MCP39F511 datasheet(26/62 Pages) MICROCHIP

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MCP39F511

DS20005393B-page 26

 2015 Microchip Technology Inc.

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, 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 register value of

0x8000 corresponds to a power factor of -1.

5.10

Reactive Power (Q)

In the MCP39F511, 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 the 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 in the system status register.

FIGURE 5-5:

Reactive Power Calculation Signal Flow.

---



OffsetReactivePower:s32

ACCU1

HPF

ReactivePower:u32

HPF (+90deg.)

GainReactivePower:u16

Range1,2:b32

2N-1

÷ 2N



÷2RANGE

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