Help with Shunt Regulator

[VinceB]

Hello,

I am starting to build a wind generator using Hugh's Axial Plans. The problem I have is the voltage regulator. I didn't want to use the one included in his plans because the relays will probably fail often and need to be replaced. So I found a shunt regulator at homepower.com:

http://www.homepower.com/files/shuntregulator18.pdf

I have a few questions about it

1. First, about the dump load. I tried searching for 1 ohm resistors on DigiKey but they are all over $20 for one. I find that expensive for wasted power! I know I could put a heating device, but the genny will be used in the summer only, so it's not necessary. Any advice on what could be used for cheap? I am thinking about a fan, but I am not sure it would pull enough power to regulate the battery voltage.
   
2. Second, Hugh's design is rated around 500W. I was thinking about putting a load in the shunt regulator that would pull about 500W from the batteries, so that in case the genny is running fast, the batteries don't overcharge. BUT, I was wondering, if I do as mentionned, and the genny is only running slow, the load will suck more than what the genny offers, so the remaining power will be coming from the batteries. Hence, their voltage will drop quickly. So the regulator will shut. And then, the voltage will rise back because of the genny, so the regulator will start again. I am wondering if there could be problems because of this ON-OFF-ON-OFF situation.. just to maintain the batttery voltage constant.
   
   

Thank you for your help

Vincent

[TomW]

Vincent;

Off the top of my head I suggest heating water, we all use hot water. Build in some  hysteresis  for the dump load. By that I mean it will only draw down your batteries a certain amount like starts dumping at 14.4 V and stops at 13.4 V or something.

Cheers.

TomW

[windstuffnow]

  You can make your own "heater" using Nichrome wire ( safety wire ).  Coil it in open air or wrap it around a ceramic rod.  Quite cheap and it works very well.  I usually take my ohm meter and slide the probe down until I get the resistance I need and cut, then make it fit my application.

   I used a pair of the shunts from HP for many years and they didn't seem to care about the cycling... worked very well.

.

[drdongle]

Heat coils from an old air conditioner/heat pump are available free from junked units. I found one recently that had 3 12 Ohm sections rated at 14.4 KW.

[VinceB]

Where can I get Nichrome wire ?

What gauge should I use ? I am thinking about 0.5 ohm of resistance.

It will not be damaged with 30 Amp running through it ?

Thanks

Vincent

[drdongle]

You can get Nicrome wire from old heaters..............

[deloiter]

Keep in mind that Chris Greacen's shunt regulator is only rated at 15 amps.

[inode buddha]

Old clothes dryer coils, toaster oven elements, etc. would work if you're on a budget, I bet. Electric stove elements, electric water heaters, etc. I've measured a few things like that in the past, and  I don't see why it wouldn't work.

[Nando]

The SHUNT controller will be needed in SUMMER, FALL, WINTER, SPRING, it is needed once the battery is charged, PERIOD.

There are other solutions but by just saying that $20.00 is expensive for the WASTED power, the other solutions are as expensive so let's not talk about them.

NO it is not used for the wasted power it is USED to PROTECT the battery bank and if the battery bank cost is of not concern then just forget the Shunt controller.

And, as well, it is to protect the mill for over RPM limits.

The Shunt regulator you indicated is a basic and stable controller to maintain the proper operating battery voltage for long life.

Regards

Nando

[RobC]

(Keep in mind that Chris Greacen's shunt regulator is only rated at 15 amps.)

 Not a problem just parallel a half dozen power mosfets instead of one. RobC

[TomW]

Ed;

I have friends who make pottery. Broken kiln element wires they cannot use are great for smaller loads [500 watt]. Seems like they buy the coils to fit a certain wattage and when they fail they burn open at some spot near the center  making the 2 halves useless for them. It is not really that expensive new, either.

Just an idea if you know folks that fire pottery with electric kilns it might be worthwhile to ask them. It looks like a long spring and is easy to tap it with a splitbolt anywhere.

