Hitachi H20-T Technical Notes page 51

(14) Aft er a n a cciden t cu rr ent flows, do n ot u se t he switch with ou t check in g.
In vest iga t e t h e ca u se of a cciden t t o r em edy it , a n d a lso con fir m t h a t t h e equ ipm en t is fr ee fr om da m a ge ; t h en ,
u se t h e swit ch a gain . Wh en a sh or t circu it cu rr en t flows, it is n ecessa r y t o pa y at ten t ion to t he m eltin g of con t a ct
of t h e cont a ct or, wir e-br ea kin g of t h e h eat er a nd ch a n ge of t rippin g ch a r act er ist ic of t h er m al over load r ela y.
(15) Wh en con n ect in g a power con den ser, do n ot con n ect it t o t h e prim ar y side of t h e st ar t er .
Th e power con den ser is con n ect ed t o t h e secon da r y side of t h e st a r t er or t h e t er m in a ls of t h e m ot or . Wh er e t h e
power conden ser is con n ect ed t o t h e pr im a r y side of th e st a r t er a n d t h e cir cu it is ph a se fa ilu r e du e to on e ph a se
fu s in g, a r ou n d a bou t cir cu it is m a de u p pa s sin g t h e p ower con d en ser a n d a volt a ge of a bou t 50 t o 60% of t h e
power sou r ce volt a ge is applied to t h e coil; t h is ca uses flappin g of t h e con t act or .
F ig. 43 Cor r ect insert ion of power condenser
(16) Do n ot rem ove t h e cover of t h er m al over loa d r ela y, or t ou ch its in ter n a l m ech an ism.
As t h e t h er m al over loa d r ela y is str ict ly a djust ed a t t h e fa ct or y, be su r e n ot t o t ouch t h e in ter n a l m echa n ism.
(17) Do n ot set t he cu r ren t of th erm a l overload rela y a t a poin t h igh er t ha n needed.
E ven in ca se of m ot or s wit h t h e sa me ca pacit y (k W), th e loa d cu rr en t va r ies wit h t he n u m ber of poles a n d types,
so t h at it is n ecessa r y to set cor rectly th e a djust in g k n ob t o t h e m otor cu rr en t.
Do n ot r a ise t h e set va lu e t o pr even t occasion a l oper ation . Sin ce t h e occu rr en ce of oper a t ion m ust be du e t o some
ca u se, fir st, in vest iga t e t h e ca u se a n d r em edy it . Ot h er wise, t h er e is a possibilit y t h a t a m a jor tr ou ble m a y t a k e
pla ce.
(18) Th e t herm a l over loa d rela y sh ould n ot be reset when th e power is left on.
It is n ecessa r y t o r eset t h e t h er m a l over loa d r ela y a ft er t u r n in g off t h e power s ou r ce for s a fet y. Reset t in g m u s t
be m a de aft er t h e ca use of t r ip is elim in at ed.
(19) F or t h e wir in g t o t he t h erm a l over load r ela y, a wire wit h a n appropria t e dia met er sh ould be u sed.
If t he wir e is fin e, th e oper a t in g time becom es fast a n d if it is th ick , th e oper a t in g tim e, slow.
(20) Do n ot m ou n t th e sta r ter a n d con t a ct or upside down, or hor izont a lly.
F ir m ly m ou n t t he st ar ter a n d cont a ct or to a void oper at in g fa ilur e or lowered br ea kin g ca pacit y. (see pa ge 36)
(21) If t h e con t a ct or closes in a fla ppin g m a n n er (a st a t e wh er e t h e con t a ct or is n ot per fect ly closed, bu t vibr a t es
gr ea t ly dur in g closin g), do n ot use t he con t act or cont in u ously.
Th is will ca u se m elt in g of con t a ct , r elea se fa ilu r e, a n d ot h er t r ou bles. In vest iga t e t h eir ca u ses a n d elim in a t e t h is
er r oneous closin g.
(22) Do n ot rem ove u n necessa r y cont a ct s.
Th eir r em ova l m a y r esu lt in a loss of ba la n ce of t h e m ech a n ism a n d h a ve a n a dver se effect on t h e per for m a n ce
of t h e cont a ct or. (Be su r e t o fu lly t igh ten t h e t er min a l scr ews.)
F ig. 44 In cor r ect insert ion of power con denser
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