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CHAPTER 7: TESTING
7.2.3
Ground Fault
Current
Functions
7.2.4
Input
Functions
7.2.5
Thermistor
Input Tests
NOTE
MM3 MOTOR MANAGER 3 – INSTRUCTION MANUAL
Test the ground fault CT (residual / 50:0.025) in a similar manner to phase currents for
accuracy at various injected current levels. To check alarm and trip levels, make the
following settings.
In the
S1 CONFIGURATION
GROUND FAULT CT
INPUT: "RESIDUAL"
In the
S2 PROTECTION
GROUND FAULT ALARM
GROUND FAULT TRIP
LEVEL: "80 %FLC"
In the
S2 PROTECTION
MOTOR PROTECTION THERMAL
FULL LOAD
CURRENT: "100 A"
While displaying the
A1 DATA
injecting current into the 5 A ground fault CT input. The Alarm LED lights and auxiliary relay
1 changes state at 40 A corresponding to the 40% FLC alarm setting. Change the display
back to
GROUND CURRENT
measured ground current reaches 80 A, a ground fault trip occurs. This trip causes the
MM3 Motor Manager 3 to change its indicators and output relay status. The Running LED
turns off, the Tripped and Stopped LEDs turn on, and the contactor A relay de-energizes.
Auxiliary relay 1 remains energized as long as the alarm is present and auxiliary relay 2
energizes after the ground fault trip. The MM3 Motor Manager 3 displays a ground fault trip
message. Turn the ground fault current off and press the reset key to reset the trip.
Operation of each MM3 Motor Manager 3 switch input can be verified on the display. Go to
A3 INPUTS
INPUT CONTACT STATUS
Open and close each switch input and note that the display reflects the present status of
the input terminals. The status is shown as either "OPEN" or "CLOSED".
Begin testing by storing the following thermistor values. In the
menu, set
THERMISTOR
HOT
RESISTANCE: "30 kOHMS"
COLD
RESISTANCE: "0.1 kOHMS"
THERMISTOR
ALARM: "ENABLE"
THERMISTOR
TRIP: "DISABLE"
Place a variable 50 K potentiometer or resistance box across thermistor terminals 17 and
18 as shown in Secondary Injection Test Setup on page 7–2. With the input resistance set to
zero, start increasing the resistance until a thermistor alarm occurs. Verify that the Alarm
LED becomes lit and a
THERMISTOR ALARM
verify that the thermistor resistance agrees with the
The thermistor will have to be removed from the MM3 Motor Manager 3 to accurately
measure its resistance. When the resistance has decreased below the
setpoint value, the alarm will disappear.
To check the thermistor trip function, enable the thermistor trip by making the following
settings changes in the
S1 CONFIGURATION
THERMISTOR
ALARM: "DISABLE"
THERMISTOR
TRIP: "ENABLE"
menu, set:
CT/VT INPUTS
MOTOR PROTECTION GROUND FAULT
LEVEL: "40 %FLC"
MOTOR DATA
GROUND CURRENT
and continue increasing injected secondary current. When the
menu view the status of each input one at a time.
message is displayed. Use an ohmmeter to
THERMISTOR HOT
THERMISTOR
FUNCTIONAL TESTS
menu, set:
menu, set:
actual value, begin
S1 CONFIGURATION
setpoint value.
COLD RESISTANCE
menu:
7–5
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