The three transformers have matching wiring colour codes.
Each limb of the Rcore has a half primary and half of the secondaries on it.
i.e. the half primary is close coupled to the half secondary. This is the correct way to build an Ccore and an Rcore.
The two labeled transformers show:
30VA
Primaire: 117Vx2 Bleu / Noir
Secondaires: 18Vx2 Bleu / Jaune
. . . . . . . . . 18Vx2 Rouge / Blanc
Ecran electro-statique: Masse Noir
One primary is wire coded Blue/White, the other primary is wire coded Blue/White
For conventional wiring to 110/120Vac one would connect the two Blue wires to Mains Live/Hot and connect the two White wires to Neutral/Cold
and
for 220/240Vac one would connect Blue of one primary to the White of the other primary. Then connect the Blue wire to Mains Live/Hot and connect the White wire to Neutral/Cold
NO !!!!!
the blue and white do not indicate the phasing of the windings. All three transformers are colour exactly the same way, so it's not a building error.
For 220/240Vac the two white wires are connected.
Then the Mains Live goes to one Blue and the Mains Neutral goes to the other Blue.
The same phasing error occurs on the secondaries.
One limb has two windings Blue/Yellow and Red/Black. Connect Yellow to Red for a series connection (in this case 36Vac) and then Blue and Black are the output.
Repeat for the other limb with it's pair of secondaries.
Now for a dual polarity supply where the windings are series connected, one needs to connect the two Black wires.
The 72Vac output is from the two Blue wires.
This is the same for all three Rcores from selectronic.
The 120VA Rcore came without any labeling. Fortunately the colour coding is identical to the 30VA
I cannot understand why the manufacturer, Shilchar, has coded the two limbs differently for phase.
I cannot understand why Selectronic does not state that one limb (both primary and secondaries) are out of phase with the other limb.
Have any of you found the same, or was the phasing correctly coded on your Selectronic/Shilchar Rcores?
Use a Mains Bulb Tester to check the primary wiring. A Variac does not prevent damage with this wire coding error.
Each limb of the Rcore has a half primary and half of the secondaries on it.
i.e. the half primary is close coupled to the half secondary. This is the correct way to build an Ccore and an Rcore.
The two labeled transformers show:
30VA
Primaire: 117Vx2 Bleu / Noir
Secondaires: 18Vx2 Bleu / Jaune
. . . . . . . . . 18Vx2 Rouge / Blanc
Ecran electro-statique: Masse Noir
One primary is wire coded Blue/White, the other primary is wire coded Blue/White
For conventional wiring to 110/120Vac one would connect the two Blue wires to Mains Live/Hot and connect the two White wires to Neutral/Cold
and
for 220/240Vac one would connect Blue of one primary to the White of the other primary. Then connect the Blue wire to Mains Live/Hot and connect the White wire to Neutral/Cold
NO !!!!!
the blue and white do not indicate the phasing of the windings. All three transformers are colour exactly the same way, so it's not a building error.
For 220/240Vac the two white wires are connected.
Then the Mains Live goes to one Blue and the Mains Neutral goes to the other Blue.
The same phasing error occurs on the secondaries.
One limb has two windings Blue/Yellow and Red/Black. Connect Yellow to Red for a series connection (in this case 36Vac) and then Blue and Black are the output.
Repeat for the other limb with it's pair of secondaries.
Now for a dual polarity supply where the windings are series connected, one needs to connect the two Black wires.
The 72Vac output is from the two Blue wires.
This is the same for all three Rcores from selectronic.
The 120VA Rcore came without any labeling. Fortunately the colour coding is identical to the 30VA
I cannot understand why the manufacturer, Shilchar, has coded the two limbs differently for phase.
I cannot understand why Selectronic does not state that one limb (both primary and secondaries) are out of phase with the other limb.
Have any of you found the same, or was the phasing correctly coded on your Selectronic/Shilchar Rcores?
Use a Mains Bulb Tester to check the primary wiring. A Variac does not prevent damage with this wire coding error.
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The regulation when checked with 234Vac applied to the series connected dual primaries is:
30VA 25.5% transformer regulation,
Primary winding resistance 152.5r
Secondary winding resistance 18.4r
120VA 15.1% transformer regulation.
Primary winding resistance 18.14r
Secondary winding resistance 2.49r
At full power the copper losses would be 6.9W for the 30VA indicating a maximum efficiency of ~81.3%
the 120VA has a maximum efficiency of ~90.4% and copper losses are 11.7W
As confirmed by another Thread, I don't know how to work out the iron losses when the transformers are delivering full power into a resistive load.
