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Do i need speed controller (brake) and charging controller for homemade wind turbine?
I made a wind turbine using car alternator(mico company 14v, 43A, rated rpm 1500) with 1:10 gearing and 10’ diameter wooden blade. The alternator does not produce power without connectind batteries and it has inbuilt voltage regulator (cut out system) which cut the charging battries when it reaches 14 volt. In this turbine i dont use any roter speed controller (brake) and electrical charge controller. In rated speed of alternator it work nice. But, if over wind speed time , is this volt regulator of this alternator wok? Or require brake and charging controller?
An alternator differs from a generator in that an alternator generates AC power rather than DC. With an automobile alternator, rectifiers and a voltaage regulator are integrated to change the AC power into DC power at a voltage level suitable for a topping charge of lead acid batteries (14.4 VDC).
When when rotor speeds change on a generator, the voltage changes but when rotor speed changes on an alternator the frequency of the AC sine waves changes so it's not necessary to regulate the rotational speed of an alternator provided that it is within the operating parameters of the alternator.
This is why alternators replaced generators in automobiles because the rpms differ widely from highway cruising speed to in town running around. A generator designed to charge at highways speeds would not charge when driven in town and a generator designed to charge in town would overcharge on the highways.
At higher speeds, the output of an automotive alternator would just have smaller ripples at a higher frequency but this is typically filtered out with a capacitor.
You do need something to protect the turbine from high speeds though, usually this is down by having the tail spring loaded such that it would fold flat to the propellers when released, a catch keeps it perpendicular to the propellers but when the wind speeds reach a certain level, the catch is released, a simple mechanical governor can do this or you could wire a solenoid up to a frequency to voltage converter with a zener diode on the base of the transistor controlling the power applied to the solenoid. This way, when the wind speeds reach a designated limit, the tail folds flat against the propeller turning the windmill such that the propeller is edge on to the wind, protecting it from high wind speeds. You have to reset it manually but this is the easiest way to brake the turbine.
Having a constant voltage of 14.4 VDC is suitable for a stage 2 topping or absorption charge and it's probably unnecessary to have the stage 1 constant current bulk charge but once the batteries are charged, they must go onto a float charge where the voltage is dropped to maybe 13 VDC and current limited to 1% of nominal current, nominal current is the current at which the battery rated capacity would be depleted in 20 hours i.e.: a 48 AH car battery would have a C of 48/20 or 2.4 amps and hence would float charge at 20 milliamps. A car alternator is basically sized to charge a battery with the nominal current C calculated as the capacity depleted within an hour hence the 43A rating; this is because it's assumed that you would want a battery mostly charged within an hour of driving time. This basically means that you need a charging controller to protect your batteries. You should never leave a lead acid battery on a topping/absorption charge for more than 48 hours, doing so will boil off hydrogen from the electrolyte. That's probably why the alternator's voltage regulator cuts off the charge at 14 VDC, hopefully it cuts back in when the battery voltage drops below 12.2 VDC
Note that if you use batteries that are unsealed, you can at least top off the cells with distilled water and check the specific gravity of the electrolyte in each cell. A battery is only as good as it's weakest cell so you may have to do an equalization charge once a year where you allow the batteries to be on the topping/absorption charge 10 to 15% longer than is warranted by the charge level hence boiling off hydrogen from the charged cell while allowing the weaker cells to catch up in their charge, you then fill the cells with low electrolyte levels back up.
Also, you don't want the battery room to get much hotter than say 80 F so keep it well ventilated. If it has a tin roof, you may wish to consider installing sprinklers on the outside of the roof to cool the room by evaporation but without increasing the humidity inside the room. I would probably use buried air intake pipes and a combination of a solar heat chimney and one of those wind vents to pull the air through the buried pipes cooling the air through the battery room and exhausting out the wind vent and or the heat chimney. That should help warm up the battery room during winter too since ground temperature is more or less constant year round below a certain depth.
The unfortunate thing about using car alternators is that it's for a 12 VDC system so if you can use the alternator from a bus which would be 24 VDC, you can reduce the current needed by half. I've often wondered if this would call for driving two bus alternators wired in series off one propeller to get 48 VDC since 48 VDC components rated at high currents are readily available from the telecom industry.
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