FIG. 88 TEST SET, CAT. NO. TVTS1
1 2.4.1 RESISTANCE VALUES
For use i n troubleshooting the M icroVersaTriprM
current sensors, the resistance of the tapped and fixed
windings is g iven in Tables 1 3 and 1 4 respectively.
TABLE 1 3 - TAPPED SENSO R RESISTANCE
VALUES
Resistance in Ohms
Ampere
Between Common
Tap
and Tap Terminals
1 00
7.0-8.2
1 50
1 0-1 2
225
1 5-18
300
20-24
300
20-24
400
27-32
600
42-50
800
58-68
600
42-50
800
53-68
1 200
93-109
1 600
1 30-1 54
800
74-88
1 200
1 1 6- 1 36
1 600
1 62-1 90
2000
21 0-246
TABLE 1 4 - FIXED SENSOR RESISTANCE
VALUES
Ampere
Resistance in Ohms
Rating
Between Terminals
1 00
6.7-7.8
1 50
1 0- 1 2
225
1 5- 1 7
300
20-24
400
27-32
600
42-50
800
58-68
1 200
92-108
1 600
1 29-1 5 1
2000
207-243
The coil resistance of the MicroVersaTrip flux shifter
device is approximately
7
ohms.
SECTION 1 2-MicroVersaTrip ™
Trip Device (Cont.)
1 2.4.2 FALSE TRIPPING-BREAKERS
EQUIPPED WITH G ROU ND FAU LT
When nuisance tri pping occu rs on breakers eq u i p ped
with the G round Fault tri p element, a probable cause is
the existence of a false "ground" signal. As ind icated by
the cabling d iagram of Fig. 90, each phase sensor is
connected to su m m ing circuitry i n the program mer. Un
der no-fault cond itions on 3-wire load circuits, the
currents in this circuitry add to zero and no g round
signal is developed . This cu rrent sum will be zero only if
all three sensors have the same electrical charac
teristics. If one sensor differs from the others (i.e., d if
ferent rating or wrong tap setting), the circuitry can
produce output sufficient to trip the breaker. Similarly,
d iscontinu ity between any sensor and the programmer
unit can cause a false trip signal.
If nu isance tri p ping is encou ntered on any breaker
whose M icroVersaTrip com ponents have previously
demonstrated satisfactory performance via the TVTS1
Test Set, the sensors and their con nections should be
closely scrutin ized . After d isconnecting the breaker from
all power sou rces.
a) Check that all phase sensors are the same type (am
pere range) .
b) Ensure that the tap settings on all 3-phase sensors
are identical.
c) Verify that the harness connections to the sensors
meet the polarity constraints i ndicated by the cabli ng
diagram.
d) On G rou nd Fau lt breakers serving 4-wire loads ,
check that the neutral sensor is properly connected (see
cabling diagram Fig. 91 ) . In particular,
( 1) Verify that the neutral sensor has the same rati ng
and tap setting as the p hase sensors.
(2) Ch eck conti nuity between the neutral sensor and its
equipment-mou nted secondary disconnect block. Also
check for conti nuity from the breaker-mou nted neutral
secondary disconnect block through to the female harness
connector.
(3) If The breaker's lower studs con nect to the su pply
sou rce, then tre :-�eutral sensor must have its LOAD end
con nected to the source. See Fig . 92.
(4) Ensure that the neutral conductor is carrying only
that neutral current associated with the breaker's load cur
rent (neutral not shared with other loads) .
e) If the preceding steps fail to identify the problem, then
the sensor resistances should be measured . Since the
phase and neutral sensors are electrically identical , thei r
tap-to-tap resistances should closely agree. See Tables 1 3
and 1 4 .
65
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