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THREE PHASE POWER/ENERGY METERING MODULE
PULSE OUTPUT
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7184
PDS038-SA9105-002
Rev. A
07-01-97
FEATURES
n
Performs one, two or three phase power
and energy measurement
n
Meets the accuracy requirements for
Class 1 AC Watt hour meters
n
Operates over a wide Temperature
Range
n
Uses current transformers for current
sensing
n
Three pulse rate outputs available
n
Protected agianst ESD
SA9105 APPLICATION NOTE
PM9105AP
DESCRIPTION
The SAMES three phase power/energy metering module, the PM9105AP provides three
pulse rate output options, the frequency of which are proportional to the active power
consumption.
Energy consumption can be determined by the power measurement being integrated
over time.
The method of calculation takes the power factor into account.
The output of this innovative universal three phase power/energy metering circuit is
ideally suited for energy calculations in applications using a -controller or mechanical
counter.
The application utilises the SAMES SA9105APA, SA9105EPA or SA9105FPA three
phase power metering integrated circuits for power measurement.
The module is supplied configured to operate on 3 x 230V, 3 x 80A mains system. This
can be adapted to operate on 3 x 115V, 3 x 80A mains system. Please refer to the resistor
selection table shown at the end of the Application Circuit parts list.
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BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS *
Parameter
Symbol
Min
Max
Unit
Supply Voltage (Note 1)
V
AC
540
V
Storage Temperature
T
STG
-25
+125
C
Operating Temperature (Note 2)
T
O
-10
+70
C
Note 1:
Voltages are specified with reference to Neutral.
Note 2:
The SA9105 integrated circuit is specified to operate over the temperature
range -10C to +70C. The module functionality will however depend upon
the external components used.
* Stresses above those listed under "Absolute Maximum Ratings" may cause permanent
damage to the device. This is a stress rating only. Functional operation of the device
at these or any other conditions above those indicated in the operation sections of this
specification, is not implied. Exposure to Absolute Maximum Ratings for extended
periods may affect device reliability.
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ELECTRICAL CHARACTERISTICS
(Over the temperature range -10C to +70C, unless otherwise specified.
Parameter
Symbol
Min Typ
Max Unit
Condition
Supply Voltage (x3 Phases)
V
AC
180
230
265
V
PM9105APE
(Continuous)
Frequency Output
FOUTX
Refer to applicable IC data sheet
Power Consumption
1
100
m W V
DD
= 5V
Note 1:
Power consumption specifications exclude power consumed by the current
sensors.
CONNECTION DESCRIPTION
Designation
Description
PL5
Voltage Supply connected to Phase 1
Voltage Supply connected to Phase 2
Voltage Supply connected to Phase 3
Voltage Supply connected to Neutral Line (Common)
PL6
Power Output: 4Hz at rated current
Power Output: 290 Hz at rated current
Power Output: 1160 Hz at rated current
0V (Common)
PL4
5V DC Supply Voltage
0V DC Supply Voltage
CT1
Phase 1 (Direction indicated on PCB)
CT2
Phase 2 (Direction indicated on PCB)
CT3
Phase 3 (Direction indicated on PCB)
FUNCTIONAL DESCRIPTION
1.
Power Calculation
In the Application Circuit (see Figure 2), the output currents from the current sensors
will be between 0 and 16A. The current input stages saturate at input currents
greater than 18A
RMS
. The mains voltage (mains voltage + 15% - 20%) is used for
the power calculation, together with the current information from the current sensors
(current transformers).
The calculated power for the 3 phases is integrated over time and converted into a
corresponding frequency.
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For rated conditions, the signals into the current and voltage sensor inputs are set
as follows:
Current sensor input currents:
16 A
RMS
Voltage sensor input currents: 14 A
RMS
Under these conditions, the device generates a pulse rate of 1.16kHz at output
FOUT1.
2.
Electrostatic Discharge (ESD) Protection
The device's inputs/outputs are protected against ESD. The modules resistance to
transients will be dependant upon the protection components used.
3.
Power Consumption
The overall power consumption rating for this power metering application (Figure
2), is under 500mW, excluding the current sensors.
4.
Isolation
The reference for the unit is connected to neutral.
5.
Circuit Description
The module is supplied from an external 5V DC supply.
The Application Circuit (figure 2), details the components required for a three phase
power metering module. Terminated current transformers are used as current
sensors.
The most important external components are:
C
7
, C
9
, C
10
and C
11
are the outer loop capacitors for the integrated oversampling
A/D converters. The typical value of C
7
is 2.2nF and the value of C
9
, C
10
and C
11
is
560pF.
The actual values determine the signal to noise and stability performance. The
tolerances should be within 10%.
C
4
, C
5
, C
6
and C
8
are the inner loop capacitors for the integrated oversampling
A/D converters. The typical value of C
4
, C
5
, C
6
and C
8
is 3.3nF. Values smaller than
0.5nF and larger than 5nF should be avoided.
Terminated current sensors (current transformers) are connected to the current
sensor inputs of the SA9105 through current setting resistors (R
8
..R
13
).
The resistor values should be selected for an input current of 16
A into the SA9105
at the rated line current.
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The values of these resistors should be calculated as follows:
Phase 1:
R
8
= R
9
= (I
L1
/16
A) x R
18
/2
Phase 2:
R
10
= R
11
= (I
L2
/16
A) x R
19
/2
Phase 3:
R
12
= R
13
= (I
L3
/16
A) x R
20
/2
Where I
LX
=
Secondary CT current at rated conditions.
R
18
, R
19
and R
20
=
Termination resistors of the three current transformers.
R
1
+ R
1A
, R
4
and R
15
set the current for the phase 1 voltage sense input. R
2
+ R
2A
,
R
5
+ P
5
and R
16
set the current for phase 2 and R
3
+ R
3A
, R
6
+ P
6
and R
17
set the current
for Phase 3. The values should be selected so that the input currents into the voltage
sense inputs (virtual ground) is set to 14
A at nominal line voltage. Capacitors C1,
C2 and C3 are for decoupling and phase compensation.
R
14
+ P
14
defines all on-chip bias and reference currents. With R
14
+ P
14
= 24k
,
optimum conditions are set. P
14
may be varied within 10% for calibration purposes.
Any changes to R
14
will affect the output quadratically (i.e:
R = +5%,
FOUT =
+10%).
XTAL is a colour burst TV crystal (f = 3.5795 MHz) for the oscillator. The oscillator
frequency is divided down to 1.7897 MHz on-chip to supply the digital circuitry and
the A/D converters.
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