Author Topic: 3 phase Shunt Regulator  (Read 5061 times)

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plasmahunt3r

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3 phase Shunt Regulator
« on: January 19, 2016, 10:32:07 PM »
I wanted to share my 3 phase Shunt Regulator with you.  While I have a 12v system, this circuit can be easily modified for 24v and 48v systems by changing the Zener and appropriate values for capacitors.

The circuit works by first converting AC into DC via the 3 Phase Full Wave Bridge Rectifier to charge your batteries. When the voltage limit is reached (set by Zener plus .6v for PNP Transistor), the SCR's are turned on and dumps the excess voltage to ground, via the dual 300W Dump Resistors.
 
The dump occurs for each of the 3 AC phases on the positive half cycle and resets for each wave (SCR's turn off at zero voltage or negative voltage). Each positive AC phase dumps excess voltage to DC ground.
 
The Dump Resistors (dual parallel 300w = 600W) provides a load for the turbine so it is not a dead short. This dump is only for the Turbine and not a drain on the battery. This load also slows down the Turbine (Braking).
 
The trigger is the PNP transistor.  What happens, is when the Zener breakdown voltage is reached, The PNP gets a negative pulse on the base to turn it on. That allows the positive rail voltage to pass from the PNP emitter to the collector, which turns on the SCR's. I am using a PNP because I need positive voltage to the SCR gates to turn them on.
 

margusten

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Re: 3 phase Shunt Regulator
« Reply #1 on: January 21, 2016, 01:35:57 AM »
It is good idea.
SCR's (triax) laying around here and I didn't know where to use these.
SCR's usable only at AC.
I have this model up and running:
http://www.ebay.com/itm/48V-1-5-KW-Modell-i-1500-WINDGENERATOR-von-iSTA-BREEZE-WINDKRAFTANLAGE-2-10m-/381525698035?hash=item58d4b425f3:g:pgIAAOSwBLlVZhqa
Going to try Your circuit at summer.

plasmahunt3r

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Re: 3 phase Shunt Regulator
« Reply #2 on: January 21, 2016, 08:30:55 AM »
Margusten.  It will not work with Triac's (Triacs conduct in both directions).  You need to use a standard SCR.  The purpose of the SCR is to conduct only in one direction.  I am using 2N6509 (800v 25A) SCR's.  The SCR's oscillate ON/OFF (On during the positive Half Cycle on the AC side and dumps to the DC negative through Dump Load Resistors).  You can buy 2N6509 cheep on Ebay.

Also, keep in mind, that in 3 Phase AC, each phase is 1/3 of your Turbine total power output.  For instance, if your Turbine puts out max 21 Amps, the each phase of your AC is 1/3, or 7 Amps.  In that case, the three SCR's at 25A are overkill for my system.  I always exceed the level reguired for my components.

OperaHouse

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Re: 3 phase Shunt Regulator
« Reply #3 on: January 21, 2016, 11:12:53 AM »
I have been missing GHURD.   Diversion power ought to be used somewhere.  AC side solutions make that more difficult with three separate loads.  Favor something like leterblow's  Wind Powered FET Destroyer which is more digital..

plasmahunt3r

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Re: 3 phase Shunt Regulator
« Reply #4 on: January 21, 2016, 02:47:49 PM »
Operahouse.  I looked at DC Side Diversion Load options and Leterblow's Fet circuits.  I am not knocking those approaches.  There are 14 ways to skin a cat.  I wanted something that ran unattended, partially braked the Turbine in overspeed conditions, automatically dumped excess voltage while capping charging voltage, highly reliable, and required few parts.  I like the Keep It Simple approach.

SCR's run cooler than MOSFETS, and in my circuit, they cycle ON/OFF on positive AC cycles, and only when the voltage exceeds the Zener/PNP trigger voltage.  Since wind speed is variable, the SCR's only get invoked to protect the Turbine and  Batteries when the voltage limit is reached.

The dual 300W Dump Load Resistors are providing the load for the Turbine when the SCR's are triggered, and it that respect, they become similar to the standard diversion load found in DC side circuits.

I think my circuit is simpler, more reliable, and meets expectations.

plasmahunt3r

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Re: 3 phase Shunt Regulator
« Reply #5 on: January 21, 2016, 05:41:22 PM »
Here is a pic of the board layout:


plasmahunt3r

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Re: 3 phase Shunt Regulator
« Reply #6 on: November 13, 2016, 07:33:36 AM »
I have an update to this circuit.  The voltage limit is set by Zener plus .6v for PNP Transistor. 

