braking dc motor.

[snake21]

hi friends,yesterday i tried something,i dont know if you use it already or its not good prtice but i am just sharing comments and advice re most welcome.

i have an ametek 38vdc which i am using to charge a 12v battery.yeterday night,the wind was blowing at about 30mph and gusts of bout 50-60mph.i did ll the blades ballancing and the turbine was spinning like mad.i was scared if ever it self distruct at night.then i just got an idea of applying some brake to it.what i did,i just connect 2 wires,i from negative battery and the other to the positive turbine,just before it pass through the diode,then i have connected a car 12v 150w headlight to it.the bulb light on and starts fading,i then went to take a look at the turbine,it was spinning at about 100rpm instead of very high rpm.

i dont know if it is good pratice,but it helped the whole windy night,and i slept peacefully

[Flux]

What you did was reasonable. You increased the load to the point where it stalled the blades. Once it stalled, the lamp resistance dropped quite low and held it stalled.

At least you didn't try a direct short as is done with the brake switch on the alternators. Dc motors are rather limited in overload capability on the commutator and brushes and the Amteks are allready fairly well pushed on wind duty. A direct short would almost certainly do damage to the brushes and commutator surface.

As long as you use a resistance or lamps to limit the maximum current you will probably be ok.

Flux

[97fishmt]

Nicely done, most folks try to test out their turbines with a car head light
and the turbine just peters out and they get discouraged that it wont light
up the light.

It doesn't work that way.  The battery is there to let the turbine come up
to charge voltage or cut in voltage and a dump load, or in you case a head
light is for over voltage protection.

The wind turbine wont power the head light directly, it has to go though
a battery to let it spin up.  I've always found enough load to stall the turbine
if needed.  It can be a hair raising experience  to try a new turbine and no
idea how it will behave.

Sounds like you have some good wind?
If so it might be time to add a furling tail and have it be automatic and not worry.

[snake21]

hi,thanks for your comment,now i am sure that what i did was ok.

there is a lot of wind at my place but the problem is not the motor output but the blades.i rewound the ametek with some more turns and some thicker wire.i think that i would be able tohole up to 15amps at 12v now.the maximumi saw in high winds was only 6amps at 12v.it can produce more but the pvc blades i am using will not be able to hold high rpm which i need to produce more power.just to prevent the blades from shattering that i connect a load directly to it.