30VA 25.5% transformer regulation,
Primary winding resistance 152.5r
Secondary winding resistance 18.4r
120VA 15.1% transformer regulation.
Primary winding resistance 18.14r
Secondary winding resistance 2.49r
At full power the copper losses would be 6.9W for the 30VA indicating a maximum efficiency of ~81.3%
the 120VA has a maximum efficiency of ~90.4% and copper losses are 11.7W
As confirmed by another Thread, I don't know how to work out the iron losses when the transformers are delivering full power into a resistive load.
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The phasing conventions of transformers are wildly different dependent on the tastes and culture of the manufacturer.
Never take anything for granted.
You can measure them open circuit, using a real wattmeter (I think I showed an example of such an instrument).
For very small transformer, there will be a second order interaction between iron and copper: the magnetizing current is so high that it becomes sufficient to generate non-negligible copper losses.
You can correct the iron losses value by subtracting the Im²R from the global open circuit losses.
For large, properly designed transformers, this is not necessary
Never take anything for granted.
The iron losses are practically unchanged between zero and full load (they decrease slightly when loaded).
You can measure them open circuit, using a real wattmeter (I think I showed an example of such an instrument).
For very small transformer, there will be a second order interaction between iron and copper: the magnetizing current is so high that it becomes sufficient to generate non-negligible copper losses.
You can correct the iron losses value by subtracting the Im²R from the global open circuit losses.
For large, properly designed transformers, this is not necessary
I know that small transformers have lower efficiency and larger transformers have higher efficiency.
I know that EI and toroid have different efficiencies.
I am giving some Rcore data that may be useful to others. These are the first Rcore transformer I have had the chance to see/measure.
There was talk on another Thread that Rcore was more efficient than toroid. I asked the author for some data. He had misused the word as a result of translation, he meant something other than efficiency.
So far I have never seen comparison of Rcore to toroid transformer efficiencies.
I suspect that Rcore may have a slightly lower efficiency than Toroid, if both are designed to similar parameters/brief.
I know that EI and toroid have different efficiencies.
I am giving some Rcore data that may be useful to others. These are the first Rcore transformer I have had the chance to see/measure.
There was talk on another Thread that Rcore was more efficient than toroid. I asked the author for some data. He had misused the word as a result of translation, he meant something other than efficiency.
So far I have never seen comparison of Rcore to toroid transformer efficiencies.
I suspect that Rcore may have a slightly lower efficiency than Toroid, if both are designed to similar parameters/brief.
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Do they rate the voltage at full load?
Does that mean your getting 22.5v with no load?
Transformers are rated at full rated load.
The label on the 30VA transformer states primaries are rated @ 117Vac
Using that information I tested at that voltage.
The output without any load was 22.6Vac.
That indicates a transformer regulation of 25.5%
I can only report what I could measure.
I suspect these Shilcar manufactured transformers are being labeled incorrectly.
But I have no way to determine the real VA rating, nor the maximum operating temperature.
Selectronic have stopped selling these transformers.
I wonder why?
The label on the 30VA transformer states primaries are rated @ 117Vac
Using that information I tested at that voltage.
The output without any load was 22.6Vac.
That indicates a transformer regulation of 25.5%
I can only report what I could measure.
I suspect these Shilcar manufactured transformers are being labeled incorrectly.
But I have no way to determine the real VA rating, nor the maximum operating temperature.
Selectronic have stopped selling these transformers.
I wonder why?
i contacted one of the Chinese suppliers of r-core transformers off ebay and just got the replies today. This one i inquired on is dual 15v transformer 30VA r-core. The brand of r-core was called Zero Zone (I never used them and not vouching for them at all)
They stated ther transformer voltages were rated at a 50% load 115v in, and there 15v transformer outputs ~16.5 at no load. i believe this correlates to about a ~20% regulation assuming the regulation is linear, which, if i understand the theory right it should be. or 10% if you derated down to 15VA
This also this would mean at my local 120v - no load voltage would be closer to ~17.2v and id have to calculate off that.
But it really brings up something important. that the voltage ratings are not necessarily at 100% load, depending on the manufacturer.
Caveat Emptor - always ask or find the details of any ratings.
They stated ther transformer voltages were rated at a 50% load 115v in, and there 15v transformer outputs ~16.5 at no load. i believe this correlates to about a ~20% regulation assuming the regulation is linear, which, if i understand the theory right it should be. or 10% if you derated down to 15VA
This also this would mean at my local 120v - no load voltage would be closer to ~17.2v and id have to calculate off that.
