MCP39F521 datasheet(25/52 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS20005442A-page 25

MCP39F521

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. Positive means inductive

load, negative means capacitive load. 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 register value of 0x8000 corresponds to

a power factor of -1.

5.10

Reactive Power (Q)

In the MCP39F521, Reactive Power is calculated using

a 90 degree phase shift in the voltage channel. The

same accumulation principles apply as with active

power where ACCU acts as an accumulator. Any light

load or residual power can be removed by using the

Offset Reactive Power register. Gain is corrected by

the Gain Reactive Power register. The final output is an

unsigned 32-bit value located in the Reactive Power

Please note that although this register is unsigned, the

direction of the power can be determined by the

Reactive Power Sign bit (SIGN_PR) in the System

Status register (Register 6-1).

FIGURE 5-5:

Reactive Power Calculation Signal Flow.

---



OffsetReactivePower:s32

ACCU1

HPF

ReactivePower:u32

HPF (+90deg.)

GainReactivePower:u16

Range:b32

2N-1

÷ 2N



÷2RANGE

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