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Cephas 6th April 2002 02:31 PM

Where can found R-core Transformer?
Hi .

Where can found R-core Transformer in internet?
I want about 1.2KVA

thanks a Lot..

tvi 6th April 2002 04:30 PM

I believe kitamura-kiden are the originator of the R-core design, don't know any distributor though.


contaxchen 18th September 2003 06:43 AM

There are some cheaper ones manufactured by ECU- TAMURA ELECTRIC CO in China!
It seems like it has nothing to do with the Tamura we know in Japan. But, the price is really economical. Only last a few digits of Japanese product.
:dead: :dead: :dead:

UrSv 18th September 2003 07:05 AM

Cradle22 18th September 2003 07:15 AM


Also try

Dr. Feickert

I bought mine there.



Elso Kwak 3rd November 2004 08:38 PM


Originally posted by Cradle22

Also try

Dr. Feickert

I bought mine there.



Hi Arndt,
How does the R-core compare with toroid or EI-core?

jcarr 3rd November 2004 10:52 PM


May I assume that your application is for power transformers? (The characteristics that are appropriate for 50/60Hz power transformers are definitely not the same as what is recommended for wide-band signal transformers.)

Toroidal transformers have good regulation and low output impedance, but OTOH high interwinding capacitance. High interwinding capacitance means wide bandwidth coupling between the primary and secondary windings. This may not be what you want in an audio power supply, as it implies that all kinds of noise as well as 50/60Hz can pass through the power supply. A toroidal transformer intended for a power supply should have an additional electrostatic shield between the primary & secondary windings, as this helps reduce the primary-secondary noise transmission issue somewhat.

EI (frame) core and R-core transformers usually have split-bobbin primary and secondary windings, which cuts down on interwinding capacitance and makes it considerably more difficult for non-50/60Hz noise components to pass in and out of the power supply. Additionally, R-cores have low levels of radiated magnetic flux and mechanical vibration, which allows them to be positioned closer to sensitive aplification circuitry without causing problems.

FWIW, I have experienced much greater variation in quality with EI-core power transformers than R-cores. I can't recall any R-core power transformer that I have used as having caused problems, but while a good EI-core is also perfectly acceptable, some EI-core transformers have definite quality problems in the areas of hum and vibration, temperature rise, magnetic flux radiation, and so on. It pays to go with a good manufacturer.

With R-cores and EI cores, you can also specify additional electrostatic shielding between the primary & secondary windings for less noise transmission, but this is not as critical as it is when using a toroidal transformer for power supply applications.

Also, EI and R-cores are usually physically larger and heavier for a given VA rating (at a given flux) than a toroidal, and this can have a direct impact on the size and weight of the supporting chassis.

hth, jonathan carr

rcavictim 3rd November 2004 10:58 PM

I've never seen a transformer core shaped like an "R", so what in tarnation are you guys going on about?

Andrewbee 3rd November 2004 11:04 PM

Its not shaped like an "R". the shape is somewhat / kind of/ somewhat like a rectangle but with rounded ends. The "R" stands for racecourse as in horse racing, that is what they use to describe the shape. If you go the link Planet 10 posted you will see them. I bought a pair of the single end RW-20's soon after they first came out.


tubetvr 3rd November 2004 11:17 PM


What are the advantages, (from an users perspective) with using a R-core transformer compared to a C-core? For me they look very similar although I can understand that there are advantages from a mass production perspective i.e. no need to cut the core, polishing the ends and clamp the whole thing together.

Regards Hans

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