I need to get some basic transformer theory help

[gav]

hello,
this may be a stupid question but...

Is it possible to run a mains (50hz) power transformer at a much higher
frequency or will it become very inefficient (are there increased hysteresis
losses) ? I'm talking 150hz-10khz or so.

I don't think it will be able to but don't understand the theory.

Gavin.

 

[Phil Allison]

"gav" <get@lost.com> wrote in message news:biflkf$5nq$1@lust.ihug.co.nz...

hello,

this may be a stupid question but...

** Wise disclaimer....

Is it possible to run a mains (50hz) power transformer at a much higher
frequency or will it become very inefficient (are there increased
hysteresis
losses) ? I'm talking 150hz-10khz or so.

** Depends on the transformer. For most E-core types losses will
increase above about 400 Hz - due mostly to leakage inductance. For
toroidals the frequency range is much higher - to 10 kHz at least and 100
kHz in some cases.

Where exactly did you expect to find 240 volts at 10 kHz ??



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

 

[Adrian Jansen]

No, transformers are optimised for a specific frequency range. In general,
operating at any frequency outside around 10% lower, and 100% higher in
frequency will severely degrade performance. Get a good basic book on
electronic theory, and you will learn why.

--
Regards,

Adrian Jansen
J & K MicroSystems
Microcomputer solutions for industrial control
"gav" <get@lost.com> wrote in message news:biflkf$5nq$1@lust.ihug.co.nz...

hello,
this may be a stupid question but...

Is it possible to run a mains (50hz) power transformer at a much higher
frequency or will it become very inefficient (are there increased
hysteresis
losses) ? I'm talking 150hz-10khz or so.

I don't think it will be able to but don't understand the theory.

Gavin.

 

[Phil Allison]

"Adrian Jansen" <qqv@noqqwhere.com> wrote in message
news:3f4be2ab@duster.adelaide.on.net...

No, transformers are optimised for a specific frequency range. In
general,
operating at any frequency outside around 10% lower, and 100% higher in
frequency will severely degrade performance. Get a good basic book on
electronic theory, and you will learn why.

** A book on "electronic theory" will not give much info on mains
transformers, better get one on electrical theory.

There is no problem with most E-I transformers at 400 Hz and all
toroidals go fine to 10kHz - at least.

Only split bobbin designs have high leakage reactance.




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

 

[gav]

Where exactly did you expect to find 240 volts at 10 kHz ??

I don't know. But mains 50hz transformers are easy to get my hands on at
jaycar.
I need it for step up in any case.
Gavin

 

[Phil Allison]

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

Where exactly did you expect to find 240 volts at 10 kHz ??

I don't know. But mains 50hz transformers are easy to get my hands on at
jaycar.
I need it for step up in any case.

** Trying to make some big sparks ??

Nicola Tesla style ?



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

 

[gav]

** A book on "electronic theory" will not give much info on mains
transformers, better get one on electrical theory.

-any recomendations? I'm doing an electrical apprenticeship and my books
don't go much beyond turns ratio/voltage calculations.

 

[gav]

If you're thinking of several KHz or higher, then Amidon sell some really
chunky ferrite toroids that make great trannies.

I meant 150hz-1khz.. oops.

thanks but.
gavin

 

[Adrian Jansen]

Much simpler to make DC out of it, using the alternator built-in rectifier
and a battery, then a DC-DC converter to get the voltage you want. Avoids
all the tricky problems of regulating the alternator so you dont blow up the
transformer. Not to say those of designing a special transformer to cover a
wide frequency range and voltage input as well.

--
Regards,

Adrian Jansen
J & K MicroSystems
Microcomputer solutions for industrial control
"gav" <get@lost.com> wrote in message news:bii1hf$7f6$1@lust.ihug.co.nz...

** Trying to make some big sparks ??

Nicola Tesla style ?


I'm embarrassed to say as it's probably not possible.
but I'm trying to get +-60v rails out of a standard car alternator as
efficiently and cheaply as possible.
I'm hoping I can take 20vAC line voltage off two phases (between
150-1000hz)
step up with a couple of toroidals and rectify.
Apart from my transformer problem I'll need to make a regulator to drive
rotor winding and keep it at 60v

But I'm learning by experimenting at the moment with very limited theory.

Any input appreciated
gavin

 

[gav]

"Adrian Jansen" <qqv@noqqwhere.com> wrote in message
news:3f4d3f66$1@duster.adelaide.on.net...

Much simpler to make DC out of it, using the alternator built-in rectifier
and a battery, then a DC-DC converter to get the voltage you want. Avoids
all the tricky problems of regulating the alternator so you dont blow up
the
transformer. Not to say those of designing a special transformer to cover
a
wide frequency range and voltage input as well.

Wheres the fun in that
thanks anyway.
gavin