Hitachi H100C, Technical Notes

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3-3 AP P LICATION AND SE LE CTION
Select ion of t h er m a l over loa d r ela ys m u st be det erm in ed by t ak in g in t o con sider a t ion t h e t ype of m ot or , r equ ir ed
fu n ction, t ype of loa d a n d st ar t in g m et h od, et c.
3-3-1 Gen er a l Select ion
Ta ble 21 gives t h e gen er a l select ion in ca se r u n nin g a n d st oppin g do n ot in clude inch in g a nd plu ggin g a n d t h e st ar t in g
t im e is n ot so lon g.
If t h e pr oba bilit y of ph a s e fa ilu r e a n d n ega t ive p h a se t r ou ble is con s id er ed t o be ext r em ely low, select ion of
st a nda rd t ype (1E ) t h er m a l over loa d r ela y m ak es it possible t o pr ot ect t h e m ot or a lm ost complet ely.
Ta ble 21. Gen er a l select ion
Su bm er ged pu m p
a n d m ot or
Qu ick r esponse t ype
1E t h er ma l over loa d r ela y
Qu ick r esponse t ype
2E t h er ma l over loa d r ela y
Motor u p t o
200k W
3 -elem en t
1E t h er m a l over loa d r ela y
Mot or of less t h a n
3.7 k W
2-elem ent
1E t h er m a l over loa d r ela y
G
e
n
e
ra
l-
p
u
r
p
o
s
e
m
o
to
r
Ver y sm all ca pa cit y
m otor
3-lem ent
1E t h er m a l over loa d r ela y
2E t h er ma l over loa d r ela y
St a tic 3E r ela y
－
Rou gh pr ot ection t o
P h a se failu r e
Mor e st rin gen t ph a se-fa ilur e prot ect ion
Object
Requ ir ed
fu n ction
Overloa d/rest r ict ion pr ot ect ion
3-3-2 Select ion for Sm a ll Ca pa cit y Motor
Th e rea son s wh y a 2-elem ent 1E t h erm a l over load r elay is select ed for a sm a ll ca pacit y mot or of less t h a n 3.7kW
in Ta ble 21 ar e a s follows :
･
E ven in t h e ca se of 2-elem en t t h erm a l over loa d r ela y, t h e ph ase-fa ilu r e oper a t in g perform a nce is ext r em ely h igh .
Th e 2-eler nen t t h er m al over load rela y h as t h e sam e ph ase-fa ilu r e oper a tin g per form a n ce (conform t o IE C st a ndar d)
a s t h e 3-elem en t t ype.
･
Th e sm a ll ca pacit y m ot or h as a ch a r act er ist ic t h a t t he win din g t em per a t ur e r ise is lower at ph ase-fa ilu r e r un n in g
com p a r ed wit h m ed iu m - or la r ge ca pa cit y m ot or s d u e t o st r u ct u r a l r ea s on s , s u ch a s st a r -con n ect ion of m ot or
windin g.
F ig. 25 in dica t es t h e exper im ent a l va lu es of t h e t emperat u r e rise r a t io a t pha se-fa ilu re. F ig. 26 indicat es con ver sion
of t h e experim en t a l va lu es in F ig. 25 int o t em per a t ur e r ise r a t io a t oper at ion of t h er m al over load rela y. Wh en u sin g
t h e 2-elem ent t ype wit h h igh perform a nce, it is possible ju dgin g fr om t h e figur e t o m a ke pr ot ect ion at ph ase-failur e.