Cheers.

TomW

[daleh007]

You can buy different size nichrome wire on e-bay for cheap. Do an internet search on "nichrome wire" and you will find sites such as http://www.wiretron.com/design.html

which will give you some good info on design.

Daleh007

[deloiter]

You could also replace the IRFZ40 with one IRFB3207 Power MOSFET or similar.  The IRFB3207 is rated at 75 volt and 180 amp.  Spec sheet at http://www.irf.com/product-info/datasheets/data/irfs3207.pdf.  Digikey sells them for under $5 in single quantiy, probably cheaper elsewhere.  

[witapple]

I have used plain copper wire as a shunt load several times so in this case I would use something like 175 feet of #14 wire to dissapate around 500 watts (if i quickly did the math right). Yeh I know copper wire isnt cheep but if you have it laying around it is cheeper than buying something.

#14 is about .002524 ohms per foot so you can calculate what you need from that. I run up to 2 and a half times the rated current of regular house wire without no problems as long as it is exposed to air.

[VinceB]

Nando,

We will use the wind generator at our fishing camp, so that's why I said heating elements would be useless because we don't go there during the winter. I know the battery has to be monitored at all times during charging.

[VinceB]

deloiter,

Actually, I was going to order a 55V - 75 Amp  Power MOSFET instead of the IRFZ40.

I suppose it will be more than enough. I will try put a load that will pull around 35 Amp...

Do you have any experience with these Power FETS ? I am thinking of putting a big heat sink. But with so much current through the transistor (package is a TO-220AB!! which is quite small), it will be flaming hot!

[go4it]

I would also like to find an inexpensive shunt controller to use with one of Hugh's mills, but I am not very proficient when it comes to soldering up electronics.  It has been recommended that I get a trace C40, but I am still trying to find something less expensive

[DanG]

Nickle-Chromium wire has a surface resistance greater then its core value from being Temper annealed - if you are mending a element or fabricating one out of nichrome safety wire to get a reliable & safe connection one must spot/resistance weld every joint, crimp connections will develop resistance over time till they fail.

A surplus place near me has 12"x18" panels of aircore wound heater panels for a few bucks each - I've always wondered if wind people would be interested in a few of em..

Some factoids from my referance bookmarks...

Nichrome-60 Wire {NiCr60 #675 Alloy}

Nickel: 57-58% ; Chromium: 16% ; Silicon: 1.5%; Iron: remainder

awg 22     Ohm per 10' 360.0

awg 21     Ohm per 10' 254.4

awg 20     Ohm per 10' 181.2

awg 19     Ohm per 10' 129.6

awg 18     Ohm per 10'  96.0

awg 17     Ohm per 10'  68.4

awg 16     Ohm per 10'  49.0

Ni80/Cr20 Alloy

Al 1000; Cr 18-20%; Fe 2000; Mn 2000; Si 1.5%; Ni+Co remainder

awg=  .25 mm  Resistance range 21.6-21.65 Ohms/m

awg=  .5  mm  Resistance range 5.29-5.33 Ohms/m

awg= 1.0  mm  Resistance range 1.40-1.44 Ohms/m

awg= 2.0  mm  Resistance range 0.327-0.361 Ohms/m.

[deloiter]

I use PMOSFETs in audio and pulse-width applications.  I generally try to use a current rating 4 times my planned max current flow - just a personal preference. You are right about the thermal issues from a small case.  However, in general, the higher the current rating, the lower the ON resistance: .028ohm for the IRFZ40 vs .0036ohm for the IRFB3207.  Thus the power dissapated as heat is inherently less with the higher rated device for any given current flow. Just food for thought.  Good luck. Keep the board posted - we need a cheap, robust shunt dump.  

[paulpic]

To get a much higher current with this circuit,place a 100 amp or so solenoid in circuit as the dump load.Then through the solenoid place your load from the batteries.