp At; U2; U1.

Cn tm: SBA ( I2 ( I1; n1; n2; d1; d2 ...

Cc bc tin hnh nh sau:

Bc 1: T tit din li thp c tin hnh xc nh dung lng SBA theo biu thc:

(1.47) (1.2)

Trong :

At: l tit din tnh ton ca li thp [cm2]

S2: l cng sut biu kin cung cp ti pha th cp bin p [ VA ]

K: l h s hnh dng li thp.

Khi l thp dng EI (hnh 1.2) ta c K = 1 ( 1,2

Khi l thp dng UI (hnh 1.3) ta c K = 0.75 ( 0,85

Bm: l mt t thng s dng trong li thp. Ty theo hm lng silic nhiu hay t m chn Bm cao hay thp. Cng ty theo loi l thp c ch to theo dng dn t c nh hng hoc khng nh hng m chn Bm cao hay thp.

i vi l thp dn t khng nh hng: Bm = (0,8 ( 1,2)T

i vi l thp c dn t nh hng: Bm = (1,2 ( 1,6)T.

Bc 2: Xc nh dng in th cp I2:

(1.48)

Bc 3: V li s hon chnh MBA:

Bc 4: Tnh s vng dy qun cho mi vn (1.49)

Trong :

Tit din li thp c tnh bng m2

Nu tit din li thp c tnh bng cm2 v f = 50Hz th biu thc trn tr thnh.

(1.50)

Bc 5: Tnh s vng qun cho cun s cp v th cp:

*). S vng qun cho cun s cp:

(1.51)

*). S vng qun cho cun th cp:

Khi my bin p mang ti th in p trn ti s st gim mt lng so vi lc khng ti. m bo in p cung cp cho khi my vn hnh th phi tr hao lng st p ny khi tnh ton t (5 ( 15)%.

(1.52)

Bc 6: Tnh dng in pha s cp:

Tra bng chn hiu sut ca MBA v tnh ra dng in pha s cp

(1.53)

S2 ( VA )31025501001000

( (% )6070808590> 90

Bc 7: Tnh ng knh dy qun:

Chn mt dng in thch hp v tnh ng knh dy qun

Pha s cp:

(1.54)

Pha th cp:

(1.55)

Vi J l mt dng in (A / mm2); Chn ty vo ch lm vic ca MBA.

MBA lm vic lin tc J = (2,5 ( 5) A/mm2.

MBA lm vic t J c th chn n 7A/mm2.

Bc 8: Tnh h s lp y (kl)

H s lp y cho bit b dy cun dy chim ch bao nhiu trong ca s ca li thp

(1.56)

Trong :

BD: B dy cun dy

C: B rng ca s c =

Tnh b dy cun dy

Cun s cp c b dy BD1 c tnh t s vng qun n1.

Cun th cp c b dy BD2 c tnh t s vng qun n2.

B dy c cun dy BD = BD1 + BD2 + (1 ( 2)mm.

S vng dy qun cho 1 lp:

(1.57)

Trong :

hK: Chiu di h ca khun qun

d/ : ng knh dy k c cch in S lp dy qun:

(1.58)

Trong :

n: S vng dy ca tng cun (s hoc th cp)

nVL: S vng dy qun cho 1 lp

B dy cun dy s hoc th BD1(2) = nL1(2) . d/i

Tnh khi lng dy qun (W)

(1.59)

Vi: W1; W2 l khi lng ca cun s cp v th cp.

Khi lng ca tng cun dy c tnh theo biu thc.

(1.60)

Trong :

LTB: L chiu di trung bnh ca mt vng dy (tnh bng dm).

n: S vng qun ca cun s cp hoc th cp.

d: ng knh dy qun cun s cp hoc th cp (tnh bng mm2).

W: L khi lng (tnh bng Kg).

* V d p dng:

V d 1:

Cho mt li thp EI c kch thc nh sau:b=49mm, a=28mm, c=14mm, h=42mm. Hy tnh ton qun li my bin p sao cho in p th cp l 110V.

Gii:

Ta xc nh thit din thc ca li thp nh sau:

Bc 1: T tit din li thp c tin hnh xc nh dung lng SBA theo biu thc:

(1.47)

Bc 2: Xc nh dng in th cp I2:

(1.48)

Bc 3: Tnh s vng dy qun cho mi vn

(1.50)

Bc 5: Tnh s vng qun cho cun s cp v th cp:

*). S vng qun cho cun s cp:

(1.51)

*). S vng qun cho cun th cp:

Khi my bin p mang ti th in p trn ti s st gim mt lng so vi lc khng ti. m bo in p cung cp cho khi my vn hnh th phi tr hao lng st p ny khi tnh ton t (5 ( 15)%.

