GEK-49950
POWE R
GENE RAL
All devices operated on alternating cu rrent {AC} a re affected b y freq u en cy. A n o n
si nusoidal w aveform can be analyzed as a fundamental freq uency pl us h a rmon ics of that
fu ndamental freq uency. AC rel ays { and AC devices in general) are
affected b y
the appl i cation of non-si n usoidal w avefo rms. Therefo re, i n
t o test A C rel ays
pro perl y it is essential to use a test voltage and/or cu rrent w aveform that is sin usoidal. The
pu rity of the si ne w ave { i. e., its freedom from harmonics) cannot be ex pressed as a fin ite
n u mber for any particul a r relay; how ever, any rel ay usi ng tuned ci rcu its, RL or RC
netw o rk s, or satu rati ng el ectromagnets {such as time- overcu rrent rel ays) w o ul d b e
essentially affected b y non-sin usoidal waveforms. Hence a resistance-l i mited ci rcu it, as
show n in Fig u res 1 1- 1 3, is recommended.
TI ME- OVE RCU RRENT UN IT
Rotate the time dial slowly and check, by means of a l a m p, that the contacts j ust close at
the zero
(O)
time-dial setting.
The point at w h ich the contacts j ust cl ose can be adj usted b y run n ing the stationary
contact b rush i n or out by means of its adj usti ng screw.
W ith the contacts j ust closi ng at the zero (0) time setting, there should b e sufficient g a p
b etw een the stationary-contact b rush a n d its metal b ack i n g stri p to ensu re a p p rox i matel y
1/ 32- i nch w i pe.
The m i n i m u m cu rrent at w h ich the contacts w ill j ust cl ose is determi ned b y the tap sett i n g
i n the tap bl ock at the top of the su pport structu re. See
CHARACTERISTICS
section.
The pick u p of the ti me- overcu rrent u n it for any cu rrent-tap setting is adj usted b y means of
a spri ng- adj usti ng ring (see Fig ure 1). The spring- adj usti ng ri ng either w inds or u n w i nds
the spi ral control spring. By turning the ring, the operating cu rrent of the u n it may b e
b roug ht i nto ag reement w ith the tap setting employed, i f this adj ustment has b ee n
d istu rb ed. Th is adj ustment also permits a n y desi red setting i ntermed iate b etween the
various tap sett i ngs to b e obtained. If such
is req u ired, it is recom mended that
the hig her tap be used. It should be
noted
the rel ay w ill
not
necessaril y agree w ith
the ti me- cu rrent characteristics of Fig ures 5 and 6 if the rel ay has b een adj usted to pick up
at a val ue other than tap val ue, b ecause the torq ue l evel of the rel ay w ill have changed.
Time
The setting of the ti me dial determines the l ength of time that the u n it req u i res to close
the contacts'w hen the cu rrent reaches a predet ermined val ue. The contacts a re j ust closed
w hen the time dial is set on zero (0). W hen the time dial is set on 1 0, the d isk must travel
the max i mu m amount to close the contacts and therefore this setting gives the max i m u m
time setting.
The primary adj ustment for the time of operation of the u n it is made b y means of the time
d ial. H ow ever, fu rther adj ustment is obtained by moving the permanent magn et
its
su pporti ng shelf; movi ng the magnet toward the disk and shaft d ecreases the time,
movi ng it aw ay i ncreases the time.
Test
Set the rel ay at the 0.5 time- d ial position and the l owest tap. W ith the test con nections as
i n Fig u re 1 1 , the main u n it shoul d cl ose the contacts w ith i n
±
3% of ta p- val ue cu rrent.
1 1
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