Hitachi H100C, Technical Notes

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Th e st a r t in g t or qu e becom es ext r em ely sm a ll, so t h a t st a r t in g will be im possible u n less t h e load is a con sider a bly
ligh t on e.
Referen ce 2. Effect due t o volt a ge u n bala n ce (Wh ere 2-elem en t t h erm a l over loa d r ela y is used)
E ven in case t h e loa d is ligh t a nd st ar t in g is possible, if a 2-elem ent t her m a l over load r ela y of a low r at in g is u sed,
t h er e r em a ins a pr oblem of volt a ge u n ba la n ce. Th e lower t h e ra t in g (h eat er r esist a nce is lar ge), t he gr eat er t h e volt a ge
u n ba la n ce. Th er efor e, u n des ir a ble m ot or r u n n in g con d it ion s w ill con t in u e, su ch a s cu r r en t u n ba la n ce, a bn or m a l
t emper a t u re r ise, et c.
Wh en usin g a 2-elemen t t herm a l over loa d rela y
(RC 0.1A) to th e m ot or (0.1A r at in g), cu rr ent
u n ba la n ce of a lit t le over 50% m a y occu r.
Referen ce 3. H eat er resista n ce of t h er m a l over load r ela y
Th e t h er m al overloa d r ela y is design ed t o act u at e t h e con t a ct m ech a n ism by dr ivin g t he bim et al u sin g t h e h ea t in g of
t h e in t er n a l h eat er a r isin g fr om over loa d cu rr ent of t h e mot or.
Th e m in im u m power n ecessa r y for t h is h ea t in g sh ou ld be m or e t h a n 1.3W (on e ph a se com pon en t wh en t h e r a t ed
cu r r en t is flowin g).
W (power) = I 2 (r a ted cu r r ent 2 )
×
R (h eat er r esist a n ce valu e) = 1.3 to 8 (W)
･
H ea ter r esist an ce va lue: In t he case of a low r at in g, t h e hea t er r esist a nce va lu es ca n be calcu lat ed fr om a bove power
a s sh own in t he followin g ta ble.
Ta ble 22. H ea ter r esist a nce
Ra t ed cur r ent
(RC)
H eat er r esist an ce va lu e
(on e ph ase)
Con dit ion
0.3A 14.4
Ω
0.2A 32.5
Ω
0.15A 57.8
Ω
0.10A 130
Ω
W (Power)
・・・・・
1.3 W (m in im um va lu e)
Ra t ed cur r ent
・・・・・
A low r at in g less t h an
RC0.3A.
Wh en t h e r at ed cur r ent becom es sm a ll, t h e h eat er resista nce va lue is indicat ed to becom e extr emely la r ge.