[Test-Equipment] Rewind a transformer!

[David]

I do the same thing for an already wound transformer.

When building a new one, I usually measure the magnetizing current or
inductance versus frequency to determine how many turns one winding
will require if I lack a data sheet listing the peak magnetic flux
versus frequency of operation and the AL.

Didn't he mention something about the core he used being designed for
prototyping?  I thought that was pretty slick.  I am using to winding
my own for switching applications.

On Wed, 13 Feb 2013 20:33:23 -0700, Mike Manes <mrmanes at gmail.com>
wrote:

>He mentioned coming up with a volts-per-turn figure in order
>to determine the number of secondary turns, but if he muttered
>how he did that, I missed it.  The way I do it is to wind a
>known number turns on the core, fire it up and measure the
>secondary voltage.  10-20 turns will probably do for a mains
>freq xformer, and only 1 or 2 on a HF device.
>
>What I found neat was his layering tool.  I do that with great
>tedium manually, and an occasional unwind if I mode too fast or
>slow.
>
>73 de Mike W5VSI
>
>On 2/13/13 6:13 PM, Randy D. Hunt wrote:
>> On 2/13/2013 1:08 PM, David wrote:
>>> On Wed, 13 Feb 2013 10:14:40 -0800, "Randy D. Hunt"
>>> <randy_hunt960 at yahoo.com> wrote:
>>>
>>>> On 2/12/2013 11:12 PM, Dave C wrote:
>>>>> http://www.youtube.com/watch?v=ZVSbt5q0KF8
>>>>>
>>>>> Very creative...
>>>>>
>>>>> Dave
>>>>> ______________________________________________________________
>>>>> Test-Equipment mailing list
>>>>> Home: http://mailman.qth.net/mailman/listinfo/test-equipment
>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>> Post: mailto:Test-Equipment at mailman.qth.net
>>>>>
>>>>> This list hosted by: http://www.qsl.net
>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>
>>>> I like the idea of the transformer kit.  Did anyone notice the
>>>> difference in the amount of iron in the core as compared to the stock
>>>> transformer.  I would say the kit has about 2/3rds of the iron.  This
>>>> could be making his transformer run hot thereby causing him to have to
>>>> rewind it. . .  Just a thought.
>>>>
>>>> Randy, KI6WAS
>>> Presumably he adjusted the number of primary and secondary turns while
>>> keeping their ratio constant to achieve the recommended magnetic flux
>>> density at 50 Hz if the cross sectional area was different.
>>>
>>> Only two of the windings were moved to the transformer.  He kept the
>>> old one with those two windings removed and placed the primaries of
>>> both transformers  in parallel.
>>
>> Oh, yes, 50Hz.  I forgot about the lower line frequency. . .