Protection; Phase Current Inputs - GE MM200 Instruction Manual

CHAPTER 2: INSTALLATION

Protection

Phase current inputs

CAUTION:
MM200 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL
Figure 2-15: Typical phase current input connections
Contactor
A
B
C
To switchgear
ground bus
A10 A9
HI
Control power
A10 A9
LO
Control power
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.
Polarity of the phase CTs is critical for unbalance calculation.
A8
N L
B4
A8 B3 B5 B6
- +
CT1 CT2
Phase current inputs
MM200
Motor Management System
ELECTRICAL INSTALLATION
B7 B8
CT3
888714A2.CDR
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