(1.52)

Bc 6: Tnh dng in pha s cp:

Tra bng chn hiu sut ca MBA v tnh ra dng in pha s cp

(1.53)

S2 ( VA )31025501001000

( (% )6070808590> 90

Bc 7: Tnh ng knh dy qun:

Chn mt dng in J=5A/mm2 Pha s cp:

Pha th cp:

Bc 8: Tnh h s lp y (kl) S vng dy qun cho 1 lp:S cp: d1=0,38 mm:

Th cp: d2=0,48 mm:

S lp dy qun:

S cp

(lp)

Th cp

(lp) B dy cun dy s cp BD1= nL1. d/1 =6.0,38=2,3 mmB dy cun dy th cp BD2= nL2. d/2 =5.0,48=2,4 mm

B dy c cun dy BD= BD1+BD2+ 2=2,3+2,4+2=6,7H s lp y Kl=6,7/14=0,5Tnh khi lng dy qun (W)

Vi: W1; W2 l khi lng ca cun s cp v th cp.

V d 2:

Cho mt li thp EI c kch thc nh sau:

b=34mm, a=28mm, c=14mm, h=42mm. Hy tnh ton qun li my bin p sao cho in p th cp l 24V.

Gii:

Ta xc nh thit din thc ca li thp nh sau:

Bc 1: T tit din li thp c tin hnh xc nh dung lng SBA theo biu thc:

(1.47)

Bc 2: Xc nh dng in th cp I2:

(1.48)

Bc 3: Tnh s vng dy qun cho mi vn

(1.50)

Bc 5: Tnh s vng qun cho cun s cp v th cp:

*). S vng qun cho cun s cp:

(1.51)

*). S vng qun cho cun th cp:

Khi my bin p mang ti th in p trn ti s st gim mt lng so vi lc khng ti. m bo in p cung cp cho khi my vn hnh th phi tr hao lng st p ny khi tnh ton t (5 ( 15)%.

(1.52)

Bc 6: Tnh dng in pha s cp:

Tra bng chn hiu sut ca MBA v tnh ra dng in pha s cp

(1.53)

S2 ( VA )31025501001000

( (% )6070808590> 90

Bc 7: Tnh ng knh dy qun:

Chn mt dng in J=5A/mm2

Pha s cp:

Pha th cp:

Bc 8: Tnh h s lp y (kl) S vng dy qun cho 1 lp:S cp: d1=0,3 mm:

Th cp: d2=0,75 mm:

S lp dy qun:

S cp

(lp)

Th cp

(lp) B dy cun dy s cp BD1= nL1. d/1 =7.0,3=2,4 mm

B dy cun dy th cp BD2= nL2. d/2 =2.0,75=1,5 mm

B dy c cun dy BD= BD1+BD2+ 2=2,4+1,5+2=5,9H s lp y Kl=5,9/14=0,42Tnh khi lng dy qun (W)

Vi: W1; W2 l khi lng ca cun s cp v th cp.

b. Phng php tnh ton my bin p t ngu:

i vi my bin p t ngu cn lu cc im sau:

+ Cng dng in trong on cun dy chu ti chung cho c 2 dng in I1 v I2 th ch chu dng in bng hiu ca 2 dng in

I=I1-I2

+ Cng sut biu kin cn thit c xc nh nh sau:

Khi tin hnh tnh s liu dy qun ca my bin p t ngu ta cng tin hnh cc bc nh trn ch tr lu cc im trn.

Th d: Tnh s liu dy qun ca my bin p gia dng theo yu cu k thut sau:U1= 80V, 120V, 160V, 220V; U2= 50- 75V; I2= 5A- 2A; f=50Hziu kin tng gim 11 bc 5V/bc.Kch thc mch t nh hnh v sau (mch t c trong xng). B dy l thp 0,5mm; Bm=0,9 wb/m2 v mt dng in j=5A/mm2

Gii1. Tit din thc ca li mch t, chn k=0,9 At = 0,9(2,8.4,8)=12,1 (cm2)Kim tra mch t c p ng c cng sut d tinh.Ta c cng sut biu kin:

M cng sut cho php ca mch t

101,67VA.So snh S