Rockwell Automation 193/592-EC1/EC3/EC5 E3 and E3 Plus Solid-State Overload Relay - Quick Reference - Manual (Page 11)

11
Publication 193-QR003B-EN-P - October 2009
External Current Transformer Application (Cat. No. 193-EC_ZZ)
E3 and E3 Plus Overload Relays (Cat. No. 193-EC_ZZ) are designed for use with separately
mounted, customer-supplied current transformers (CTs) as required in higher-current
applications. The FLA setting range is 9…5000 A for these units, with a legal setting range
per the user’s manual. Parameter 78, CT Ratio, is provided for setting the current transformer
ratio to be installed.
Current Transformer Specifications
The 193-EC_ZZ Overload Relays are intended for use with a CT having a secondary current
rating of 5 A. The installer shall provide one CT for each motor phase and shall connect the
CT secondary leads to the appropriate E3 Overload Relay power terminals as shown in Figure
7: on page 13. The CT shall have an appropriate ratio rating as detailed in the user’s manual.
Additionally, the CT shall be selected to be capable of providing the required VA to the
secondary load, which includes the E3 Overload Relay burden of 0.1 VA at the rated
secondary current and the wiring burden.
Finally, the CT shall be rated for protective relaying to accommodate the high inrush currents
associated with motor startup and shall have an accuracy of
≤ ±2% over its normal operating
range.
IMPORTANT
Parameter 27, Single/Three Ph, should be set to single-phase for
single-phase devices and three-phase for three-phase devices.
IMPORTANT
In single-phase devices, traditional single-phase wiring (connecting
T2 to L3) will result in a vector imbalance of current flowing through
the E3 Plus Overload Relay. This will result in inaccurate ground fault
reporting and protection.
ANSI (USA) Class C5 B0.1
CSA (Canada) Class 10L5
IEC (Europe) 5 VA Class 5P10
IMPORTANT
The improper selection of a current transformer can result in the E3
Overload Relay reporting inaccurate motor operational data and
possible motor damage. The selected current transformer must be
rated for protective relaying applications.