chieu chay qua nam cham di^n.
^hdn tick vd huang ddn gidi
Nguoi ta CO the tao ra tu truong quay bang each cho dong di?n xoay ehieu
ba pha chay qua ba cupn day cua stato ciia dpng co khong dong bp ba pha. Chpn dap an C .
Cty TNHH MIX nyviiKhang Vift
Chnyto Ah 9
B A I T O A N H O P £ > E N
P H l / Q N G P H A P
De giai mot bai toan ve hop kin ta thuong su dung hai phuong phap sau: 1. Phuong phap dai so
Bi: Can cu "dau vao" ciia bai toan de dat ra cac gia thie't co the xay ra.
B2: Can cii "dau ra" ciia bai toan de loai bo cac gia thie't khong phii hop.
Br. Gia thie't dupe chpn la gia thie't phu hop voi tat ca cac dii kien dau
vao va dau ra ciia bai toan.
2. Phuong phap sii dung gian do vec to trugt.
Bi: Ve gian do vec to (trupt) cho phan da bie't eiia doan mach.
B2: Can cii vao di> kien bai toan de ve phan con lai ciia gian do.
Bx. Dua vao gian do vec to de tinh cac dai lupng ehua bie't, tu do lam
sang to hop kin.
Cdch ve gian do vec ta truat
Buoc 1: Chpn true nam ngang la true dong dien, diem dau mach lam goc (do la diem A).
Buoc 2: Bieu dien Ian lupt hieu dien the qua moi phan bang cac vec to
A M ; M N ; NB noi duoi nhau theo nguyen tac; R - di ngang; L - di len; nguyen tac; R - di ngang; L - di len; C - di xuong.
Buoc 3: Noi A voi B thi vec to A B chinh la bieu dien UAB
Nhan xet:
+ Cac dien ap tren cac phan tu dupe bieu dien boi cac vec to ma dp Ion ty le voi di^n ap hieu dung cua no.
+ Dp lech pha giua cac hieu dien the la goc hop boi giiia cac vec to tuang ling bieu dien chiing.
+ Dp lech pha giira hieu dien the'va cuong dp dong dien la goc hpp boi vec to bieu dien no voi true i.
+ Giai bai toan la xac dinh cac canh, goc ciia tam giae dua vao cac dinh ly ham so'sin, cosin va cac cong thiic khae:
a _ b _ C SinA SinB SinC SinA SinB SinC
A • • / /—^ Uc ^/ B /^^-^ * > UR M
Bi guy el on luy?n thi diii hgc dat diem tot da Vat li, tap 1-he Van Vinh
Trong toan hpc m p t tarn giac se giai dugc neu
biet truoc ba (hai canh 1 goc, hai goc mpt canh, ba canh) trong sau ye'u to'(3 goc va 3 canh).
a2 = b2 + c2 - 2bccos A ; b2 = a2 + c2 - 2accos B; c2 = a2 + b2 - 2abcos C
0 3 v i D U M A U :
V l dM 1: Cho doan mach n h u hinh ve, biet u =100>/2cos(1007tt)V, C
10 -4 - F . H Q P k i n X chi chiia mgt phan t u (R hoac cupn day thuan cam),
71
dong dien trong mach som pha n/3 so v o i d i ^ n ap giua hai dau doan
mach A B . H p p X chiia gi ? di$n tro hoac cam khang c6 gia t r i bao nhieu?
A . ChiiaR; R = WO/Sn
B . Chiia L ; Z L = 1 0 0 / V 3 Q C. C h u a R ; R = 10oV3Q C. C h u a R ; R = 10oV3Q D. C h u a L ; Z L = 10oV3n
AH' X B
'PhAn tich vd hit&ng d&n gidi
Ttr gia thiet de cho ta c6 gian do vecto ^ trupt n h u hinh ve: de i nhanh pha hon u
i.:pt goc — thi u phai nam phia duoi i , ket
3
hpp v o i gia thiet hpp X chi chua mpt phan t i i nen hop X chinh la d i f n tro thuan R. T u hinh ve ta c6: tan 100 3 U R R _ a ^ —• \ i 1 ' Chpn dap an A
V l du 2:6 (hinh ve) hop X chua mpt trong ba phan t u : d i ^ n tro thuan, cuon day, tu di^n. K h i dat vao hai dau AB mpt di^n ap xoay chieu c6 gia t r i Weu day, tu di^n. K h i dat vao hai dau AB mpt di^n ap xoay chieu c6 gia t r i Weu dung 2 2 0 V , nguoi ta do dupe UAM = 1 2 0 V va UMB = 2 6 0 V . H o p X chua: A. cupn day thuan cam. ^ I ^ ^
B. cupn day khong thuan cam. A C M C. d i ^ n tro thuan.
D. tu dien.
B