Motorcycle Rectifier/Regulator for 12V 500W Wind Turbine

[plasmahunt3r]

I have a new regulator for my 12V 500W wind turbine. I spent $27 off Ebay for a new 2007 Harley Softail Voltage Rectifier/Regulator. I picked the 2007 because the wires are longer. The 2008+ Rectifier/Regulators have very short wires. I cut off the plugs and soldered on ring Terminals.  The regulators come encapsulated inside a heat sink and are waterproof. 

The Harley's put out 3 phase AC up to 38 Amps. The Voltage Rectifier/Regulator is a shunt type regulator that kicks in at 14.5V.

The way this works, is to simply rectify the voltage until the voltage reaches 14.5V, then shunts the excess voltage to ground. This shunt occurs only on the positive wave of the AC cycle.  I tested the wind gen with a power drill and socket spinning the turbine. When it reached 14.5V, the torque increased on the drill and slowed it down. In this way, that shorting to ground acts as a brake and slows down the wind turbine to keep it from over spinning. Shorting to ground is what a brake switch does, except this is temporary, until the voltage drops below 14.5V. 

This results in a self regulating and self braking turbine.

The Harley Rectifier/Regulator should work with higher wattage and higher voltage turbines as long as you are charging 12V batteries. It all cases, the voltage is clipped at 14.5v, then the torque on the turbine is increased, thus slowing turbine.  A Harley can power through the torque because it has an engine.  The wind gen can't power through the torque, so it brakes.

[Adriaan Kragten]

I have some comments on this story.
 
First, a voltage of 14.5 V is very high to protect a 12 V battery from being over charged. Normally the maximum charging voltage is limited up to 13.8 V, so to 2.3 V per cell. I think that the battery of a Harley will be gone very fast if this high maximum charging voltage is allowed. The voltage regulator of a Harley may make contact with the earth at a high frequency but this is done such that the average charging voltage is maintained at 14.5 V. Making real short-circuit, even for a very short time, would be very bad for the battery.

Second, for the windmill it doesn't matter if the charging voltage is limited by a big battery or by a voltage controller. For a constant voltage of 14.5 V, the generator will have a certain Q-n curve which lies only a very little to the right side of the Q-n curve for 13.8 V but very much to the right side of the Q-n curve for short-circuit. So if you really want to slow down the rotor, you have to make real short-circuit. The highest short-circuit is gained for short-circuit in delta (or for short-circuit in star if the star point is short-circuited too). Measured generator curves for different constant voltages and for short-circuit in star and in delta can be found in my free public report KD 78 (see website: www.kdwindturbines.nl).

Slowing down the rotor by short-circuiting of the generator winding can never replace a safety system which limits the generated torque and the thrust because there is always a wind speed for which the Q-n curve of the rotor will lie higher than the Q-n curve of the generator for short-circuit. The wind speed for which the Q-n curve of the rotor will lie higher than the Q-n of the generator for 14.5 V will be a lot lower than the wind speed for which the Q-n curve of the rotor will lie higher than the Q-n curve of the generator for short-circuit. So maintaining the voltage at 14.5 V will give problems of over speeding much sooner than for short-circuit. However, over speeding during short-circuit will burn the generator winding sooner as all the generated heat has to be dissipated in the generator winding.
 

[DamonHD]

I had an 'emergency' SCR brake on my toy turbine, *upstream of a diode leading to the battery* (so the battery itself was never shorted), and the mechanical crunch from it firing indicated to me that using it much was not kind.  (On very windy days I tied the turbine up instead.)

http://www.earth.org.uk/wind-power-pilot-autumn-2007-MotorWind.html#crowbar

Rgds

Damon

[plasmahunt3r]

Thank you Adriaan Kragten for your comments.  I put a meter to my Harley and it puts out 14.4V with the motor running.  My plugin AC battery chargers also put out 14.5 volts.  My Harley battery last about 2 years, so the high voltage may be a problem.  Of course, there are also loads on the battery while the motor is running (lights, ignition coil, etc).  The short is based on SCR's, so it shorts to ground, only on the positive half wave, of the AC side, when the voltage limit is tripped.  This short is on the AC side to ground and not on the battery to ground. 

For the wind gen, I am using AGM batteries and the battery manufacturer recommended a charging voltage of 13.8v for standby batteries.  I am using them on a sailboat, so the batteries will be standby until I leave the dock, so 13.8v would be better.   I tested today adding a diode between the Rectifier/Regulator and the battery; and the torque hit at 13.9v.  That braking does slow down the turbine to keep it from over spinning.  I mounted the turbine on my truck and ran it up to 50 MPH, and the wind wasn't enough to overcome the braking effect of the positive half wave AC to ground.

A Harley has a 96 cubic inch engine to overcome the shorting to ground and produce max amps.  The AC stators don't burn out on motorcycles using this method, so I don't think there will be any long term damage to the Wind Gen.  But, it's my Wind Gen to play with.

[plasmahunt3r]

Thank you DamonHD for your article.  I am familiar with that method and they are using a single SCR as a brake on the DC side.  Once tripped, the SCR will stay on until the voltage drops to zero. That extra diode is there to prevent the battery draining through the SCR.  It works, but the SCR has to handle all the current.

The Motorcycle Rectifier/Regulators are using 3 SCR's on the AC side to ground (one for each AC phase).  Since there are 3 SCR's, each handles 1/3 of the total current.  They will reset at zero crossing independently for each phase and only turn back on if the voltage trigger is still set.

[joestue]

the VA's demanded from the alternator from an scr regulator are pretty much exponentially bad for wind turbine alternators.

basically the amps go up with windspeed squared, volts proportional to winspeed.

but when you use an scr rectifier to regulate the voltage down, amps into the battery go up with winspeed cubed. problem is.. the scr rectifier only drops the rms voltage, not the amps. amps going into the battery = amps coming out of the alternator.

if however you use a diode rectifier followed by a buck converter, amps from the turbine follow winspeed squared as the volts rise. amps into the battery follow winspeed cubed, and the buck converter handles the conservation of power, turning volts and amps into lower volts and higher amps. the scr regulator can't do that.

A Harley has a 96 cubic inch engine to overcome the shorting to ground and produce max amps.  The AC stators don't burn out on motorcycles using this method, so I don't think there will be any long term damage to the Wind Gen.  But, it's my Wind Gen to play with.

Whether or not that works also depends on the alternator. the harley is likely a high frequency alternator that is impedance limited using ferrite magnets.

[DanG]

And the reminder that highest allowed voltage out will be dropped across every splice, cable, lugs and fuse, a 5% drop yields 13.8V...

[OperaHouse]

I picked up a wind regulator, don't know why. It had braking I thought was interesting.  Besides having a FET to switch in the brake, the load resistor was made up of 24 (two banks of 12 in series) thermal resistors.  These are the kind you see in power supplies to limit initial charge current and are about 20 ohms cold and 1 ohm hot.  So if there is a momentary gust the braking is light.  Sustained high wind speeds and the resistor bank would turn into almost a dead short.  I thought that was novel.

[DamonHD]

Those thermal resistors in series with the SCR in the circuit I put together might work quite well!  I might then still have an 'even more emergency' plain SCR crowbar if the gentle one wasn't doing the job...

Rgds

Damon

[plasmahunt3r]

The Black Heat Sink Device is the Harley Softail Regulator.  I feed it into a 2 Farad capacitor which is parallel with the battery.  The cap is to help with surges, like when the refrigerator kicks in.