Overview

In rare cases, customers need the WattNode input impedances, sometimes to drive the WattNode from a potential transformer, sometimes for other reasons.

Vac Inputs

The WattNode Vac terminals (green connector) have an input impedance composed of two parts: the power supply load and the sense resistors.

The power supply load appears between the “N” and “ØA” terminals on models with “-3Y” in the model number, and appears between the “ØA” and “ØB” terminals on the models with “-3D” in the model number. The power supply is the primary load for these terminals.

The “N”, “ØA”, “ØB”, and “ØC” terminals all have sense resistors that are 2.4 mega-ohm.

Models “N” Input
Impedance
“ØA” Input
Impedance
“ØB” Input
Impedance
“ØC” Input
Impedance
Typical Power
Supply Burden
WNC-3Y-208-BN, -MB, FT10 3.4k 3.4k 2400k 2400k 1.9 VA @ 0.79 PF
WNC-3Y-400-BN, -MB, FT10 13k 13k 2400k 2400k 2.2 VA @ 0.73 PF
WNC-3Y-480-BN, -MB, FT10 22k 22k 2400k 2400k 2.1 VA @ 0.69 PF
WNC-3Y-600-BN, -MB, FT10 68k 68k 2400k 2400k 1.1 VA @ 0.76 PF
WNC-3D-240-BN, -MB, FT10 2400k 13k 13k 2400k 1.6 VA @ 0.70 PF
WNC-3D-400-BN, -MB, FT10 2400k 61k 61k 2400k 1.6 VA @ 0.67 PF
WNC-3D-480-BN, -MB, FT10 2400k 86k 86k 2400k 1.7 VA @ 0.70 PF
  • These are conservative estimates for the power supply impedances. The actual values should generally be higher, but are also complex, because the power supply load is non-linear.
  • The values for Pulse WattNodes are similar and generally a bit higher. Contact us if you need detailed values.

Current Transformer Inputs

The current transformer inputs all have a 23.0k input impedance between the white and black wires. Furthermore, the black terminals are referenced to the WattNode earth ground point through a resistance that varies from 20k to 60k.