Transformer experiments.

[gav]

hello.
I need a 1:2 step up transformer to go from 20V to 40V at around 160VA.

Is it possible to purchase such a transformer?
Am I able to purchase suitable toroidal cores and copper and wind my own?
Is this outside what a beginner is capable of?

any help appreciated
Gavin.

 

[Phil Allison]

"gav" <get@lost.com> wrote in message news:bivha8$i1m$1@lust.ihug.co.nz...

hello.
I need a 1:2 step up transformer to go from 20V to 40V at around 160VA.

Is it possible to purchase such a transformer?

** Is this still for the car alternator idea ????

You had better make *damn sure* of the lowest AC frequency that
alternator will produce - even during engine cranking - or any attached
transformer will magnetically saturate and draw * huge* current from the
thing.




........... Phil

 

[gav]

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f534acd$0$28117$afc38c87@news.optusnet.com.au...

"gav" <get@lost.com> wrote in message news:bivha8$i1m$1@lust.ihug.co.nz...
hello.
I need a 1:2 step up transformer to go from 20V to 40V at around 160VA.

Is it possible to purchase such a transformer?


** Is this still for the car alternator idea ????

haha, sure is.

You had better make *damn sure* of the lowest AC frequency that
alternator will produce - even during engine cranking - or any attached
transformer will magnetically saturate and draw * huge* current from the
thing.

Didn't think of that, although I suppose you gathered that.

I'm really only interested (at the moment)in seeing what sort of power i get
out of a 3 phase alternator when using only 2 phases compared to it's
normal setup.

I'd love to experiment with toroidal core windings if it is not too
expensive excersise. I imagine it may be too complicated.

I managed to get a regulator circuit working for the thing using a couple of
old PC motherboards for parts. I sort of understand how it works but have a
feeling (from my limited education on the subject) that it needs some
refinements. I had to replace parts until it regulated at the voltage I
wanted and think it relys totaly on the beta value of the 1 transistor in it
and that this may pose a problem as it heats up. If I can work out the
component symbols to draw a circuit diagram of this I'm sure someone here
could point out any likely problems at a glance.

So phill,
can I get a core and start winding or is it more difficult than that?

thanks
Gavin

 

[Phil Allison]

"gav" <get@lost.com> wrote in message news:bivmv9$lgd$1@lust.ihug.co.nz...

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f534acd$0$28117$afc38c87@news.optusnet.com.au...

"gav" <get@lost.com> wrote in message
news:bivha8$i1m$1@lust.ihug.co.nz...
hello.
I need a 1:2 step up transformer to go from 20V to 40V at around
160VA.

Is it possible to purchase such a transformer?


** Is this still for the car alternator idea ????

haha, sure is.


You had better make *damn sure* of the lowest AC frequency that
alternator will produce - even during engine cranking - or any
attached
transformer will magnetically saturate and draw * huge* current from the
thing.

Didn't think of that, although I suppose you gathered that.

I'm really only interested (at the moment)in seeing what sort of power i
get
out of a 3 phase alternator when using only 2 phases compared to it's
normal setup.

I'd love to experiment with toroidal core windings if it is not too
expensive excersise. I imagine it may be too complicated.

I managed to get a regulator circuit working for the thing using a couple
of
old PC motherboards for parts. I sort of understand how it works but have
a
feeling (from my limited education on the subject) that it needs some
refinements. I had to replace parts until it regulated at the voltage I
wanted and think it relys totaly on the beta value of the 1 transistor in
it
and that this may pose a problem as it heats up. If I can work out the
component symbols to draw a circuit diagram of this I'm sure someone here
could point out any likely problems at a glance.

So phill,
can I get a core and start winding or is it more difficult than that?

** Answer my query about the lowest operating frequency - that is where
the design of a tranny must start.





........... Phil

 

[gav]

approx 50-100hz

I can't be sure as I'm only guessing the pulley ratios at the moment using a
drill and 110mm hole saw and belt.
but if the min frequency is where the design starts then I had better get it
right.

thanks for the prompt response
gavin

 

[legg]

On Mon, 1 Sep 2003 23:26:59 +1000, "gav" <get@lost.com> wrote:

hello.
I need a 1:2 step up transformer to go from 20V to 40V at around 160VA.