But it really brings up something important. that the voltage ratings are not necessarily at 100% load, depending on the manufacturer.
Caveat Emptor - always ask or find the details of any ratings.
I can't see any reason to adopt a non standard VA rating method.
If they are telling you they voltage rate at 50% of the specified 30VA, then that means the voltages are when delivering only 15VA i.e. 500mAac into 60r dummy load.
I agree with your assumption that the 10% apparent regulation for the 50% duty becomes ~20% regulation when specified by the usual manufacturers' standard.
That means the transformer is a dual 13.75Vac @ 1Aac. But that is only 27.5VA. The current would have to be increased to achieve 30VA and how hot will the transformer be now?
How hot is it at 27.5VA? Why are they testing at 50% of rated VA?
Buy one if it's cheap enough and measure it.
If they are telling you they voltage rate at 50% of the specified 30VA, then that means the voltages are when delivering only 15VA i.e. 500mAac into 60r dummy load.
I agree with your assumption that the 10% apparent regulation for the 50% duty becomes ~20% regulation when specified by the usual manufacturers' standard.
That means the transformer is a dual 13.75Vac @ 1Aac. But that is only 27.5VA. The current would have to be increased to achieve 30VA and how hot will the transformer be now?
How hot is it at 27.5VA? Why are they testing at 50% of rated VA?
Buy one if it's cheap enough and measure it.
Got one on the way.
i total don't trust Chinese ebay sellers to know what there talking about unless there the manufacturer frankly.
i have a constant current load I can run it into, I'll need to rectify the output and filter it as its a dc load, but that is easy enough. i can monitor the current/voltage on the ac side and graph it.
I can probably even do a temp measurement.
once it arrives, i'll test it and post.
I've got a use for it for something totally way under spec for it. So as long as its not doing something totally weird, its not a total waste of money.
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To quote one of my favorite aussie's "She'll be right" ... 
But really, it should be...I'll be using a true RMS bench meters on the AC side so any distortion of the sinewave at the transformer output caused by the rectifier/capacitor loading will not be a problem. I'll still get correct AC rms voltages and current measurements from the output of the transformer.
so power should be equivalent, and therefor the temperature also should track identically.
Don't worry, I did not plan on using the readings off the constant current load on the DC side.
i actually did give this some thought before i decided to do it this way.
but don't get me wrong, i do agree with you, and if i was a transformer manufacturer, sure id spec it out with a restive load. It is certainly the easiest load on the transformer.
The reality is, anyone using the transformers are going to be running them into rectifiers and not purely resistive / linear loads, so its a more real world benchmark anyway.
But, the real reason i even aprached it this way is that i don't have a bunch of load resistors handy to do such a test, and don't plan on investing in any.. So the DC constant current load will have to do.
You do bring up an important point. which is using the "correct primary voltage" since these are spec'ed at 115v/230v (2 windings series or parallel wired) my line voltage here is 120 though.
So i'll run the test at spec, 115v
i could run multiple tests, just to see but i expect that once one test is run, it would be easy to calculate the results of other voltages.
But really, it should be...I'll be using a true RMS bench meters on the AC side so any distortion of the sinewave at the transformer output caused by the rectifier/capacitor loading will not be a problem. I'll still get correct AC rms voltages and current measurements from the output of the transformer.
so power should be equivalent, and therefor the temperature also should track identically.
Don't worry, I did not plan on using the readings off the constant current load on the DC side.
i actually did give this some thought before i decided to do it this way.
but don't get me wrong, i do agree with you, and if i was a transformer manufacturer, sure id spec it out with a restive load. It is certainly the easiest load on the transformer.
The reality is, anyone using the transformers are going to be running them into rectifiers and not purely resistive / linear loads, so its a more real world benchmark anyway.
But, the real reason i even aprached it this way is that i don't have a bunch of load resistors handy to do such a test, and don't plan on investing in any.. So the DC constant current load will have to do.
You do bring up an important point. which is using the "correct primary voltage" since these are spec'ed at 115v/230v (2 windings series or parallel wired) my line voltage here is 120 though.
So i'll run the test at spec, 115v
i could run multiple tests, just to see but i expect that once one test is run, it would be easy to calculate the results of other voltages.
After over 2 months - guess what showed up unexpectedly today - yes it is that Chinese r-core transformer. so much for "air mail" epacket delivery lol. 
