Re: Ferrite Cores - Where's the Gap? (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 7 Apr 2004 14:14:44 -0600
From: Gomez Addams <gomez@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Ferrite Cores - Where's the Gap? (fwd)

On Apr 7, 2004, at 2:29 PM, High Voltage list wrote:

> Original poster: Steven Roys <sroys@xxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Wed, 7 Apr 2004 18:27:48 +1200
> From: Malcolm Watts <m.j.watts@xxxxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: Ferrite Cores - Where's the Gap? (fwd)
>
> On 6 Apr 2004, at 20:38, High Voltage list wrote:
>
>> Original poster: Steven Roys <sroys@xxxxxxxx>
>>
>>
>>
>> ---------- Forwarded message ----------
>> Date: Tue, 6 Apr 2004 10:09:36 -0600
>> From: Gomez Addams <gomez@xxxxxxxxxxxx>
>> To: High Voltage list <hvlist@xxxxxxxxxx>
>> Subject: Re: Ferrite Cores - Where's the Gap? (fwd)
>>
>> On Apr 5, 2004, at 10:51 PM, High Voltage list wrote:
>>
>>> Date: Mon, 5 Apr 2004 18:20:34 +1200
>>> From: Malcolm Watts <m.j.watts@xxxxxxxxxxxx>
>> [snip]
>>>     A flyback supply will always have a gapped core since energy
>>> transfer is accomplished by storing energy in the core (an
>>> undesirable property in pushpull and bridge topologies) and the core
>>> material itself will store very little energy without going into
>>> saturation. Despite the undesirable side-effects of gapping in other
>>> types of supply, transformers used in forward converters, bridge
>>> converters etc. will often also have some core gapping to obviate
>>> flux staircasing.
>>
>> So, to paraphrase the old Wendy's commercials... "where's the gap?"
>
> If the question is serious rather than rhetorical, the answer is: if
> there is no gap in the core, the supply it came out of was not a
> flyback supply.

  If it looks like a flyback transformer, and it came out of a TV or a
computer monitor, what then do suppose it is?

> Are the core ends firmly pushed together with no
> spacer material (e.g. paper, card etc.) in between the pole pieces?

Yes.

> If the answer is "yes", then the core isn't gapped.

Exactly my point.

>       HV and EHT supplies are not always flyback supplies. For
> instance, many of the so-called flyback supplies built by people in
> this circle are actually self-oscillating forward (often pushpull)
> converters. Sorry if this sounds like pure pedantry but this is an
> engineering forum of sorts and it is helpful to get accurate
> descriptions of equipment to facilitate long-distance troubleshooting.

  Thanks for your input.  I know very little about TV flyback
transformers,
but I do know what I've taken apart and what I've seen...