I have been using a 14V Zener (which was actually 13.8v plus the .6V for the PNP transistor resulting in 14.4V charging current.

Since these batteries may be left unattended for a long period, I should use Float Voltage.  For AGM battries, this should be between 13.5V to 13.8V (13.6V is optimum float voltage for AGM Batteries).  The 14.4V may overcharge the batteries in the long term.  For this reason, I am swapping out the 14V zener for a 13V zener.

OperaHouse

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Re: 3 phase Shunt Regulator
« Reply #7 on: November 13, 2016, 08:51:02 AM »
You never quite get what you want from a zener.  That is why I like to use the LM431 for the reference.  Then you can just put a little pot on it and adjust what you want, like a setting for away or equalize.  Are those the 300W resistors from China.  I was just looking at 3 ohm ones for a dump load on a solar panel tester.  What did you think of the quality?
« Last Edit: November 13, 2016, 08:56:21 AM by OperaHouse »

plasmahunt3r

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Re: 3 phase Shunt Regulator
« Reply #8 on: November 13, 2016, 07:05:13 PM »
I don't know where the resistors are made.  I bought them on Ebay using the search "Dump Load Resistor".

The circuit is fine in it's simplicity.  It is modeled after the old Triumph Motorcycle Voltage Regulators.  The British bikes like BSA and Triumph used "Shunt Regulators" while Harley uses "Series Regulators".

If I redesign and rebuild the circuit later, I may use dual voltage references handled by a switch.  One voltage for Fast Charge and one for Float.  It gets too complicated if I use a microprocessor to sense and automatically switch from Fast charge to Float.

My needs are a little different than most.  I am using the wind generator exclusively for refrigeration on a sailboat.  The boat's refrigerator, when docked, is running on AC and the batteries are being charged by the wind generator and sitting ready.

OperaHouse

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Re: 3 phase Shunt Regulator
« Reply #9 on: November 14, 2016, 02:37:43 PM »
Simple is great, but finding the right zener can be difficult.  Even a 13V 5% zener can be off more
than half a volt each way.  A zeners voltage can always be boosted up about a quarter volt with a
Schottky diode or .6V with a silicon diode using their forward voltage. The band has to be opposite
of the zener.  The LM431 can be found in old PC power supplies and wall warts.  It will be connected
to an opto isolator on the low voltage side. Anything that has 431 on it is likely one. In quantity
they are less than a nickle each.  I can mail some if you want to try them. I also have a crap
of 18V zeners. I wouldn't use a no name one at over 28V. You can still put any zener in series if
higher voltages are needed.  If R is tied to C then it becomes a fixed voltage zener. If gotten cheap
five could be placed in series for 12.5V

The following circuit uses a single 431, 68K, 15K resistor and a 4.7K pot.  It has an adjustment
range from 11.0V to 14.2V.  That 11V setting could be used when you want to batten down the hatches and heat the cabin.  The higher end to equalize the batteries.  It looks a little bit of a mess
because I have thousands of these 1.2K resistors and the 10K were handy.  A simple way to figure
out the resistance values is this.  The lower resistance represents 2.5V.  Multiply that for every
additional 2.5V.  The current through the 431 is minimal, but there will always be current through
the voltage divider of 88K total resistance. 

Mary B

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Re: 3 phase Shunt Regulator
« Reply #10 on: November 14, 2016, 06:23:19 PM »
When using a 3 terminal voltage regulator you MUST use electrolytic capacitors on the input and output to remove the noise they generate! This it the typical bypass arrangement...


OperaHouse

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Re: 3 phase Shunt Regulator
« Reply #11 on: November 15, 2016, 07:18:59 AM »
He's got a cap close by.  A431 is very stable unlike 3 terminal regulators.  While it is  on even a zener to get rid of noise, a cap across this would likely introduce a whole can of worms.  I always invite people to experiment, that is how you learn.

plasmahunt3r

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Re: 3 phase Shunt Regulator
« Reply #12 on: November 21, 2016, 10:35:44 PM »
Hey Operahouse.  Thanks for your TL431 information.  I have been looking into it and I may have a use for it.

Currently, I am using the Zener as a trigger for the PNP transistor, which in turns passes Positive Voltage to the SCR gates for each phase, and the three SCR's shunt the excess voltage through the Dump Load Resistors.

If I use the TL431 as a comparator, instead of a Zener replacement, then I think I could eliminate the PNP transistor and use the TL431 to pass a positive voltage to the SCR gates when R1/R2 becomes greater than Vref(2.5v).

I will do some experimenting.