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7.2 FUNCTIONAL TESTS
7.2 FUNCTIONAL TESTS
Any phase current protection is based on the ability of the MM3 to read phase input currents accurately. Make
the following settings:
S2: PROTECTION \ MOTOR PROTECTION THERMAL \ FULL LOAD CURRENT = 100A.
S1: CONFIGURATION \ STARTER \ STARTER TYPE = FV NON REVERSING.
To determine if the relay is reading the proper input current values, inject different phase currents into the CT
inputs and view the current readings in A1: DATA \ MOTOR DATA. The displayed current should be equal to the
actual injected current.
Phase current values will be displayed even if the motor status is stopped; that is, contactor A has not been
activated by a start command. Very low currents are displayed as 0 A.
Once the accuracy of the phase CT inputs has been established, various phase alarm and trip condition tests
can be performed by altering setpoints and injected phase currents.
To simulate an overload condition, enter S2: PROTECTION \ MOTOR PROTECTION THERMAL and alter and store
OVERLOAD CURVE NUMBER = 4 and FULL LOAD CURRENT = 50A. PHASE CT PRIMARY AMPS should be set to 100A.
Close the start A input and note that the RUNNING LED goes on. Inject a current of 10 A into all three phases.
The relay will display a current value of:
displayed current = actual injected current × 100/5 = 10 × 100 / 5 = 200 A.
This represents 4 times the phase FULL LOAD CURRENT setpoint. Therefore, based on a 400% overload and
curve #4, Contactor A will change state 23 seconds after the overload is first applied. When this occurs, the
Running LED turns off and the Tripped and Stopped LEDs are lit. After the trip has occurred, use the A1: DATA \
MOTOR DATA actual values to verify that the thermal capacity used is now 100%. Press the
the MM3.
To prepare the MM3 to simulate an unbalance alarm, make the following settings:
S2 PROTECTION \ MOTOR PROTECTION OPTIONS \ PHASE UNBALANCE ALARM = ENABLE
S4 CONTROL \ AUX RELAY 1 CONFIG \ AUX RELAY 1 FUNCTION = ALARMS
S4 CONTROL \ AUX RELAY 2 CONFIG \ AUX RELAY 2 FUNCTION = TRIPS
Inject 5.0 A into all three phase CTs. The MM3 displays a balanced phase current of 100 A for each phase.
While still viewing actual values, slowly begin decreasing phase 1 current until the UNBALANCE ALARM mes-
7
sage comes on. AUX Relay 1 should energize when the alarm is present. Unbalance is calculated as follows:
For average currents greater than motor full load:
I
I
–
>
n
av
15% (alarm)
---------------- -
I
av
For average currents less than the motor full load:
I
I
–
>
n
av
15% (alarm)
---------------- -
I
fl
where: I
= RMS current in any phase with maximum deviation from the average current I
n
I
= average of the 3 phase currents
av
I
= motor full load current
fl
I
= phase A current
a
I
= phase B current
b
I
= phase C current
c
7-2
30% trip
I
30% trip
,
with
a
I
=
------------------------ -
av
MM3 Motor Manager 3
7.2.1 PHASE CURRENT FUNCTIONS
I
I
+
+
b
c
3
7 TESTING
RESET
key to reset
av
GE Power Management
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