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B. ROLE TRUNG GIAN
Role trung gian la khf c1,,1 di$n dung de khuech d?i gian tiep cac tfn hi$u tac d(mg trong cac m9-ch dieu khien hay bao v$ ...
Trong m?ch di$n, role trung gian th- crng nam giCl'a hai role khac nhau (v1 dieu nay nen c6 ten la trung gian).
4.1. Ca'u t�o:
Cu9n day hut cua role trung gian th- crng la cu9n day di$n ap va khong c6 kha nang dieu chinh gia tr! di$n ap. Do v�y, yeu cau quan tr9ng cua role trung gian la d9 tin c�y trong tac d9ng. Ph?m vi gia tr! di$n ap lam vi$c cua role trung gian th- crng la U6m .±1 5%. H$ thong tiep diem ph1,,1 thu9c vao tu'ng lo?i ro le va chi c6 tiep diem ph1,,1 khong c6 tiep diem chf nh, cac tiep diem th- crng nho va giong nhau.
4.2. Nguyen ly ho�t d(>ng :
Nguyen ly ho?t d(mg cua role trung gian la dlfa tren nguyen ly di$n tu'. Khi d- a di$n ap xoay chieu thf ch hc;:Jp vao hai dau cu9n day cua role th1 phan cam se hut phan Ctng lam d6ng, mb h$ thong tiep diem. Khi cat dong di$n cua cu9n day role th1 cac tiep diem trb ve
tr?ng thai ban dau.
B9 tiep xuc (h$ thong tiep diem) cua cac role trung gian th- dng c6 so luc;:Jng t- ong doi 16n, th- crng 16n hon rat nhieu so v6i cac role dong di$n, role di$n ap cOng nh- cac lo?i role khac.
Role trung gian ch1 lam vi$c C1 m9-ch dieu khien nen n6 chi c6 tiep diem ph1,,1 ma khong c6 tiep diem chfnh. C- dng d9 dong di$n di qua cac tiep diem la nh- nhau.
4.3. Trnh ch9n rdle trung gian:
Khi tfnh ch9n role trung gian ta can chu y cac diem sau: - 0i$n ap djnh mCJ'c cua rdle: urcJle = um�ng
- Dong di$n djnh mCJ'c: lam rcJle > ltt
(ltt la dong di$n tfnh toan cua m9ch) - So I- gng tiep diem.
- Lo9i tiep diem th- ong d6ng va th-ong md.
- Can cu' vao nhu cau sU' d1,mg ket hgp vdi cac diem tren de ch9n lo9i rdle c6 cac thong so thfch hgp.
❖ Cyc ky hi�u:
Trong qua tr1nh lap rap cac m9ch dieu khien dung role hay trong cac m9ch di$n tlf c6ng nghi$p, ta th- ong g?P m9t so ky hi$u sau day d- gc dung cho Role.
r··--.. � 5 ----4::L._f"-i ♦...,i_4_ ----4::L._f"-i ♦...,i_4_ 1 ' i : ....... J RCJle SPDT + Ky hi�u SPOT: RCJle SPST l +: 3 ' ., ! +1 s 1 ' i . � RCJle DPST DPDT
Ky hi$u nay d- gc viet tat tu' thu?t ngG': SINGLE POLE DOUBLE IHROW, Rdle mang ky hi$u nay th- dng c6 m9t C?P tiep diem th- dng d6ng va m9t C?P tiep diem th- dng mc:1, hai C?P tiep diem nay c6 m9t dau chung vdi nhau.
+ Ky hi�u DPDT:
Ky hi$u nay d- (Jc viet tat tu' thu?t ngG': DOUBLE POLE DOUBLE IHROW, Rdle. Rdle mang ky hi$u nay gom c6 hai C?P tiep diem th- dng dong va hai C?P tiep diem th- dng md. Cac tiep diem nay lien ket thanh hai h$ thong, moi h$ thong bao gom m9t C?P tiep diem th- ong dong va th-ong md c6 m9t dau chung nhau.
+ Ky hi�u SPST:
Ky hi$u nay d- (Jc viet tat tu' thu.)t ngG': SINGLE POLE SINGLE IHROW, Rdle mang ky hi$u nay chi c6 m9t C?P tiep diem th- dng md.
+ Ky hi�u DPST:
Ky hi$u nay d- gc viet tat tu' thu?t ngG': DOUBLE POLE SINGLE IHROW, Rdle mang ky hi$u nay gom c6 hai C?P tiep diem th- cJng md.
Ngoai ra, Rdle lap trong tu dieu khien th- ong d- gc d?t tren cac de chan ra. Tuy theo so I- gng chan ra, ta c6 cac kieu de chan khac nhau: de 8 chan, de 11 chan ...
H1nh 4-8. H1nh d,;mg ngoai va cau t?o ben trong
cua Rdle trung gian do hang OMRON san xuat H1nh 4-9. D?ng de 8 chan
4.4. Hu hong va nhf!ng nguyen nhan gay hu'. hong:
Doi v6i role trung gian ta th-ang thay nh[fng h- hong sau day:
• Huhong tiep diim
+ Nguyen nhan:
- Life ep tren cac tiep diem kh6ng du.
- Gia da tiep diem kh6ng bang ph�ng, cong, veng.
- Be m�t tiep diem b! oxy h6a do xam thlfc cua moi tr- ong lam vi$c ( c6 h6a chat,