2–10 MM300 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL
ELECTRICAL INSTALLATION CHAPTER 2: INSTALLATION
Figure 11: CBCT connection
CAUTION:
The zero-sequence connection is recommended. Unequal saturation of CTs, size and
location of motor, resistance of power system, motor core saturation density, and
other factors, may cause false readings in the residually connected ground fault
circuit.
NOTE:
Only one ground input should be wired; the other input should be unconnected.
The exact placement of a zero-sequence CT to detect only ground fault current is shown
below. If the core balance CT is placed over shielded cable, capacitive coupling of phase
current into the cable shield during motor starts may be detected as ground current unless
the shield wire is also passed through the CT window. Twisted-pair cabling on the zero-
sequence CT is recommended.
A
C
B
Contactor
–
+
–
C–+
CPU module
MM300
Motor Management System
To switchgear
ground bus
853711A1.CDR
R
ISG
RS485 Thermistor CBCT
Control power
LN
+
SG = Surge Ground = Functional Ground
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