PM2002 Sames, PM2002 Datasheet - Page 3

• Manufacturer Part Number: PM2002
• Description: Energy Meter Evaluation Module
• Manufacturer: Sames

ANALOG SECTION
The analog (metering) interface described in this section is
designed for measuring 220V/80A with precision better than
Class 1.
The most important external components for the SA2002D
integrated circuit are the current sense resistors, the voltage
sense resistors and the bias setting resistor. The resistors
used in the metering section should be of the same type so
temperature effects are minimized.
Voltage Input IVP
The voltage input of the SA2002D (IVP) is driven with a current
of 14µA at nominal mains voltage. This voltage input saturates
at approximately 17µA. At a nominal voltage current of 14µA
allows for 20% overdriving. The mains voltage is divided with a
voltage divider to 14V that is fed to the voltage input pins via a
1M resistor
Voltage Divider
The voltage divider is (Figure 3) calculated for a voltage drop of
14V. Treat C7 as a short circuit and ignore J16. Equations for
the voltage divider in figure 3 are:
Combining the two equations gives:
Values for resistors R10 = 47 , R11 = 22k , P1=10k
R12 = 1M is chosen.
Substituting the values result in:
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PM2002DP
RB = R1 + R2 + R3 + R15 + R10
RB = R12 || ( R11 + P1 / 2)
(RA + RB) / 220V = RB / 14V
RB = 26.29k
RA = RB x (220V / 14V - 1)
RA = 386.84k
NEUTRAL
LIVE IN
R10
R1
Figure 3: Mains voltage divider
R2
and
3/10
R3
Standard resistor values of R1, R2, R3 and R15 are chosen to
be 47k , 150k , 47k and 150k . The resistor RA is divided
so that the voltage drop across one resistor is within the
specified limits of the resistor type that is used, usually
200VDC. The resistor value ratios are chosen so that shorting
J16 the module could be used on a 110VAC mains system.
CURRENT SENSOR INPUT RESISTORS FIGURE 4 (USING
A SHUNT RESISTOR)
The resistors R6, R7 define the current level into the current
sense inputs the device. The voltage drop across the shunt
should be at least 20mV at rated conditions. A shunt resistor
with a value of 50mV @80A was chosen for the application
module for its ease of use. The resistor values are calculated
for an input current of 16µA on the current inputs at rated
conditions. For a 80A meter the resistor values are calculated
as follows:
R6 = R7 = (I / 16µA) x R / 2
I Line current
A standard value of 1.6k is chosen.
L =
LIVE IN
LIVE OUT
J16
= 80A / 16µA x 625u / 2
= 1.5625k
L
R15
Figure 4: Current input configuration
R11
SH
P1
R14
L
C7
R12
R6
R7
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