Generic name for USA style of mains transformer?

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Not sure if you are referring to a 'flat pack' or a 'C' core transformer. The Flat pack has squared 'U' shaped laminations, so if you look at the core the lams are stacked [like in the common 'EI' tranformer with the coil on the centre leg], but the two coils are on the legs of the'U'. The C core is more like what you describe with the core curved around at each end and is made by winding the lamination strip around a rectangular form, then compressing it on each long side to bond the lam together, then cutting it in half midway along the 'long' side and polishing the cut ends. Two coils are wound in the conventional manner then the core halves slipped in and clamped [we used to use steel band wrapped around the perifery of the core]. The ends could be epoxied together, but that introduced a tiny air gap that affects the core performance. This core design came, originally, from Germany IIRC. I believe that the ones we were using back in the '60s came from Vacuum- Schmeltz [sp?]

Neil S.

the

Not sure if you are referring to a 'flat pack' or a 'C' core transformer. The Flat pack has squared 'U' shaped laminations, so if you look at the core the lams are stacked [like in the common 'EI' tranformer with the coil on the centre leg], but the two coils are on the legs of the'U'. The C core is more like what you describe with the core curved around at each end and is made by winding the lamination strip around a rectangular form, then compressing it on each long side to bond the lam together, then cutting it in half midway along the 'long' side and polishing the cut ends. Two coils are wound in the conventional manner then the core halves slipped in and clamped [we used to use steel band wrapped around the perifery of the core]. The ends could be epoxied together, but that introduced a tiny air gap that affects the core performance. This core design came, originally, from Germany IIRC. I believe that the ones we were using back in the '60s came from Vacuum- Schmeltz [sp?]

Neil S.

"image" searching on "C core " "mains transformer" didn't show any like the one in front of me

is similar but this one has a core more circular in cross-section , or maybe circular , under an all over moulded epoxy-like coating . I will take a pic tomorrow I can't see how the core could be moulded over the joins and then couils placed over, no other bracing strips around the core .

**Sounds like an 'R' core tranny to me. Excellent isolation, but higher loss than a toroidal.

--
Trevor Wilson
www.rageaudio.com.au

**Like these?

--
Trevor Wilson
www.rageaudio.com.au

Yes it would seem R-Core, eg

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I wonder how they are made. Coils formed and laid over the bare cores which are then joined somehow farely seemlessly and then perhaps 4 sections of quartered pre-moulded epoxy covers slid over the cores and under the coils and plastic welded into place

"N_Kook"

** An R-core is wound with one continuous strip of steel - tapering at each end to get a round cross section. The two plastic bobbins are made as halves and glue together around each straight limb of the core.

There are also gear like teeth on the ends of the bobbins - allowing a machine to spin them on the core while an operator feeds them with wire.

Then the bobbins and wire ends are secured and an overall insulation wrap applied.

A steel claming frame is finally attached to allow chassis mounting.

Clever - huh ?

.... Phil

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halves

Ah! its now so obvious, had me scratching my head. I never thought of winding the bobbins while on the core, yes clever. I'd worked out how fully enclosed toroidal transformers with solid cores were wound, a few months back, even made a sort of m/c for doing it, but this type had me flumoxed

On a side matter relating perhaps to their efficiency. The one in front of me gives off various voltages and the associated DCs are marked on the overlay (no schematic available). All the DC voltages , amplifier but just quiescent no load, all the actual DC levels are about 10 percent less than the overlay marked DC. If one of these C or R type cores is knocked/ abused / thermal stress/vibration and the closure face opens up muicroscopically, could that cause a 10 percent drop in secondary voltages?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

"N_Kook"

** Nope.

Look elsewhere for the explanation.

.... Phil

wire.

wrap

actual

of

and

percent

Increase of DC saturation characteristic of iron powder over time? If so that would apply to toroidal transformers also and I've never noticed a 10 percent drop in a toroidal

"N_Kook"

** What " iron powder " ?

Wot an annoying bloody imbecile.

.... Phil