Load shedder/shunt question

[domwild]

Hi,

Have seen two or three different systems of load shedding for wind mills:

Phil Graecen's/Hugh Piggott's shedder uses the load in parallel with the battery, so the mill will charge the battery (? already full) and the load in high winds. Is it a case here of a larger resistance, i.e., the load, ensuring that the battery does not get overcharged any further. In other words, two resistances in parallel.

Another system disconnects the battery altogether and switches the load in. Is there a danger here that in a period of high winds (hope, hope!), the battery does not even get float-charged any more??

A third system for bigger mills switches the load in at the AC side and leaves the batteries connected, at least a simplified circuit diagram seems to imply that.

Any comments on the first two methods?

[Nando]

The different techniques to load the wind mills depend on the designer to reduce the designer's mental load or the pocket expenses or even the technical capabilities.

The best ballast is the one that loads the wind mill to a level that does not allow battery charging and the battery is isolated from the ballast and the wind mill.

Saying all that mouth full, a DIODE can be the disconnect "apparatus" and the ballast brings the wind mill generator voltage below the battery voltage for the diode to do the disconnection.

A good controller protects the battery and at the same time keeps the battery in float mode, even if the external load is applied to the battery.

This represent 2 & 3 items in your message.

Nando

[solarphil]

A wingen manufactured here in Aus. called the SOMA, used to connect the dump load in parallel to the battery when its controller decided that the batteries were full.  

They have only recently changed their approach.  

When the batteries are full the generator output is now directed to a seperate dump load instead of connecting the dumpload to the battery.

I believe that this latter approach is more bulletproof because if the battery bank should open circuit, the windgen will now default to the dump load instead of free wheeling.

Even the humble Chinese built 200watt windgen defaults to the dump load if the battery is disconnected!!

Phil

Geelong

[Slingshot]

If you are talking about a "dump" load, as in a shunt controller, then it is generally a very bad idea to place it in parallel with the battery.  It is a good idea to switch this load onto the generator side of the rectifier.  

In the case of a setup like my Ametek PM-motor generators, there is always a series diode to prevent battery drain back to the motor.  Placing the diversion load on the motor side of the diode ensures that you will not "dump load" the battery (and drain it) if the controller circuit malfunctions.

For a 3-phase alternator, the idea is the same, but you would implement an AC dump load before the 3-phase rectifier ... same result, the battery is protected from discharge through the diversion load.

[ghurd]

"very bad idea to place it in parallel with the battery",  "implement an AC dump load before the 3-phase rectifier",  "diversion load on the motor side of the diode"

I think I have to disagree.

Please explain the line of thought.

G-

[domwild]

Thanks for all the answers so far.

Regards,