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SA9605ASA

THREE PHASE POWER/ENERGY METERING IC WITH INSTANTANEOUS PULSE OUTPUT

South African Micro Electronic Systems 

SA9605A

The frequencies shown in the above table were chosen to allow a 4 - 3 - 2 scaling ratio

for rated conditions. This facility provides ease of interface with applications which use

the same post divider with mechanical counter or unchanged microcontroller software

for different current rated kWh meters.

For example, a meter manufacturer may wish to build meters for 3 system configurations

with rated current loading of 80A , 60A and 40A . The rated line voltage is

RMS

RMS

RMS

230V .

RMS

FOUT1 Frequency

Consider the case where FOUT1 is the output of the energy counting block. For each

of the three rated conditions, the input current sensing resistors are chosen to ensure that

16µA flows into the current sensing pins.

RMS

Case 1

I = 80A

L

RMS

1 pulse on FOUT1 =

80 * 230 * 3

1160

= 47.6Ws

Case 2

I = 60A

L

RMS

1 pulse on FOUT1 =

60 * 230 * 3

1160

= 35.7Ws

Case 3

IL = 40ARMS

1 pulse on FOUT1 =

40 * 230 * 3

1160

= 23.8Ws

The amount of energy represented by one pulse for each of the three cases is different.

In addition to changing the current sensing resistor network, the energy counting block

must also be altered.

FOUT2 Frequency

Now consider the advantage of the user selectable frequency available on FOUT2.

Again the input current sensing resistors must be chosen to ensure that 16µA flows

RMS

into the current sensing pins.

Case 1

Case 2

Case 3

8/14

I = 80A , PGM1 = 0 PGM0 = 0

L

RMS

1 pulse on FOUT2 =

80 * 230 * 3

5.11

= 10.8kWs

I = 60A , PGM1 = 0 PGM0 = 1

L

RMS

1 pulse on FOUT2 =

60 * 230 * 3

3.83

= 10.8kWs

IL = 40ARMS,

PGM1 = 1 PGM0 = 0

1 pulse on FOUT2 =

40 * 230 * 3

2.55

= 10.8kWs

sames

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