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.