PVI 7200 Dump Load Question

[Milan Slovak]

I have a pvi-7200 wind interface box that I will be hooking up to a 2kw turbine on one side, and a Aurora 3600 on the other.
I need to size some dump load resistors for say 3000 watt peak
The 7200 dumps @ 530 volts
First:
Is this AC or DC?


Second:
I get 530 squared / 3000 watts to give me 94 ohms resistance needed?

So (3) 1000w 31ohm resistors in series.

Correct?

Can I purchase these anywhere pre-made in an exterior enclosure?

Thanks for help.

[Rob Beckers]

Hi Milan,

The dump circuitry is after the rectifier, so it's 530V DC.
Your calculation for resistance is correct. If you find a North American source for dump loads please let me know. I've been importing them from Korea, and they are not cheap.

-RoB-

[Milan Slovak]

here is the link to resistors.
They are about $50 per.

Put in Huntington Electric as the mfgr and 1000 watts.
It will come up with a list of different ohm resistors.

These will need to be put in some sort of metal heat resistant enclosure though.


M

[Milan Slovak]

http://search.digikey.com/scripts/DkSearch/dksus.dll

forgot the link.

[Brian McGowan]

This is the only resistor they have in stock and you would need 3 and you would still be a little shy on resistance and right at the edge of power. Note the price!

Digikey part# TA1K0PH30R0KE-ND 30 ohm 1000W Price $169.46

The cheapest resistor is

Digikey part# 1-1879453-9-ND 33 ohm 1000W Price $41.18 Minimum order 10


I have thought about this and I have decided that if I need a dump load of any significant size I will build one out of heating elements from broken hair dryers. My thought was to get a square or rectangular piece of heating duct, mount hooks with threaded ends in opposite sides near one end, put a round ceramic insulator on each hook and then unwind the heating elements from their holders and run them in a zigzag fashion between the hooks, stand the duct upright with the elements at the bottom and a space at the bottom for air to flow in and chimney effect should cause air to flow. If air does not move fast enough add a fan to blow air into the bottom. You would have to figure out the proper series parallel arrangement for the heating elements based on their power and voltage for the country you are in. To dissipate 3000W for me here in the US with 120 volt 1000W hair dryers I think I would need 6.5 elements in series to come up with the proper resistance and they would be operating at about half their rated wattage for a safe arrangement with plenty of headroom. I figure they are already made to convert electricity into heat and they are plentiful and cheap or free. I already have 3 on my workbench now and I am sure I could get more if I asked all my female acquaintances and family members.
Just a thought
Brian

[Rob Beckers]

Brian, what is the regular working voltage of turbine? I'm just wondering if letting it run up to 530V DC before adding the dump load is going to work at all in keeping it under control. If the working voltage of the turbine is much lower you could make a nice 3-phase AC dumpload out of more commonly available items, such as baseboard heaters.

-RoB-

[Brian McGowan]

Rob,
I was going off the voltage Milan was talking about. My little turbine is just 12 volts. I have a handheld car window defroster which plugs into a CLA and draws 12.5 amps and a 12 VDC hairdryer that also plugs into a CLA and draws 18 amps for my dump loads although I try to use the power for useful things when I am home and see the dump load working. I was hoping to make an arrangement where these loads were switched in to match the power I needed to dissipate so I could have a possible 12.5 amps or 18 amps or 30.5 amps of load. As you may have seen in another post I made recently, I am also considering using a 400W grid tie inverter for a dump load. I still have to think on that one some more.

I won’t even get into how fiercely disappointed I am with the total lack of system level control available at this time in this industry. There is no central “brain” in charge of all the system components. I have tried to pass my ideas along to major equipment manufacturers with no luck because I feel they are in a better position to implement them but if they won’t do it I will. I program control systems for a living that are well suited to do this.

I did write a whole long thing yesterday but when I went to post it I was asked to sign in again and I didn’t copy and paste my spiel to somewhere else before I tried to sign in again and it lost all of it so what showed up was an abbreviated version.

