ABB CIRCUIT SHIELD 49/50 Petunjuk Manual - Halaman 12
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Halaman Cetak
Motor Overcurrent Relay
IB 7.2.1.7-4
Page
12
To check the STALL (51) function, set the Fault dial at 8 multiples (or higher) to avoid instantaneous
operation.
Set the
Overload dial at 5 to avoid overload operation. Depress and hold the TRIP button. The relay should operate in
approximately the time in seconds set on the Stall dial and a target should be displayed for the 51
function.
(The pickup led
should flash during this test, indicating proper operation of the overload unit.)
The above tests are quick functional checks that can be performed without test equipment. High accuracy should not be
expected.
RETURN ALL SETTINGS TO ORIGINAL
VALUES.
4. ACCEPTANCE TESTS
A typical test circuit for use with a single-phase test current source is shown in Figure 7. The test current connections must
be as shown. Also, since the relay is designed for three-phase applications and responds to the average of the 3 phase
currents, a test current correction must be made for single-phase testing: the test current source must be set to 1.5 times
the desired test currenc to obtain the correct response. (If a three-phase
test
source is
available,
no correction
would
be
required).
Apply proper control power per the nameplate rating of the relay.
Thermal memory considerations: when control power is initially applied to the relay, the thermal memory is set at
approximately half-way to the trip point. Therefore, during testing it is preferable that the control power be applied
continuously.
Also, terminals 15
and
16 should be momentarily shorted prior to
any
timing test of the overload (49)
element, to insure that the thermal memory is fully reset.
Interaction Between
Elements:
some settings and test currents may cause the relay to trip on a function other than that
expected. Check the time-current
curves
for the planned test current level and time-dial settings prior to running a test.
Usually one or more dials can be set temporarily higher to avoid such interaction.
Pickup test: set the desired tap (use 2.5
if
none
specified).
The vernier should be fully counterclockwise. Increase
the
test
current slowly until the pickup lamp begins
flashing.
Note the test current (Remember the l .5x factor when testing
with a
single-phase source). Pickup should be
within
+/-10% of the tap setting (3.37
-
4.13 amperes ifthe 2.5 ampere tap
is
used
with single-phase testing). Pickup may then be set exactly to the desired
value
using the vernier adjustment.
Fault Unit
(50):
set the Stall dial to
maximum.
Set the Fault dial to the desired setting (use 8x it none
specified).
Increase
the current quickly to determine the instantaneous unit pickup
current.
Do not
apply
high currents more than
a
few
seconds due to the thermal
stress.
If
the
unit does not trip immediately remove the
test
current
and
review
your
procedures.
(Remember the l .5x factor when testing with
a
single-phase source). The setting may be trimmed as necessary to obtain
the required operating
value.
(If a setting of less than
6x
is to be used, the final adjustment must be deferred until the stall
function is checked). Timing tests of the Fault element are not recommended due to the difficulties in controlling and
measuring very short
times.
If a timing test must be run, preset the test
current
for 2 times the fault element pickup setting.
Operating time of0.03 seconds or less
is acceptable.
Stall Unit (51): set the Fault dial at 8x or
higher.
Set the Overload dial
at
5. Set
the
Stall dial to the desired delay. (Use 10
seconds if none
specified).
Momentarily short terminals 15-16
to
reset the overload unit. Apply a test current of6x the
overload pickup setting. (Remember the l.5x
factor when
testing with
a single-phase
source). The relay should trip on the
51
function within +/-lOX of the setting.
(9-11
seconds
if
set
at
IO).
If
the required setting is known the final timing
adjustment may be made
using the
time-dial
and
repeating the test.
Overload Unit (49): set the
test
current to 2x
the
pickup
value.
(Remember the 1.5x
factor
when testing with a single-phase
source). Set the overload time-dial to the desired
setting.
(Use #1 dial if none specified). Reset the thermal memory. Apply
the test current. The relay
should
time out within
+/-10%
of the
value
shown on the overload curve 605838 (54 - 66 seconds
if
dial
# I
used).
If
the
required setting
is
known,
the final timing
adjustment
may
be
made
using the
time-dial and retesting.