Introduction
2
condition continues until the processing is completed, and the
appropriate delay time has elapsed, the microprocessor issues a
tripping command.
Issuance of the tripping command from the microprocessor sends
a signal from the trip unit to the low-energy, high-speed magnetic
latch in the circuit breaker. The signal in the trip unit counteracts
the permanent magnet in the latch, allowing the latch to trip the
breaker.
Beyond the basic tripping function, the SB Energy-Comm trip unit
also collects real-time data that can be reported via the Siemens
ACCESS System or directly to a personal computer through its
serial port. For any of several functions, the SB Energy-Comm trip
ip
unit can also send an alarm to a remote indicator.
Figure 1.2 Functional Block Diagram
Meter/Communications
Microprocessor
Protective
Microprocessor
Liquid Crystal
Display
Keypad
Test Connector
Rating Plug
SPI
SPI
RAM
PROM
Backlight
PROM
Override
Circuit
Signal
Conditioning
Signal
Conditioning
Power Supply
Frequency
Detection
Analog to Digital
Conversion
Clock
Trip Circuit
Current Inputs
Voltage Inputs
External
Power Supply
Serial Port
RS-232
ACCESS
RS-485
ABCN
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