Inputs And Outputs; Phase Ct Inputs; Ground Fault Ct Input; Supply Voltage - GE MOTOR MANAGER 2 Instruction Manual

2 INSTALLATION

2.2 INPUTS AND OUTPUTS

Both 5 A and 1 A current transformer secondaries are accommodated by the MM2. Each phase cur-
rent input to the MM2 has 3 terminals: 5 A input, 1 A input, and the common input. For example, if the
phase CTs are 200:5, connect phase 1, 2, and 3 CT secondaries to terminals 1/3, 4/6, and 7/9,
respectively. For motor full-load currents up to 10 A, the phase conductors can be direct connected
to the MM2 with no phase CTs required providing that the voltage at the CT terminals does not
exceed 600 V RMS.
CTs should be selected to be capable of supplying the required current to the total secondary load
which includes the MM2 relay burden of 0.1 VA at rated secondary current and the connection wiring
burden. The CT must not saturate under maximum current conditions which can be up to 8 times
motor full load during starting.
The ground CT has a 5 A input, a 50:0.025 input, and a common input. The 5 A input on the ground
CT is used for 5 A secondary CTs or for residual connection of phase CTs. Residual ground fault pro-
tection provides a sensitivity of 5% of motor Phase CT Primary. The 50:0.025 core balance (zero-
sequence) CT input can be used for improved sensitivity when measuring the ground fault current.
Care must be taken when turning ON the Ground Fault Trip feature. If the interrupting
device (contactor or circuit breaker) is not rated to break ground fault current (low resistance
or solidly grounded systems), the feature should be disabled. The 50:025 input is only rec-
NOTE
ommended to be used on resistance grounded systems. Where the system is solidly
grounded or high levels of current are to be detected use the 5 A ground input.
Supply voltage of 120/240 V AC, 50 or 60 Hz, is required to power the MM2. The label on the back of
the unit will specify the voltage which has been internally set inside the MM2. To change the voltage
setting, open the sliding door on the back of the MM2 and locate the supply voltage selector slide
switch. The selector slide switch has a label affixed to show the 120/240 V AC positions. Set the slide
switch to the desired voltage.
This is an additional ground terminal provided for dissipating transient signals and surges. This must
be connected by a thick wire or braid to the system ground for reliable operation.
Signal wiring is to box terminals that can accommodate wire as large as 12 gauge. CT connections
are made using #8 screw ring terminals that can accept wire as large as 8 gauge. Consult Figure 2–
4: TYPICAL WIRING DIAGRAM on page 2–3. Other features can be wired as required.
GE Power Management
MM2 Motor Manager 2
2.2 INPUTS AND OUTPUTS

2.2.1 PHASE CT INPUTS

2.2.2 GROUND FAULT CT INPUT

2.2.3 SUPPLY VOLTAGE

2.2.4 GROUND SURGE

2.2.5 EXTERNAL CONNECTIONS

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