Datasheet

78M6610+PSU Data Sheet
2.4 Fundamental and Harmonics Calculations
Fundamental and Harmonics
The 78M6610+PSU provides measurements on fundamental and total harmonic of voltage, current, and
power (active, reactive, and apparent).
SINE(t)
V
X
X
COSINE(t)
SINE(t)
i
X
X
COSINE(t)
VSINE
VCOS
ISINE
ICOS
Vfund
Ifund
Vrms
Vharm
Iharm
N
N
N
N
∑
N-1
n=0
∑
N-1
n=0
∑
N-1
n=0
∑
N-1
n=0
X
2
+ Y
2
X
Y
X
2
+ Y
2
X
Y
X
2
- YI
2
X
YI
X
2
- YI
2
X
YI
Irms
Figure 2-5: Voltage and Current Fundamental and Harmonic Calculations
Fundamental and Harmonic Selection
The 78M6610+PSU allows extraction and calculation of a single selected harmonic. By default, the
fundamental (first harmonic) is selected for voltage, current, active, reactive real and apparent power
calculations. The HARM register is used to select the single harmonic to extract.
By setting the value in the HARM register to a higher harmonic, the fundamental result registers will
contain amplitudes of the selected harmonic. In this case the harmonic result register will contain the
balance of the voltage, current, or power.
2.5 Accumulation Interval
The accumulation interval mode is configurable by the user through the Accum and AccumCyc registers
and the status of the line lock bit.
The ACCUM register contains an unsigned integer values representing the accumulation interval (time)
expressed in number of high-rate samples.
The accumulation interval can also be locked to the incoming line voltage cycles. The LINELOCK bit
in the command register allows the accumulation interval to be determined by the ACCUM register or
to be locked to the line cycle.
Once locked to the line cycle the accumulation interval will end after the first low-to-high zero
crossing of the Reference AC Voltage (see Zero-Crossing Detection) input occurs once the Minimum
Accumulation time has elapsed. The Actual Accumulation Interval will span an integer number of line
cycles. When LINELOCK is not set, the Accumulation Interval will equal the value set by the ACCUM
register.
The effective sample rate for each input of the 78M6610+PSU is 4KS/s. The DIVISOR register
reports the actual number of samples within any given accumulation interval.
Rev 3 13