3-1
!"#$%&'()
!"#$%&'#()*+,-$.&/%&'#
GENERAL
BE1-51/27C Time Overcurrent Relays are microprocessor-based devices that provide voltage control of the
phase time overcurrent function.
BLOCK DIAGRAM ANALYSIS
The following block diagram analysis is referenced to Figures 3-1 and 3-2. A microprocessor (not illustrated
in Figure 3-2) processes signals, performs logic functions, and all of the time overcurrent computations.
Power Supply
Relay operating power is developed by the low burden, flyback switching design, solid-state power supply.
A nominal plus or minus twelve volts dc is delivered to the internal circuitry. Power supply inputs are not
polarity sensitive. A red LED lites to indicate that the power supply is functioning properly.
Type S power supplies use a field adjustable link (J4) to select the appropriate input voltage (either 48 Vdc
or 125 Vdc). Selection is accomplished by placing the link into the desired position (see Figure 3-1). This
link is factory pre-set for 125 Vdc.
Figure 3-1. J4 Link Positioning
Current Sensing
All relay models (except three-phase-and-neutral units) have two sensing ranges for each phase. Each
high/low sensing range has its own set of input terminal connections.
Five ampere CTs have: LOW (0.5 A to 4.0 A) and HIGH (1.5 A to 12.0 A).
One ampere CTs have: LOW (0.1 A to 0.8 A) and HIGH (0.3 A to 2.4 A).
Three-phase-and-neutral sensing units, however, have one of four possible combinations of input sensing
ranges with one range for neutral and one range for the phases.
Five ampere CTs have: 0.5 A to 4.0 A and 1.5 A to 12.0 A.
One ampere CTs have: 0.1 A to 0.8 A and 0.3 A to 2.4 A.
Summary of Contents for BE-51/27C
Page 1: ...0 1 2 3 4 5 67869 ABC DEF G 6H II GGJ KL M DEF DEK...
Page 16: ...BE1 51 27C Controls and Indicators 2 2 Figure 2 1 Location of Controls and Indicators...
Page 20: ...BE1 51 27C Controls and Indicators 2 6...
Page 22: ...BE1 51 27C Functional Description 3 2 Figure 3 2 Functional Block Diagram...
Page 32: ...BE1 51 27C Installation 4 7 Figure 4 10 Typical Internal Diagram Sensing Input Type L...
