MCP39F511A datasheet(27/68 Pages) MICROCHIP

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DS20006044A-page 27

MCP39F511A

5.9

Power Factor (PF)

Power factor is calculated by the ratio of P to S or active

power divided by apparent power.

EQUATION 5-5:

POWER FACTOR

The power factor reading is stored in a signed 16-bit

complement register with the MSb representing the

polarity of the power factor. A positive power factor

means Active power is being imported, a negative

power factor represents export active power. The sign

of the reactive power component is used to tell if the

current is lagging the voltage, with a positive sign

meaning an inductive load and a negative sign

meaning capacitive. Each LSb is then equivalent to a

weight of 2-15. A maximum register value of 0x7FFF

corresponds to a power factor of 1. The minimum

of -1.

5.10

Reactive Power (Q)

In the MCP39F511A device, reactive power is calcu-

lated using a 90 degree phase shift in the voltage chan-

nel. The same accumulation principles apply as with

active power where ACCU acts as the accumulator.

Any light load or residual power can be removed by

using the Offset Reactive Power register. Gain is cor-

rected by the Gain Reactive Power register. The final

output is an unsigned 32-bit value located in the

Reactive Power register.

Please note that although this register is unsigned, the

direction of the power can be determined by the

Reactive Power Sign bit in the system Status register.

FIGURE 5-5:

Reactive Power Calculation Signal Flow.

---



OffsetReactivePower:s16

ACCU1

HPF

ReactivePower:u32

HPF (+90deg.)

GainReactivePower:u16

Range1,2:b32

2N-1

÷ 2N



÷2RANGE

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