Manual

Rockwell Automation Publication 1425-UM001A-EN-P - January 2012 39
Software Interface Chapter 3
Interval Energy Usage Data (Register 28 …48)
Energy is integrated over a user-selectable recording time interval. Refer to
Recording Interval Time (Register 53)
.
The interval energy usage values are calculated over the recording interval. At the
end of each recording interval, the values are stored in the interval energy
registers. The recording interval timestamp indicates the time at the end of the
recording interval.
Interval real and reactive energy values are expressed in a signed 16-bit INT
register with a raw value range of -32,768…32,767. Interval apparent energy
values are similarly expressed in an unsigned INT with a raw value range of
0…65,535. The raw value is the value before the scaling factor is applied.
With certain combinations of load and interval time, the interval energy may
exceed the range of the registers. In this case the registers will roll over (like a car
odometer) and report incorrect interval energy. The tables below list calculated
interval energy register raw values at various percentages of nominal phase
current (Ipn) and nominal voltage for the particular power monitor model
(240V or 480V) and 100% power factor. Values in bold font in the tables indicate
where a value rollover is likely to occur.
We recommend that you adjust the interval to a shorter time period to avoid this
issue.
Table 2 0
lists real or reactive energy values (one phase/sum of phases) at varying
percent of nominal phase currents with nominal voltage 240V or 480V for SP2
model and 100% power factor (0% power factor for reactive energy).
Table 20 - Real or Reactive Interval Energy Raw Values
Load Current 25% Ipn 50% Ipn 100% Ipn 120% Ipn
Interval Time (min)
5 1600 / 4800 3200 / 9600 6400 / 19200 7680 /23,040
6 1920 / 5760 3840 / 11,520 7680 / 23,040 9216 /27,648
10 3200 / 9600 6400 / 19,200 12,800 / 38,400 15,360 / 46,080
12 3840 / 11,520 7680 / 23,040 15,360 / 46,080 18,432 / 55,296
15 4800 / 14,400 9600 / 28,800 19,200 / 57,600 23,040 / 69,120
20 6400 / 19,200 12,800 / 38,400 25,600 / 76,800 30,720 / 92,160
30 9600 / 28,800 19,200 / 5,7600 38,400 / 115,200 46,080 / 138,240