MCP3909RD-3PH3 Microchip Technology, MCP3909RD-3PH3 Datasheet - Page 96

• Manufacturer Part Number: MCP3909RD-3PH3
• Description: REF DESIGN FOR MCP3909 W/18F2520
• Manufacturer: Microchip Technology

Specifications of MCP3909RD-3PH3

• Main Purpose: Power Management, Energy/Power Meter
• Utilized Ic / Part: MCP3909, PIC18F2520, PIC18F4550
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

MCP3909 / dsPIC33F 3-Phase Energy Meter Reference Design
C.14 RELATIONSHIP BETWEEN ERROR AND CURRENT
DS51723A-page 96
For a given load and frequency, the absolute ratio error and angle error increase when
the primary current decreases from the rated value for un-compensated current trans-
former. The reason is that with the decrease of the secondary current, the magnetic
permeability µ of the iron core varies non-linearly, resulting in less reduction in the field
ampere turns.
Figure C-8 is a typical curve for load current and the phase lag of a CT. Generally,
phase lag of the output signal is great when the load current is small, and also
increases at a fast rate.
FIGURE C-8:
Current Load Versus CT Phase Lag.
Phase Lag
Current Load
© 2009 Microchip Technology Inc.