In part 2, I did talk about baseboard heaters and how it would be easy and probably cheap to just get outlet boxes and outlets and wire them up in whatever series and/or parallel arrangement was needed to cover your power output and just plug the baseboard heaters into them. I thought if you had one of those baseboard heaters with the single element that looks like a rod in the system you could attach a wire to the electrical connection at one end or the rod and clamp the wire to the rod with the hose clamp which would give you some adjustment by sliding the hose clamp along the rod until the proper resistance is achieved much like a big wire wound ceramic adjustable resistor.

That’s my thoughts
Brian

[Rob Beckers]

Brian, you have lost me...
You want to use a PVI-wind-box and a 530V dump load for a 12V battery charging wind turbine? Hopefully I got that wrong. If not, it won't work. Your turbine will be long gone by the time it reaches 530V, flown to bits.

As to the posting issues: Unless you check the "remember me" box upon logging in, the forum will log you out after 15 minutes of no activity. I'm not too sure what happens if you try to post while logged out. Ideally it should ask your to log in and then post. Seems that's not happening, and unfortunately I can't change that. Using the 'back' button of your browser should get your post back though, so you can copy the text to the clipboard (and re-post it after logging in).

-RoB-

[Brian McGowan]

Rob,
Milan, who started this thread, wants to use the PVI-wind-box and a 530V dump load. I was attempting to help him.

My turbine is small and 12 volt and I have my situation more or less covered.

Thanks for the "remember me" tip. There are other places besides your site where this happens to me and I usually type out my responses in Word and then copy and paste them. I neglected to do that this time and I paid for it.

Brian

[Cor van Houtum]

Hello Milan,

most 2kw turbines are rated at 120 volts
in practice they do about 210 volts when the nominal power of 2kw can be delivered
I have seen myself that our 2kw turbine on a aurora 3600 can do more then 3600 watt when in a high storm .

we dump this engine at a voltage of 250 volt DC

If you use a aurora windinterface then it will brake at the 530 volts that are preset in the interface.
But when your generator goes up to 530 volts it will loose the blades in storm.
then the interface does not brake the generator when the grid fails.
this is bad enginering in my opinion


So do not use the aurora interface to brake the turbine
only use this thing to rectify
put on a self made relais based dumpload system on the turbine and use a omron measurement relais to do the steering trick.

The dumpload relais should be big and from the type that makes contact when NO power is available.
this means that the generator is stopped when you have a grid failure.


good luck

[Cor van Houtum]

when dumped on 250 volts then you need 3000 watts 20 ohms

best is to use 3 resistors and put them over the ac 3phase
you can leave 1 phase always connected and switch the other 2 phases over the relais
double connection offcourse.

put them in a triangle over the gen.

[Cor van Houtum]

sorry forgot to mention,
when you put them in a triangle over the 3phase
then you need 3 pcs of 1000 watts with 60 ohms a piece offcourse

[Rob Beckers]

. . . then the interface does not brake the generator when the grid fails . . .

Just one little correction: The PVI-wind-interface doesn't use a power supply, it gets its power from the wind turbine. So, it will actually work fine when the grid fails, and switch on the dump load at 530V. I agree with Cor though that for many/most wind turbines that's much too high a voltage.

-RoB-

[Cor van Houtum]

And this is exactly why it is not working correct,
you are absolutely right Rob,

The aurora interface is build to protect the inverter but it has no relation what so ever with the windturbine.

Then in my opinion it makes no sense to let a windturbine spin when there is a power grid failure.
it has to stop immidiatly when loosing the grid on the system.
this is also a feature that is not build in the aurora.

And the dump attack voltage should be adjustabel to the needs of the turbine
and not on a 530 set voltage.

So this leaves you with a nice rectifier unit that carries the name of windcontroller
but it is not.

For the SWG turbines my advice is to get rid of the aurora interface
it gives a false safety idee to the users.

[John Szegda]

Hello Cor,

Have you worked with the Exmork Controllers and what is your opinion of these units.

John

[Cor van Houtum]

Sorry John this one I can not help you with (not yet)
But most controllers are look a likes so ask and i will try !!

[Milan Slovak]

Yes, I was trying to use the Wind Interface dump @ 530 V to release to the resistors to protect the unit.
The turbines themselves have the furling for decoupling them, and some have the electromagentic brake.

Has anyone hooked up (2) turbines to (1) PVI 7200 interface??

M

[Ken Hall]

Rob,

Milwaukee Resistor made my dump load. They'll provide an enclosure.

Ken