I've long since ordered another transformer for my project as the delivery was long long overdue. , a parts-express 30va torroid transformer, and that worked out fine for me.
I can still characterize this transformer if anyone is interested. its a R25 core, Zero Zone 30VA R-core Transformer 16v-0-16v (or should be ... i've not opened the package and wouln't be surprised if its not what i ordered)
i know the usual voltages are like 15-0-15 or 18-0-18, and i've not seen this value since and see they removed it off ther list of available voltages. but at least i can see what the regulation is on the R25 series core Chinese "Zero Zone", and see what the voltages actually are compared to spec under load etc. Typicly, the regulation % is the same for any voltages within the same series of core from what I've seen from transformer specs from any manufacturer I've looked at. so I am making a somewhat reasonable assumption that would be true for the Zero Zone r-core r25 series as well.
if there is interest let me know, otherwise, i'll leave it in the box until another project comes along i can throw it into.
I've long since ordered another transformer for my project as the delivery was long long overdue.
, a parts-express 30va torroid transformer, and that worked out fine for me. I can still characterize this transformer if anyone is interested. its a R25 core, Zero Zone 30VA R-core Transformer 16v-0-16v (or should be ... i've not opened the package and wouln't be surprised if its not what i ordered
)i know the usual voltages are like 15-0-15 or 18-0-18, and i've not seen this value since and see they removed it off ther list of available voltages. but at least i can see what the regulation is on the R25 series core Chinese "Zero Zone", and see what the voltages actually are compared to spec under load etc. Typicly, the regulation % is the same for any voltages within the same series of core from what I've seen from transformer specs from any manufacturer I've looked at. so I am making a somewhat reasonable assumption that would be true for the Zero Zone r-core r25 series as well.
if there is interest let me know, otherwise, i'll leave it in the box until another project comes along i can throw it into.
Couln't help but open it up ... sure enough, they shipped me the wrong transformer, well at least i know never to do business with that eBay seller again.
i purchased a 16-0-16 v R-25 core 30VA transformer with two 115v windings which you could parellel for 115 or run in searies for 230v.
not only wasn't it 16v, what i got was a cheaper r-20 core transformer(smaller core) with two 15v windings 0-15v 0-15v and a single primary wingdings with taps for 115 and 230v
its a cheaper transformer basically.
plus the last thing i wanted was a 230v tap. I just hate the idea of that tap hanging out there when running it at 120v acting with the 230v tap acting like a 240v auto transformer.
i purchased a 16-0-16 v R-25 core 30VA transformer with two 115v windings which you could parellel for 115 or run in searies for 230v.
not only wasn't it 16v, what i got was a cheaper r-20 core transformer(smaller core) with two 15v windings 0-15v 0-15v and a single primary wingdings with taps for 115 and 230v
its a cheaper transformer basically.
plus the last thing i wanted was a 230v tap. I just hate the idea of that tap hanging out there when running it at 120v acting with the 230v tap acting like a 240v auto transformer.
does it have a centre tapped primary? i.e. 0-115-230Vac?
is the primary all on one limb?
and the secondaries all on the other limb?
The normal way to wind Ccore and Rcore is to place half the primary and half the secondary on one limb and to place the other halves of the primary + secondary on the other limb.
This gets the best coupling between the windings and also minimises the leakage flux.
Separating the primary from the secondary onto separate limbs is a bad way to manufacture an Rcore !
is the primary all on one limb?
and the secondaries all on the other limb?
The normal way to wind Ccore and Rcore is to place half the primary and half the secondary on one limb and to place the other halves of the primary + secondary on the other limb.
This gets the best coupling between the windings and also minimises the leakage flux.
Separating the primary from the secondary onto separate limbs is a bad way to manufacture an Rcore !
yes
it is hard to tell for sure, without disassembling it...as best i can tell, i see primary and secondary wires coming from both sides. like some kind of balanced configuration.
i can take pics of what i can see if your interested. what i can easily see is 1 thin primary wire going into each bobbin.. also see two thicker secondary winding going to each bobbin, obviously there should be at least one more thin wire coming from the windings and some wires going between the bobbins.. there is parts of the bobbin i cant see, also its shielded so, there could be, and likely are wires going between each bobbin.
your answer and following comments don't make any sense.
If you can see primary wiring/winding on both limbs and you can see secondary wiring/winding on both limbs then you can't have a centre tapped primary. You must have access to the 4 wires feeding the two separated primaries on the two limbs.
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