GE AKR-30 Series Maintenance Manual page 243

FIG. 88 TEST SET, CAT. NO. TVTS 1
1 2.4.1 R ESISTANCE VALUES
For use i n troubleshooting the M i croVersaTrip'M
current sensors, the resistance of the tapped and fixed
windings is g iven in Tables 13 and 1 4 respectively.
TABLE 1 3 - TAPP E D SENSO R R ESISTAN CE
VALUES
Ampere
Tap
1 00
1 50
225
300
300
400
600
800
600
800
1 200
1 600
800
1 200
1 600
2000
TAB LE 1 4 - FIXED SENSO R R ESISTANCE
VAL U ES
Ampere
Rating
1 00
1 50
225
300
400
600
800
1 200
1 600
2000
The coil resistance of the M icroVersaTrip flux shifter
device i s approxi m ately 7 ohms.
Resistance in Ohms
Between Common
and Tap Terminals
7.0-8.2
1 0- 1 2
1 5- 1 8
20-24
20-24
27-32
42-50
58-68
42-50
53-68
93- 1 09
1 30- 1 54
74-88
1 1 6- 1 36
1 62-1 90
2 1 0-246
Resistance in Ohms
Between Terminals
6.7-7.8
1 0- 1 2
1 5- 1 7
20-24
27-32
42-50
58-68
92- 1 08
1 29- 1 5 1
207-243
SECTION 1 2- Micro Versa Trip
Trip Device (Cont.)
1 2.4.2 FALSE TRI PPI NG-B R EAKERS
EQU I PP E D WITH G R O U N D FAU LT
When nu isance tripping occu rs on breakers equipped
with the G round Fault trip element, a p robable cause is
the existence of a false "g round" signal. As ind icated by
the cabling d iagram of Fig. 90, each phase sensor is
connected to su m m i ng ci rcu itry in the p rogrammer. Un­
der no-fault cond itions on 3-wi re load ci rcu its, the
cu rrents i n this circu itry add to zero and no ground
signal is developed . This cu rrent sum will be zero only if
all th ree sensors have the same electrical charac­
teristics. If one sensor d iffers from the others (i .e. , d if ­
ferent rating or wrong tap setting), the circuitry can
p rod uce output sufficient to trip the breaker. S i m i larly,
d iscontinu ity between any sensor and the p rogrammer
unit can cause a false trip signal.
If n u isance tripping is enco u ntered on any b reaker
whose M icroVersaTrip components have p reviously
demonstrated satisfactory performance via the TVTS1
Test Set, the sensors and their connections should be
closely scrutin ized . After d isco nnecti ng the b reaker from
all power sou rces.
a) Check that all phase sensors are th e same type (am­
pere range) .
b) E nsure that the tap settings on all 3-phase sensors
are identi cal .
c) Verify that the harness connections to the sensors
meet the polarity constrai nts i ndicated by the cabl i ng
diagram.
d) On G rou nd Fault breakers serv i ng 4-wire loads,
check that the neutral sensor is properly con nected (see
cabling di agram Fig. 91 ) . In particu lar,
( 1 ) Verify that the neutral sensor has the same rating
and tap setti ng as the phase s ensors.
(2) Check conti nuity between the neutral sensor and its
equi pment-mou nted secondary discon nect block. Also
check for conti nuity from the breaker-mou nted neutral
secondary disconnect block through to the female harness
connector.
(3) If The b reaker's lower studs con nect to the supply
sou rce, then the neutral sensor must have its LOAD end
con nected to the sou rce. See Fig. 92.
(4) Ensure that th e neutral conductor is carrying only
that neutral current associated with th e breaker's load cur­
rent (neu tral not shared with other loads) .
e) If the preceding steps fail to identify the problem, then
the sensor resistances should be measu red . Si nce the
phase and neutral sensors are electrically identical , th eir
tap-to-tap resistances should closely agree. See Tables 1 3
and 1 4 .
T M
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