Petter help

[potter]

I have just put the gen head back on my Petter find and can use some help.On start up I had to flash the field it now starts putting out fine but with a max of 101-202 volts at 60 hz.Is there a simple fix or does this mean that I have a bad field winding and should just give up.

      Thanks Potter

[Thob]

That fresh coat of white paint sure makes it look good - I wouldn't give up just yet.  Can you post the information from the tag on the generator?  Do you have a wiring diagram?

Most likely there are one or more adjustments for voltage on the generator, but you need to know what kind you have to know how to adjust it.  If you post the information, probably someone here can help.

[potter]

Thanks Thob,Its an old Winpower CM12P4C I do not have a wiring diagram.It is using a 110 leg through a diode bridge to power the main field winding and also a current transformer to power a compensating field winding .There are no adjustments the only thing that I am not to sure of is they have a small cap across the diodes I think this is to protect the diodes

  thanks Potter

[Thob]

Hopefully, someone on here is familiar with this type of generator.

You might check the transformer closely - does it have an adjustable gap?  The ones that are adjustable have an "E" shaped piece, with the windings around the center leg of the "E"; and an "I" shaped piece that can be moved closer and farther from the "E" shaped piece.  There may be shims (plastic or paper) between the two and slotted holes that mount one side.  Increasing the gap should increase the no load voltage.  Non adjustable transformers have the laminations overlap each other, alternating sides between the "E" and the "I" as the laminations are stacked up.

Every time I think I have generators figured out, someone comes up with yet another new regulation scheme.

[BruceM]

I sure enjoy and appreciate your posts, Thob.  Adjustable gap transformer is a new one to me. It is surprising  how many ways there are to regulate generator head voltage.

Potter is this unit a brushed head?  Cleaning up the commutator and checking for bad connections or nearly broken wires (high resistance) in the excitation side might help too. Pity you don't have data on the unit so the field coil resistance could be checked.

An AVR off of 240VAC would eliminate the problem of a failed compensator, and would overcome some increased resistance in the brush/field coil side.  But the compensator should have no role in no load voltage regulation...

I hope someone will know more about Winpower heads.

[potter]

Thanks Bruce no all is clean and tight I had this striped completely down, Do you think a capacitor across the field windings would help,or one of the inexpensive 220 volt AVR from Tom Orsbern ?.   

    Thanks Potter                       

[potter]

Sorry yes this is a brushed head

[mobile_bob]

winco used the transformer controlled method for years and years, i would do as Thob stated
and check it closely because my bet it is adjustable.

it takes very little adjustment to shift the voltage up and down.

the advantage to this method of regulation, is they have a much larger surge capacity than do the harmonic excited genheads

we had a discussion regarding this method a couple years back,

bob g

[mobile_bob]

my apology, the discussion about this method or regulation was done off board

somewhere i have a pdf describing the theory of operation, and method of adjustment that winco among others used.

let me see if i can find it.

bob g

[mobile_bob]

found the discussion, i was wrong, we did discuss it here

http://www.microcogen.info/index.php?topic=1604.0

bob g

[mobile_bob]

http://www.firstallpower.com/news/item_420.html

check out the whi series

450% surge capability for up to 7 seconds for tough to start loads

i know that winco has the adjustment procedures online somewhere, i have a copy somewhere but can't find it just now.

bob g

[BruceM]

Thanks for the link, that was a very good thread, BobG. 

Doesn't an AVR effectively do the same thing with no special windings and transformers, boosting the applied field excitation to try and maintain the proper output voltage?

Of course I'd be thrilled to have one of these heads with this system, as I suspect they would be well regulated and surge load capable sans electronics. But I think this system in itself will not give you any extra load starting capacity compared to a good AVR, for the same head and engine.

Unless I'm missing something...

[mobile_bob]

here is an ST head that uses the transformer control scheme
if you notice on the upper right side of the lamination core stack
there is a shim sticking out, the thickness of this shim sets the airgap
which sets the output voltage.

http://www.utterpower.com/the-folk-alternator/

bob g

[mobile_bob]

BruceM

its been a while since i read up on this system, so i might not remember accurately what i think i learned 

from what i recall, the transformer has two main primary windings, one to provide basic excitation much like we do with
the addition of such to provide for isolated excitation power...
the other winding is a heavy current winding, which is in series with the load output, this effectively increases the flux in the core
inline with the additional current flowing to the load.

basically the transformer is a compound unit, the heavy current winding augments to standard primary and in doing so increases the output
voltage in the secondary, which is fed to the rectifier and then the field.

i think these were very popular before the advent of economical AVR's coming on the scene, however they are still in use in certain applications
where brute force, robust control and where voltage control doesn't have to be .01% of a gnats hair.

back when this topic first came up, i inquired about the scheme on a power forum, and got the skinny from a dude that has been in the biz for a very long time. his take is they were and are still used as a butt simple, fairly accurate, and tough as nails regulation scheme for mid and larger generators.

from what else i can  gather they are a step up from harmonic winding excitation, and a step below AVR if you need super accurate voltage regulation. they seem to shine in appications where power factor is less than optimum.

i would really like to get my hands on one of the ST's with the transformer system, to see what all the fuss is about.

bob g

[potter]

I have tried a few caps that I had laying around to see what would happen.I first tried a 200 volt 330uf and had an increase of 6 volts no load but under load it lost 3 volts,I then paralleled two together this ran cooler with about an additional 2 volts but still a small drop under load and a spike when load was dropped.I then tried two 200 volt 2200 uf caps and got111volts unloaded under load it jumped to 115 volts and no spike when load was dropped .I think this may work anyone care to give a guess as to what caps may give me 120 volts .

      Thanks Potter