Is it possible to purchase such a transformer?
Am I able to purchase suitable toroidal cores and copper and wind my own?
Is this outside what a beginner is capable of?

any help appreciated
Gavin.

If all you need is step-up, without isolation, a mains transformer
with two >=20V / >=4A windings could be configured as an
auto-transformer. Just use the secondaries.

A bit of a waste of space, but probably pretty easy to find in most
places. Cover up the the normal HV primary terminals to avoid
accidents (or use it...).

RL

 

[Phil Allison]

"legg" <legg@nospam.magma.ca> wrote in message
news:6hu6lv4q97pilcpqepo2l5pbshu06be2iv@4ax.com...

On Mon, 1 Sep 2003 23:26:59 +1000, "gav" <get@lost.com> wrote:

hello.
I need a 1:2 step up transformer to go from 20V to 40V at around 160VA.

Is it possible to purchase such a transformer?
Am I able to purchase suitable toroidal cores and copper and wind my own?
Is this outside what a beginner is capable of?

any help appreciated
Gavin.



If all you need is step-up, without isolation,

** Isolation is required.




........... Phil

 

[gav]

If all you need is step-up, without isolation, a mains transformer
with two >=20V / >=4A windings could be configured as an
auto-transformer. Just use the secondaries.

Never thought of that.

 

[gav]

I'm getting more interested in the workings of a transformer than the
practicality of my application.
Stepping away from my alternator experiments for a minute....

What is the cost in winding your own transformer. Is the core the expensive
part and the insulated windings cheap? If so I would like to get myself a c
type core and a kilometer of insulated copper and a book on the subject (if
google provides nothing tonight) and play with it.

Anybody have any recomendations about where I can get any of this stuff?

 

[Mark Harriss]

gav wrote:

I'm getting more interested in the workings of a transformer than the
practicality of my application.
Stepping away from my alternator experiments for a minute....

What is the cost in winding your own transformer. Is the core the
expensive part and the insulated windings cheap? If so I would like to get
myself a c type core and a kilometer of insulated copper and a book on the
subject (if google provides nothing tonight) and play with it.

Anybody have any recomendations about where I can get any of this stuff?

Neosid sell small quantities of ferrite cores up to the size of units used
in TIG welders. I bought copper wire from my electrical store (L&H) either
you buy a 5 kilo spool or you had to buy a partially used 25 Kg spool of
whatever you wanted, then remove what you want to the nearest kilo and then
take it back for a credit on the remainder. Cost about $8:90 a kilo from
memory in 2000.

 

[gav]

Neosid sell small quantities of ferrite cores up to the size of units used
in TIG welders. I bought copper wire from my electrical store (L&H) either
you buy a 5 kilo spool or you had to buy a partially used 25 Kg spool of
whatever you wanted, then remove what you want to the nearest kilo and
then
take it back for a credit on the remainder. Cost about $8:90 a kilo from
memory in 2000.

Thanks, might be easier for me to buy a large toroidal from jaycar, rip off
there windings and get myself some magnetwire from L&H. Unless someone else
sells the cores here in melbourne. Might send Neosid an email.

thanks again,
gavin.

 

[Phil Allison]

"gav" <get@lost.com> wrote in message news:bj6u4v$2va$1@lust.ihug.co.nz...

Neosid sell small quantities of ferrite cores up to the size of units
used
in TIG welders. I bought copper wire from my electrical store (L&H)
either
you buy a 5 kilo spool or you had to buy a partially used 25 Kg spool of
whatever you wanted, then remove what you want to the nearest kilo and
then
take it back for a credit on the remainder. Cost about $8:90 a kilo from
memory in 2000.



Thanks, might be easier for me to buy a large toroidal from jaycar, rip
off
there windings and get myself some magnetwire from L&H. Unless someone
else
sells the cores here in melbourne. Might send Neosid an email.

** Ferrite cores are not even vaguely in the game you are playing with.




............ Phil

 

[gav]

** Ferrite cores are not even vaguely in the game you are playing
with.

 

[Clifford Heath]

gav wrote:

Thanks, might be easier for me to buy a large toroidal...

I don't know what your effiency target is, but if you aren't too
concerned about that you might consider playing with an MOT (Microwave
Oven Transformer). Read up first though, removing them can be lethal
even long after the oven has been turned off.

