GEK-86038
the main induction disk unit, a s shown in Figure 9. The rel ay operates to c l o se the
normal l y-open output c ontact s wheneve r the detected temperature exceeds the set'
val ue . These output c ontacts c a n be reset:
a . ma nua l l y
b . el ectric a l l y
c . sel f-reset by mea n s of exte rna l connections
but on l y afte r the detected tempe rature has fal l en bel ow the reset tempe rature of
the main unit and it s right-hand (IRTR) contac t has c l osed . The reset l evel o f the
main unit is continuousl y a djustabl e from soc to 300C bel ow its operating
tempe rature l evel .
The IRT51G rel ay is mounted in a doub l e end, sma l l size d rawout
case .
The type IRT51H is simil a r to the IRT 5 1G except a n RTD probe a s sembl y is
furnished a s a pa rt of the rel ay model . The probe is a th ree wire, sin g l e el ement,
tip sensitive, 100 ohm at ooc, pl atinum RTD .
The probe c omes with a f l uid seal
instal l ation fittin g a nd al so a b ra s s reducing fittin g for use where required (see
INSTALLATIO N PROCEDURE).
APPL I CATION
The type IRT5 1 rel ays can be used to protect any a ppa ratus equipped with one of
the re sista nce temperature detectl1rs l isted in the INTRODUCTION section .
The types
IRT51E and IRT51F rel ays a re intended prima ril y for the protection of motors or
gene rato rs havin g the RTo•s embedded in the windin gs . The usabl e tempe rature ra nge
of sooc to 1650C make s them pa rticul arl y suitabl e for a pp l ication on m achine s with
c l a s s A , B or F insul ation .
These rel ays may a l so be a ppl ied to protect powe r
t ransformers again st overheatin g with a s sociated RTO•s pl aced i n stra te gic l ocation s
in the ta nk .
Typic al external con nection s for the type IRT51E rel ay a re shown in Figure 10 .
Typical external con nection s for the type IRT51F rel ay a re shown in Figure 11.
The types IRT51G a nd IRT51H rel ays a re
tempe rature protection of rotating equipment .
these rel ays are shown in Figure
12.
intended prima ril y for bea ring
Typical external c o nnections for
The functions that temperature re l ays pe r fo rm depe nd upon the type of equipment
to be protected, its importance to the system, a n d its l ocation in the system . In
unattended stations, for exampl e, the IRT51E o r IRT51F rel ays o pe ratin g from
embedded RTo•s may be used to reduce or remove l oa d automatical l y . The type IRT51F
with it s normal l y- ope n (IRTL) a nd normal l y-c l osed (IRTR) contact s coul d a l so be
empl oyed to prevent an inc rea se in l oa d until the tempe rature ha s returned to an
acceptabl e l evel .
In attended station s, the function of these rel ays is genera l l y to provide a
wa rning al arm that an overtem pe rature condition exists, es pecia l l y in the c a se of
majo r unit s and essentia l auxil iary power equipment.
In addition to sounding an
a l a rm, the rel ays may a l s o initiate a timing device which c auses a del ayed automatic
corrective action if the station o perato r has not re s ponded to the a l a rm within a
V
rea sonabl e time .
These rel ays shoul d not be used to determine machine l oad, since operating
temperature is not necessa ril y a rel iabl e indication of maximum permissible l oad .
Other design l imitation s may pl ace more st
4
ingent restrictions on mac hine ratin g .
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