Electrical Test
lnstruments MAC-20 Retrofit
Package
Section lll
-
Operating Instructions
4. Setup MAC-20 for
C.L. MOM.
5. Set MAC-20 RANGE
to lowest range
that is
greater
than desired test current.
6. Set
TIMEBASE
to CYCLES.
7. Press PRESET
key. Adjust
preset
time to 2.0 cycles.
8. Press
PRESET again to return
to normal mode.
9. Select MEMORY
mode.
10.
Repeatedly
jog
the
INITIATE
button, while
adjusting the OUTPUT CONTROT
higher,
until the desired test
current is read on the ammeter.
lf insufficient current is
obtained at maximum
position
of the vernier,
set the OUTPUT TAP
control to the
next higher
tap, return the vernier
to zero, and continue.
'l
1. Press RESET
button.
12.
Set TIMEBASE to SECONDS.
13.
Select
LATCH
mode.
14. lf
desired,
N.C.
mode may be used;
connect contacts leads to an
unused
pole
of
the breaker.
15. Press and release INITIATE
key; CLOSE or
OUTPUT ON light should
glow,
timer
should run, and current display
should read desired output current.
16. While test is running, observe
current reading. lf necessary, adjust
to correct value
by using vernier control.
17. When breaker trips,
the test set output should de-energize,
timer should stop,
CLOSE or OUTPUT ON light should
turn off, and TRIP or OUTPUT OFF light
should
glow
(lf
applicable).
18. Read and record
trip current and trip time. Compare
to
manufacturer's
time/current
curve. lf necessary, adjust
the trip unit and repeat the test.
19.
Repeat
the above tests for the other
poles
of the breaker,
allowing time for breaker
to cool. Note: Results are acceptable if
all
poles
of the breaker trip within the
manufacturer's
time
range
for the value of test current chosen. AII
poles
of
the
breaker need not
trip
in
exactly the same amount of time.
20. Shut down
test set, disconnect breaker, and
prepare
for
subsequent testing or
relocation according to steps 20
through
25 in
general
procedures
outlined above.
Timing Test, Short Time Delay
Note: The breaker's trip time for short time delay will always be less
than 30 cycles and
may be
as low
as
4-5
cycles.
Therefore,
setting test current will require some
practice.
However, the magnitude of the test current is not critical; for instance, if the S.T.D. is
set for
1000
amperes, there
will
be
little
or
no difference in
timing
if
a test current of
1500, 2000 or 2500
amperes
is used.
Copyright(C)
1
994-1 998
All
Rights
Reserved
Electrical
Test lnstruments,
lnc.
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