Anyhow they are EI cores with windings side-by-side. You can remove
the high voltage winding in one of two ways:
* chisel the two sides off and punch out the remaining wire from the core
* bolt the core laminations with two through bolts (there are usually
suitable holes present. Then using a metal-abrasive blade in your power
saw, grind out the welds joining the E and I parts - the weld only runs
a couple of mm deep otherwise it would pass excessive eddy currents.
Then the I core drops off and you can pull the HV winding off intact
with its insulating bobbin. Wind a new winding on the bobbin, rebuild the
xformer and Bob's your mother's brother. Typical ratios give up to one
volt per turn.

You can buy winding wire on 3Kg spools (sometimes even partial spools)
from Australian Isola Materials <http://www.isola.com.au/> for little
more than the copper price (about $22/kg) when I did it earlier this
year. Slight premium for extra fine wire, like the AWG42 I'm using for
winding guitar pickups (60 microns, 100km/3kg!)

Clifford.

 

[gav]

Thanks. I just want to experiment. Not too fussed about the results.
Now, just have to check when hard rubbish is.

gavin.

 

[Mark Harriss]

Phil Allison wrote:

** Ferrite cores are not even vaguely in the game you are playing
with.
............ Phil

Just how low is he going Phil? Neosid F5A doesn't look to bad
and F6 ferrite is made for arc welder impeder bars (50Hz) and speaker
crossovers (30Hz??). He can always ask them for advice.

Mark Harriss

 

[Phil Allison]

"Mark Harriss" <ningauble@REMOVETHISbigpond.com> wrote in message
news:cDZ5b.84057$bo1.13126@news-server.bigpond.net.au...

Phil Allison wrote:


** Ferrite cores are not even vaguely in the game you are playing
with.
............ Phil

Just how low is he going Phil?

** That is something he has no clue about.


Neosid F5A doesn't look to bad

and F6 ferrite is made for arc welder impeder bars (50Hz) and speaker
crossovers (30Hz??).

** Where do you get these silly ideas from ?

Ferrite is no where near laminated silicon steel for transformer
cores.




........... Phil

 

[Mark Harriss]

Phil Allison wrote:

** Where do you get these silly ideas from ?

Ferrite is no where near laminated silicon steel for transformer
cores.
........... Phil

The flux density is nowhere near as good as silicon steel but
a bigger core will fix that. The guy I spoke to at Neosid mentioned
"C" cores they stacked in groups of four for stick welders, i.e. 50Hz
when I enquired about large cores. You'd think a car alternator would
output around 1KHz based on the interference noise you sometimes hear
on a hear car radio, that should be fine for a ferrite tranny.

Speaking of silly ideas about ferrites, I seem to remember some
of yours being put to rest by an American who was more knowledgable about
switchmode transformer design than you. I'm glad I listened to him that
time round.

Regards
Mark Harriss

 

[Phil Allison]

"Mark Harriss" <ningauble@REMOVETHISbigpond.com> wrote in message
news:2i06b.84374$bo1.26014@news-server.bigpond.net.au...

Phil Allison wrote:


** Where do you get these silly ideas from ?

Ferrite is no where near laminated silicon steel for
transformer
cores.
........... Phil



The flux density is nowhere near as good as silicon steel but
a bigger core will fix that.

** Absurd idea based on the error below.


The guy I spoke to at Neosid mentioned "C" cores they stacked in groups of
four for stick welders, i.e. 50Hz

when I enquired about large cores. You'd think a car alternator would
output around 1KHz based on the interference noise you sometimes hear
on a hear car radio, that should be fine for a ferrite tranny.

** That is a wild guess.

The lowest frequency is going to be to be much lower than 1kHz.

Speaking of silly ideas about ferrites, I seem to remember .....

** .... things the way you want to remember them.



............ Phil

 

[gav]

I get 150hz at a simulated idle speed of 900rpm using my crude pulley
setup.
I figure at 6000rpm I'll get 1000hz

I'm using line voltage off 2 star connected windings.

I don't want to be doing any advanced inductor modelling, I just want to
build something that will work for now.
I can probably disconnect the transformer until engine is started.

So, for arguments sake lets say 150hz-1000hz

thanks so far everyone. If your sick of seeing my piss-ant transformer
posts then let me know. Theres probable a newsgroup for begginners like me
somewhere.

gavin.