ADE9000 Technical Reference Manual
UG-1098
Rev. 0 | Page 19 of 86
AVARHR_HI and AFVARHR_HI registers indicates whether
the energy is negative or positive.
Other accumulation modes offered include positive only
accumulation mode with VARACC[1:0] equal to 10, and
negative only accumulation mode (where only negative reactive
energy is accumulated) with VARACC[1:0] equal to 11.
No-Load Detection
No-load detection prevents energy accumulation due to noise,
when the input currents are below a given meter start current.
To determine if a no-load condition is present, the
evaluates if the accumulated energy is below a user defined
threshold over a user defined time period, which is done on a
per phase and per energy basis.
The NOLOAD_TMR[2:0] bits in the EP_CFG register determine
whether to evaluate the no-load condition over 64 samples to 4096
samples, 64/8 ksps = 8 ms to 512 ms, by writing to the bits in the
EP_CFG register, as described in Table 15. No-load detection is
enabled by default, over the minimum time of 64/8 ksps = 8 ms.
No-load detection is disabled when the NOLOAD_TMR[2:0] bits
in the EP_CFG are equal to 111 (binary).
Table 15. No-Load Condition Evaluation Time
NOLOAD_TMR[2:0]
Samples to
Evaluate No
Load Over
Time that No-Load
Detection is
Evaluated Over
0 64
8
ms
1 128
16
ms
2 256
32
ms
3 512
64
ms
4 1024
128
ms
5 2048
256
ms
6 4096
512
ms
7
No-load disabled
No-load disabled
The user defined no-load thresholds are written into the
ACT_NL_LVL, REACT_NL_LVL, and APP_NL_LVL registers.
The ACT_NL_LVL register sets the no-load threshold for total
and fundamental active energy. Correspondingly, the
REACT_NL_LVL register sets the no-load threshold for total
and fundamental reactive energy while the APP_NL_LVL sets
the no-load threshold for total and fundamental apparent energy.
The no load thresholds are calculated according to the following
equation:
X
SCALE
FULL
xWATT
LVL
xNL
64
_
_
_
where:
xWATT_Full_Scale
is the nominal xWATT value with full-scale
inputs, 20,694,066. Note that xVAR and VA have the same
scaling; therefore, the same value can be used for all three
thresholds.
X
is the desired no-load input power level. For example, to set the
no-load threshold to zero out energy below 50,000 from full scale,
X = 50,000 in the previous equation.
Then, for a 50,000:1 no-load threshold level, xNL_LVL is
0x6804:
0x6778
488
,
26
50000
64
066
,
694
,
20
_
LVL
xNL
When a phase is in no-load, every f
DSP
= 8 ksps, zero energy is
accumulated into the energy registers and CF accumulation.
Note that the x_ACC registers are not affected by no-load
detection. Even when in no-load, any power calculated in the
respective xWATT, xVAR, and xVA registers is accumulated
into the corresponding x_ACC register every f
DSP
= 8 ksps.
No-Load Indications
The PHNOLOAD register indicates whether each phase of
energy is in no-load. For example, the PHATNL[2:0] bits in
the PHNOLOAD register indicate whether the Phase A total
apparent energy, reactive energy, and active energy are in phase
on Bit 2 through Bit 0, respectively. If a bit is set, it indicates that
the phase energy is in no-load; if it is clear, the phase is not in
no-load.
The user can enable an interrupt to occur when one of the per
phase energy no-load status changes, either going into or out of
no-load. There is an interrupt enable bit for each type of energy.
Set the VAFNOLOAD, RFNOLOAD, AFNOLOAD, VANLOAD,
RNLOAD, and ANLOAD bits in the STATUS1 register to
enable an interrupt on IRQ1 when one or more phases of
fundamental VA, fundamental VAR, fundamental watt, total
VA, total VAR, and total watt no-load changes status.
There is also an option to indicate the no-load status on the
EVENT pin; see the Interrupts/EVENT section for more
information.
Figure 22 shows what happens when the xWATT, low-pass
filtered watt, value goes above the user configured no-load
threshold and then back down below it again. The same concept
applies to all of the energy values (total and fundamental VAR,
total VA) with the corresponding REACT_NL_LNL and
APP_NL_LVL no-load thresholds.
LOW-PASS
FILTERED
ACTIVE POWER (xWATT)
ACTIVE ENERGY
NO LOAD THRESHOLD
(ACT_NL_LVL)
NO LOAD ACCUMUL ATION INTERVAL IS
SET IN EP_CFG.NOLOAD_TMR
ACTIVE ENERGY
NO LOAD ACCUMULATOR
NO LOAD INDICATION
STATUS1.ANOLOAD)
ACTIVE ENERGY,
xWATTHR
15
52
3-
02
2
Figure 22. No-Load Detection and Indication
