71M6513/71M6513H Demo Board User’s Manual
Page: 41 of 112
©
2005-2006 TERIDIAN Semiconductor Corporation
Revision 5.6
The neutral current is available for display. The help text for the MR command describes how to display neutral
current on the display. For the "M" command of the CLI for current, phase 4 signifies the neutral current.
The accuracy data collected for several
ALT_MUX_RATE
settings is given in Table 1-14:
Test
Number
Applied
Current
measured
current
error [%]
measured
current
error [%]
measured
current
error [%]
1
200
200.66
0.33
201.15
0.575
202.335
1.168
2
150
150.63
0.42
150.778
0.519
150.824
0.549
3
100
99.82
-0.18
99.765
-0.235
100.221
0.221
4
50
49.859
-0.282
49.76
-0.48
49.333
-1.334
5
25
24.889
-0.444
24.861
-0.556
24.951
-0.196
6
10
10.042
0.42
10.134
1.34
10.193
1.93
7
5
4.988
-0.24
5.132
2.64
5.155
3.1
8
2.5
2.486
-0.56
2.459
-1.64
2.535
1.4
9
1
1.036
3.6
1.067
6.7
1.071
7.1
10
0.5
0.564
12.8
0.581
16.2
0.592
18.4
11
0.25
0.324
29.6
0.328
31.2
0.334
33.6
ALT_MUX_RATE = 10
(252Hz)
ALT_MUX_RATE = 25
(100Hz)
ALT_MUX_RATE = 50
(51Hz)
Table 1-14: Neutral Current Accuracy at Various Sampling Frequencies
MPU (XDATA) address 0x027 represents the neutral current (RMS value). For the standard Demo Code
(revision 3.04), this address is a reserved location.
In the CE interface, the CE address 0x56 represents the 32-bit neutral current value, I3SQSUM. It has different
units than the current registers derived from the regular inputs IA, IB, and IC, because it is sampled at a
different rate (default = 1/10) than the other current channels, and because the reference is not VREF, but
VBIAS.
If one accumulates data for 250 samples (with XDATA address 0x0F=10) the accumulated data is transferred to
the MPU as one register on each XFER_BUSY interrupt. The values in between samples are equivalent to the
previous acquired sample value.
The actual LSB value for the neutral current measurement is computed from the following formula
h
A
N
IMAX
LSB
ACC
NC
2
3
2
10
431
⋅
⋅
⋅
=
where:
IMAX is the numerical value of the current corresponding to 176mV RMS at the IC input,
NACC is the product of
SUM_CYCLES
and
PRE_SAMPS
,
With IMAX = 208A and N
ACC
= 2520, LSB
NC
becomes 39.8*10
-6
/A
2
h.
http://www.datasheetcatalog.com/
