Appendix C: Fg# 7894 - Hybrid Xt Push-Pull Vane - NRG Systems Hybrid XT Vane Product Manual

NRG Product Manual
Hybrid XT Vane
APPENDIX C: FG# 7894 – HYBRID XT PUSH-PULL VANE
Output Circuit Operation
The Model 7894 Push-Pull Hybrid XT vane was designed as a direct replacement for 1- or 2-Channel NPN-type IceFree3™
wind vanes. It provides two output signals, in push-pull format. These outputs can source current when on and sink
current when off for compatibility with a wide range of controller inputs, including those designed for existing NPN or
PNP sensors.
The two signals are Yaw Right / Yaw Left, denoted VL, and the Upwind / Downwind signal, denoted VR90.

White wire == VL (yaw right/left)

Yellow wire == VR90 (upwind/downwind)
XT Vane Dithering
Most yaw vanes, including many OEM sensors, are under-damped. They move left and right continuously as the blades
pass the nacelle and other turbulence affects the sensor. Some turbine control systems depend on this motion, called
dithering, to allow them to estimate the average wind direction while observing only one digital signal. The wind vane
output is off when the vane is left of center, and on when the vane is right of center. In these systems, the controller
compares how much time the sensor indicates left and how much time the sensor indicates right. When the turbine is
correctly pointed into the wind, the vane will indicate left and right equally, and the on / off ratio is 50%.
The Hybrid XT turbine control vane head maintains a stable output position that tracks the wind direction more
HybridXT_Vane_Manual
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support@nrgsystems.com | Page 25
7 February 2017
accurately and
varies much less
than under-
damped sensors.
For compatibility
with controllers
that are expecting a
dithered signal, the
electronics of the
Model 7894 Push-
Pull Hybrid XT Vane
creates a
compatible
dithered signal.
When the XT
senses the wind
direction is
correctly pointed
into the wind, the