Rockwell Automation 1404-M4_M5_M6_M8 Powermonitor 3000 User Manual, Firmware rev. 3.0 or LATER - Manual (Page 164)

164 Publication 1404-UM001F-EN-P - November 2009
Chapter 8 Advanced Features
Each data point is expressed in calibrated analog-to-digital (A/D)
converter counts with a resolution of 8192 (13-bit w/sign) or 128 (7-bit
w/sign). A client may calculate the primary-side instantaneous voltage
or current magnitude of each data point by using the following
formula:
Where:
•
M
i
= instantaneous value of the voltage or current data point
•
M
(max rms)
= max rms magnitude
= 399.0 line-to-neutral volts for channels 1, 3, and 5
= 691.1 line-to-line volts for channels 1, 3, and 5
= 10.6 amperes for channels 2, 4, 6, and 7
•
R
max
= maximum resolution
= 8192 for 13-bit w/sign, capture types 0, 1, and 2
= 128 for 7-bit w/sign, capture types 3, 4, and 5
•
N
t
= PT or CT ratio
= PT or CT primary / PT or CT secondary
•
M
data
= value of the data point from the Oscillograph
Configuration/Read-back Data Select table
For example, consider the following capture:
•
PT primary = 13.8 kV
•
PT secondary = 120 V
•
CT primary = 100 A
•
CT secondary = 5 A
•
Delta voltage mode (line-to-line)
•
Capture type = 2
You would multiply each data point by the following factor to
correctly display the waveform:
M
i
M
max rms ( )
2 •
R
max
-------------------------------------- N
t
M
data
• • =
Factor 691.1 1.414 • ( ) 8192 ⁄ 13800 120 ⁄ ( ) • 13.72 = =