Residential Wind by Way of Illustration - Wind Power for the World: The Rise of Modern Wind Energy - page 584

alternator winding. Its resistance is not that high—power is limited.
When the controller stops the turbine, it creates losses in the
winding too, but it also directs power to the battery and/or dump
load—the deceleration becomes faster and more reliable. Eventually
the controller short-circuits the turbine through transistors on its
board (shorting is a part of boosting as described above; transistors
are already there, in combination with controller intelligence
using them for stopping is only logical).

26.8 Blown Fuse Mode

If the battery is selected properly and it is in a good shape, its
internal impedance is low, its voltage is comparatively stable. The
battery is connected to the output of controller; it uses it to limit
its input voltage coming from the turbine. But what if the battery
fuse is blown or battery is accidentally disconnected (not all
turbine owners are electricians, sometimes they don't realise
the full consequences of their actions)? The controller can short-
circuit the turbine, that is, make the voltage zero. Problem with
that is the need of power for controller to operate. With battery
disconnected for whatever reason and turbine shorted, the
controller can use the energy stored in filter capacitors on its
board for short time, but they have to be recharged at least from
time to time for continuous operation. The mode is realised the
following way. As soon as the controller detects that the battery is
lost, it shorts the turbine. At the same time it senses the voltage of
filter capacitors. When it drops below preset level, the controller
“releases” the turbine for a split second to give capacitors a pulse
of current, checks the voltage again and repeats that until filter caps
are recharged to upper preset level. Then the cycle is repeated,
starting with shorting. Thanks to the automatic blown-fuse mode
controller remains operational and protects itself from excessive
voltage of unloaded turbine.

26.9 Equalising Mode

To maintain some battery types healthy they have to be equalised
approximately once a month. During that mode the controller
creates higher than usually voltage on the battery during several