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Last Updated: September 20, 2013

3 Phase Voltage regulator (SERIES TYPE)


The circuit is straight forward, It is not a shunt regulator, but a SERIES type of voltage regulator. D1 to D6 comprises the RECTIFIER diode which converts the AC generated by the 3 phase stator, Q1, Q2 and Q3 as the switch that controls the flow of voltage and current to charge the battery, Q1 and Q2 must be heatsink, since this type of regulator is in series mode, and no shunting will happen on all the windings, thus LOAD is particulary important on this kind of regulator.
IC2 inverting input has a two resistor in a differential way thus R4 and R5 is very critical on this design so the value must be at least 2% tolerance. When the IC2 input sense a high voltage, it switches ON Q4 and immediately allow it to control those power transistor flow via Q3, the circuit in RED is like a faucet that controls the flow of water. The circuit in GREEN are the voltage sense circuitry, and The Blue box is the source voltages with the rectifying diodes.

The switch of course is your ignition key, R4 and R5 must be wirewound type, since when this is active, they are in parallel with the battery, and engine must be running to avoid battery discharge.

Remember that this circuit when no load will produce a high voltage, Of course this is a series type. highly different with the way SHUNT regulators.

To make this work on a single phase, just omit the other two winding and use on one. A-B or B-C or A-C.


Resistor 1/4 watts

R1-----1.5k ohm
R2-----1k ohm
R3-----200k ohm
R4-----*3.9k see notes
R5-----*18k see notes
R6------2k ohm
R7------200 ohms


C1-----100uf/50 volts
C2-----47uf/50 volts

D1-D6-----1n5404 (3A 400v rectifier diode)
DW1-------16 volts zener diode 500mw




IC2-----uA741 or LM741

notes: * will determine the the on and off time of the op-amp that will control the base of Q3 to where it switches the power transistor Q1-Q2 for the right voltage output to the battery.

3DD15 look like this

3DG12 look like this


Abu-Hafss said...


Can 3DD15 be replaced with TIP150 (TO220 package) and 3DG12 with 2N4401 (TO92 package) ?

By the way, which type of regulator is more efficient, SERIES type or SHUNT type?

The diodes used for rectification are 3A rated. Are they enough? For the shunt type regulator, I have seen (on net) somebody using 12A bridge rectifiers and another using 25A diodes.

Nathaniel Berdan said...

you can replace those power transistor to any of your type as long as your intended application can handle the needed power..for example you need 150w, then definitely the rated power handling of the (3DD15) must be above 150w,

Series is more efficient because it does not constrain the stator winding.

The rectifier diode rating will depend again on the stator power output.

Abu-Hafss said...

The schematic shows that the battery will be charged thru the ignition switch!

R4 and R5 forms a potential divider to give input to pin #3 of op-amp 741. If we increase their values to Mega ohms, we can get same voltage at pin #3 but with lesser current thru those resistors.

And how about replacing those mighty 3DD15s with a TO-220 mosfet IRF740A.or some other suitable device? Actually I want to reduce the size of the circuit so that it can accommodate within the same housing as that for the shunt type regulator.

Nathaniel Berdan said...

we all know hoe bipolar transistor and mosfet transistor works, they are different when it comes to switching, if you can make the FET work in that system, i'll be very glad to see it..I do not have time to experiment with it. You can make it smaller in size when it comes to PCB by using SMD, goodluck and feel free to post it here., afterwards fro others.

Abu-Hafss said...

By the way, how do we find out the maximum power generated by the stator of a particular bike or a three-wheeler?

Nathaniel Berdan said...

just put more load on the system, if the the voltage start to drop, then you have reached the maximum output of your stator. This scenario is only applicable at a certain RPM to where the stator will produce the maximum output..(for example my motorcycle stator that works hard at 5ooo rpm)..

Unknown said...

what is the output of this regulator when connected to the battery during initial charging? Tia.

Unknown said...

ERRATA: BTW, is the R7 in your schematic 2000 ohms? or same with the parts list = 200 ohms. TIA.

Unknown said...

May I know the available easy to find equivalent transistor number for 3dg12?

Abu-Hafss said...

You may use 2N2222 in place of 3DG12.

Abu-Hafss said...

It is 200 Ohms.

Abu-Hafss said...

The term "Voltage Regulator" indicates the output voltage is dependent on something. The circuit is designed to sense the battery condition and supply regulated voltage/current accordingly. Normally, for a 12V battery the charging voltage is 14.4V

Sonja Dević said...

Has anyone achieved to made this?
what are the possible proportions of the heat sink?

Stelios Stavroy said...
This comment has been removed by the author.