84-28 9424200996
Settings Calculation Examples BE1-11m
Figure 84-33. General Settings, Display Units Screen
Style Number
The BE1-11m style number shown in Figure 84-34 is used in this application example. The style number
is defined below.
Figure 84-34. BE1-11 Style Number
M ......... Application Option ...................... Motor
6 .......... Phase CT Option ........................ CT1 - 5 Amp Nominal / CT2 - 5 Amp Nominal
D .......... Ground CT Option ...................... CT1 - 5 Amp Nominal / CT2 - 5 Amp Nominal
2 .......... Power Supply Option ................. 125/250 Vac/dc
M ......... RS-485 Port Protocol ................. Modbus™
1 .......... Ethernet Protocol ....................... BESTnetPlus Only
J .......... Case Option ............................... Vertical Case
2 .......... Alarm Contact Option ................. Normally Closed (closes upon power removal / watchdog failure)
P .......... Option 1 ...................................... Phase Differential
0 .......... Network Connections ................. Copper
E .......... Language ................................... English
0 .......... Option 2 ...................................... None
00 ........ Firmware Option ......................... Latest Release
System Parameters - Sensing Transformers
Phase CT Ratios
The motor manufacturer data for full-load amps (FLA) is 205 A under normal running conditions. Select
phase CTs so that the FLA is 50 percent or greater of the rated phase CT primary current. To minimize
CT saturation, select the phase CT primary current so the FLA is 100 percent of the phase CT primary or
slightly less, never more. IEEE states that “CT saturation is minimized by keeping burdens low (especially
the dc resistive component), by using high-ratio current transformers, and by selecting current
transformers with a high knee-point (saturation) voltage.” (IEEE Std C37.96-2000, IEEE Guide for AC
Motor Protection).
Select CTs with a primary rating of 300 A; then the ratio with 5A CTs used in this application example is
60 (300:5). The secondary current measured by the BE1-11m is 3.41 A (205 A ÷ 60) when the motor is at
full load. CTs with an accuracy class of C100 and greater provide a satisfactory knee-point voltage for the
motor FLA. Enter 60 for the CT ratios on the System Parameters, Sensing Transformers screen shown in
Figure 84-35. Use Wye CT connections for low burden.
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