CHAPTER 2: INSTALLATION ELECTRICAL INSTALLATION
MM200 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL 2–13
Protection
Phase current inputs Figure 2-15: Typical phase current input connections
The MM200 has three channels for phase current inputs, each with an isolating
transformer. The phase CTs should be chosen so the FLA is not less than 50% of the rated
phase CT primary. Ideally, the phase CT primary should be chosen such that the FLA is
100% of the phase CT primary or slightly less, never more. This will ensure maximum
accuracy for the current measurements. The maximum phase CT primary current is
1000 A.
The MM200 measures up to 8 times the phase current nominal rating. CTs with 1 A or 5 A
secondaries must be used if the FLA is greater than 5 A. The chosen CTs must be capable
of driving the MM200 phase CT burden.
CAUTION:
Polarity of the phase CTs is critical for unbalance calculation.
A
C
B
Contactor
B3
B4
B6B5
Phase current inputs
MM200
Motor Management System
To switchgear
ground bus
888714A2.CDR
B7
B8
CT1 CT2 CT3
Control power
+
-
A10
A9
A8
Control power
N
L
HI
A10
A9
A8
LO
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