Teridian 71M6403, Manual

Page: 61 / 75

71M6403
Electronic Trip Unit
SEPTEMBER 2006
Page: 61 of 75
©
2006 TERIDIAN Semiconductor Corporation
REV 1.0
Processed Current Data
Processed current data is available in CE addresses 0x4A through 0x4F, as listed below:
Output
Register
CE Address Description
I0SQSUM_X 0x4A LSB = (IMAX/ln8)
2
* 3.3335*10
-8
A
2
peak
I1SQSUM_X 0x4B LSB = (IMAX/ln8)
2
* 3.3335*10
-8
A
2
Peak
I2SQSUM_X 0x4C LSB = (IMAX/ln8)
2
* 3.3335*10
-8
A
2
Peak
I3SQSUM_X 0x4D LSB = (IMAX/ln8)
2
* 3.3335*10
-8
A
2
Peak
I4SQSUM_X 0x4E LSB = (IMAX/ln8)
2
* 3.3335*10
-8
A
2
Peak
I5SQSUM_X 0x4F LSB = (IMAX/ln8)
2
* 3.3335*10
-8
A
2
Peak
The CE writes the output data into the I0SQSUM_X, I1SQSUM_X etc. registers at the end of each accumulation interval.
The values for IXSQSUM_X are based on the formula:
∑
+
=
1 _
0
_
CNT STR
IXSQ X IXSQSUM
Overcurrent Detection
The main task in circuit breaker applications is to detect an over-current situation as quickly as possible and to apply the tripping
procedures. The CE firmware has an integrated comparator function that helps to verify each measured sample with reference to
the value stored in the
FAULT_THRESH register at address 0x2F. If a sample above the programmed FAULT_TRHESH is
encountered in one of the input signals I0, I1, I2 or I3, the FAULT_PULSE is generated on the DIO7 pin. This pin should be
configured by the MPU to be an output pin and should be internally set to generate an interrupt in order to initiate the necessary
routines of the circuit breaker application firmware. The process for generating the FAULT_PULSE from encountering a sample
above the programmed threshold can be less than 400µs.
CE Register CE Address Description
FAULT_THRESH 0x2F LSB = (IMAX/ln8) * 5.5719*10
-9
A peak
STR_CNT 0x31 STROBE_PULSE =
(
STR_CNT + 1) * 3.9673*10
-4
s
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