C. 4,35Q d 2,175n
b) Vong tutre (mac tutre) cl m9t s6 gia tri giCli h~n khac nhau cua h/c tu
C- ong d9 tu' tr- ong trong khe hd hay trong v$t li$u khong tu se d- 9c tf nh theo cong thuc:
Bo 6
H0 =-~0,8.10 B0
µo
0 day: H0 d- 9c xac d[nh bang Alm),
B0 : bang tesla.
Hay H0= 0,8.B0 neu H0 d- 9c xac dinh bang A/cm va B0 bang gauss. Theo ly thuyet cua Ampe, tong so cua cac tu' ap tren tat ca cac do9n cua m9ch tu' la bang voi dong tong.
H111+ H212+ H010+ .... = lco.
Vf du:
Can bao nhieu vong day quan tren 16i (hlnh 4.8) d- &i day d~ c6 m9t tu' thong
47.104Wb, gia thiet rang dong di$n trong cu9n day la 25A va phan phfa tren cua 16i d- 9c lam bang thep 3 330 va phan phfa d- &i lam bang thep khuon?
0o~m dau tren cua ba do~m bang thep 3 330 c6 chieu dai 540 (0,54m) va tiet dien S1 = 36cm2 (0,0036 m2), do~m thCt hai bang thep khuon c6 12= 17 cm (0, 17m) va S2 = 48cm2 (0,0048m2), do~m th Ct ba d-(Jc ts¼o nen b6i m9t khe hc:5 10= 5 x 2 = 1 0 mm (0,01 m) va S0= 36cm2 (0,0036m2). 0 _ _ _ _1 _ _ --.... -.-+--+---,-.---.---. I I -+t----'----t4-6_0 I 60 I s::t 0 C") co I I L!) N I I r-------<1 150
H1nh 4.8: M9ch tu' cua vf d1,1 H1nh 4.9: 8- cing cong tu' h6a thep (d-ong so 2) 3 330
Bal giau:
Cam Ctng tu' trong cac do9n th Ct nhat, hai va th Ct ba la:
B = <1> = 47.10-4 =l3T 1 SI 36.10-4 ' B2 =-<l> = 47.10-4 = 0 98T S2 48.10-4 ' B = ~ = 47.10-4 = l 3T 0 S0 36.10-4 '
Theo d- dng cong ta h6a ti! nhien doi v&i thep 3 330 (H1nh 4.9) ta thay rang cam Ctng ta 1,3T t- e5ng Ctng v&i c- ong d9 tu' tr- dng 750A/m.
- TU' ap tren do9n thCt nhat la:
Um1= H1l1= 750 X 0,54 = 405 A.
- C- ong d9 tu' tr- dng tren do9n th Ct hai la:
H2= 400A/m - TU' ap tren do~m thu hai la:
Um2= H212= 400 x 0, 17 = 68 A. - C- dng de) W tr- dng trong khe ha la:
H0= 0,8.106.B0 = 0,8.106 x 1,3 =1,04. 106 Alm
- TU' ap trong khe ha la:
Umo= H010= 1,04. 106
X 0,01 = 10400 A.
- Sue W d9ng la:
Fm= Um1 + Um2 + Umo = 405 + 68 + 10400 = 10873 A. - S61- c;,ng vang cua cu9n day la:
OJ= F,n = 10873 =435vang.
I 25
4.3. Ho holilg thoorig gap:
Gae lo9i v$t li$u dan W d- c;,c sll' d1:.1ng d§ che t90 cac m9ch W cua cac thiet b! di$n, may di$n va khf cy di$n, nen khi sll' dyng lau ngay se b! h- hong va ta th- dng g~p cac d9ng h- hong sau: