Motorcycle Rectifier / Regulator

[Pedersenauto]

Hi,<p>I would like to rebuild my rectifier / regulator for the charging system for a old motorcycle, I have good stator that I check the voltage on the three winding, The voltage goes from 15 to 50 volts AC under each leg. under normal RPM's The problem is that the regulator is been destroyed from battery acid. I also had to chip away the epoxy from the circuit, but in the process of gutted the components from the heat sink. I only have been able to make out a few components 3 SCR's 25 amp 400 volts, 220 style The resisters 1k, possible 2.5 k and small pot 5 k two small transistors one is C2N5401 that seem to go to ground. the other transistor is burned up and three small diodes 1n403, one cap .1 , The stator is most likely has a magnet to induce the winding, my question is the design of the circuit and how the voltage is regulated to a charging voltage for the battery, when the rpms is changing the voltage and the magnet field is fixed value. Could someone draw a circuit I could use, also could I protect the circuit from possible damage to the winding if I have other electric problems.<p>Thanks Craig

[desterline]

Hi Craig,
What's the make / model / year of this bike?<p>I want down a similar path with a Suzuki GS750 I used to have. Turns out they had a *REALY* bad design for that one. But after much studying I found there were aftermarket replacement parts that were designed better.<p>Ultimately I sold the bike instead.<p>-Denny<p>[ October 12, 2003: Message edited by: desterline ]</p>

[Chris Smith]

I would start with over the counter Wrecking Yard parts. <p>Start with a new Rectifier from an electronics parts store, probably less than five bucks, and then use a car electronics regulator off a wreck, to do the regulation. They are cheap, self contained, and handle all the electronics nessary. You can hook up the regulation feed to a common transistor or even an old fashion relay to regulate the load.

[russlk]

Your alternator is apparently 3 phase (as is most alternators). Automotive types have a field winding for regulation and use 6 diodes for full wave rectification. The motorcycle must have used half wave rectification with scr regulation. I have never designed that kind of circuit, so can't help with a diagram.

[desterline]

Chris,
Since Craig hasn't told us which make / model yet, I can only generalize- but:<p>It has been my experience that automotive parts will -not- work. Standard automotive alternator design uses field coils to generate the magnetic field. They then regulate the output of the alternator by regulating the current to the field coils.<p>Most motorcycles use a permanent magnet rotor and a shunt regulator. A very different and incompatible method.
-Denny

[Chris Smith]

I’ve had bikes since the 70s all the way to the 90s. <p>The old type motor cycle [70s] doesn’t need a regulator because it used a fixed out put current and then consumed that exact output. When the lights were switched on, another coil was brought into play, and the head lights also connsumed that current. Brake lights, taped out of the battery which was under a constant current charge, but small. <p>The British just shunted excess current/voltage to ground via a Huge Zener diode. <p>The Newer types use a field winding of variable control, and Car type regulators, the Solid state types used in Italian, German or French cars [Bosch, Marelli, or Bendix] can work on them via a direct connect, or a set of points as in a relay.

[russlk]

I did some research and offer the schematic that you will find at this URL: http://www.poptronics.com/forums/electr ... index.html
Hmmm, I just remembered that the 5K resistor should be 6.8K. I will try to edit the schematic.

[cato]

This page:<p>http://www.electrexusa.com/electrex_tech_charging.html<p>Has a good generic schematic for a motorcycle rectifier/regulator as well as a good explanation as to how it works. In a nut shell, there is a three phase bridge rectifier which does all the work until the engine speed is such that the voltage out of the alternator exceed a threshold. They say the threshold is 14.4 volts. At that point some sort of switch shunts current to ground to keep the voltage from exceeding the threshold. Apparently, in your case, and in the case of my Suzuki Intruder, the swiches are SCRs.

[Pedersenauto]

Thanks To all that help on the Problem regulator,
The bike is a 85 Volcan VIN # JKAVN6A1XFA000327
700 cc V-twin. It doesn't work like a car regulator That's what I work on all the time, It has fixed magnet for the field. and the load is regulated from the stator winding, as cato has posted a link to. Any coments as to the design that was posted from Russ Kincaid. Thanks I will try building the circuit. what watt parts do think will do the trick.
Craig

[cato]

Pedersenauto -
Your original post combined with the schematic I sent you to would seem to be just about all you need. You know what diodes to use and you know what SCRs to use. All you need is some sort of comparator circuit to control the SCR's. Look up their switching characteristics and go from there. I would suggest a set of simple voltage dividers to do that. However, at this hour of the morning, and without the schematic infront of me, I'm not sure that a voltage divider wouldn't cause a constant drain on the battery (even when the ignition is off), therefore I'm not recommending that. Thats probably what the two transistors were doing, switching some sort of voltage sensing circuit on when the supply voltage indicated that the alternator was running.

[Joseph]

I once had a Harley street/trail bike for which I dedided that I would quit buying batteries. So, I ran the output of the rectifier through a high current linear voltage regulator into a big capacitor.

[Edd]

WHATS THAT.......Exactly... HOW many Farads did you you say ?..
73's de Edd

[Joseph]

I used something like a 10 or 20,000 uF computer grade capacitor. If it is too large, it will take too long to charge up when the starter is kicked. If the voltage can come up quickly, the spark will be produced sooner. But maybe the ignition on that bike used a separate magneto which could explain why it worked so well.<p>[ October 21, 2003: Message edited by: Joseph Meisenhelder ]</p>