About the 12M9-006-A4
The 12M9-006-A4 is a CT module for GE Multilin’s MM300 series, a line of motor management relays that protect, control, and monitor low voltage motor systems. The CT module offers a residual ground input, three-phase current metering and thermal overload, undercurrent, and single-phase underpower protection. The phase CTs should be selected so that FLA is no less than 50% of the rated phase CT primary, ensuring maximum accuracy for current measurements performed by the module. 1000 A is the maximum phase CT primary current, and users should take care not to exceed this value.
Ground CT connection can be either a residual connection or a zero sequence installation; however, users should note that only 1 A or 5 A secondary CTs may be used in the case of a residual connection. There is potential for false readings in the event that there is unequal saturation of CTs, CT mismatch, resistance of the power system, issues with motor core saturation density, or issues with the size and location of the motor. GE Multilin’s user manuals provide useful information on reducing the odds of these faulty readings: a wiring connection guide can be found in section 2.2.2.1 of the documents.
Each of the two CTs function as a current source. Users should note that only one ground connection should be established. If two ground connections are established, a parallel path for current will be created to the detriment of the system. Finally, users should only adjust CT wiring when the system is properly de-energized.
