small correction to my post on the wire colors ... brown/brown is one secondary and gray/gray is the other secondary.
crappy way to do it, as the phase of wiring is not labeled. what they did do is solder one brown and gray together as it comes so you know how to series wire them
gawd .. well for the price... what can you expect.
crappy way to do it, as the phase of wiring is not labeled. what they did do is solder one brown and gray together as it comes so you know how to series wire them
gawd .. well for the price... what can you expect.
Zero Zone 30VA R20 core test
15V secondaries connected in series.
all readings on true RMS meters.
115v - inital power on
0.000A - 37.771V
1.000A - 30.370V
120V - run after 115v test
0.000A 39.700v
1.000A 31.965V
115V - run after 120V test
0.000A 37.509V
1.000A 30.109V
after 1 hour at 120V 1.00A load
ambient temp 32C
Core Temerature 72C (40c rise)
Coil Temerature 82C (50C rise)
120V 1.000A 30.346V
115V 1.000A 28.400V
Voltage regulation is apox. 24.5%
i'll run a longer full load test when i have time to see where the rise temperature settles out.
15V secondaries connected in series.
all readings on true RMS meters.
115v - inital power on
0.000A - 37.771V
1.000A - 30.370V
120V - run after 115v test
0.000A 39.700v
1.000A 31.965V
115V - run after 120V test
0.000A 37.509V
1.000A 30.109V
after 1 hour at 120V 1.00A load
ambient temp 32C
Core Temerature 72C (40c rise)
Coil Temerature 82C (50C rise)
120V 1.000A 30.346V
115V 1.000A 28.400V
Voltage regulation is apox. 24.5%
i'll run a longer full load test when i have time to see where the rise temperature settles out.
Last edited:
2.5 hour test at 120vac
ambient temp 25C
core temp 75C - 50C rise
coil temp 85C - 60C rise
Voltage in 120.00v
voltage out 29.680v
input power .331ma * 120.00v = 39.720VA
output power 1000ma * 29.690v = 29.690VA
Loss core and copper 10.030VA
effeciency 74.75%
i'm sure the efficiency is better when it is not hot. and like most transformers id expect the efficient to go down as the load power goes down.
i measured the resistance of the coils when hot and tried to do the copper and core loss, but, it came out with a slightly negative core loss. which means that things likely started to cool down and my resistance readings were not accurate. but it does give an indication that the core loss is very low. I don't plan on doing further testing to see exactly what the core loss is, just knowing its low is good enough for me. it just means they didn't use bad iron in the core.
I'm lead to believe the temps are reasonable as the lowest spec i could find on an r-core for max rise was 70c and most quality manufacturers were 115C or higher. so the temps seems within reason, even if you add 5C for the delta considering i was testing surface temps and conspiring the design and the length of time on, i'm doubtful that the difference is even 5C.
The efficiency was a bit disappointing. but then again the lower VA transformers are never seller performers for efficiency.
So there ya go, cheap Chinese r-core with a r-20 core.
ambient temp 25C
core temp 75C - 50C rise
coil temp 85C - 60C rise
Voltage in 120.00v
voltage out 29.680v
input power .331ma * 120.00v = 39.720VA
output power 1000ma * 29.690v = 29.690VA
Loss core and copper 10.030VA
effeciency 74.75%
i'm sure the efficiency is better when it is not hot. and like most transformers id expect the efficient to go down as the load power goes down.
i measured the resistance of the coils when hot and tried to do the copper and core loss, but, it came out with a slightly negative core loss. which means that things likely started to cool down and my resistance readings were not accurate. but it does give an indication that the core loss is very low. I don't plan on doing further testing to see exactly what the core loss is, just knowing its low is good enough for me. it just means they didn't use bad iron in the core.
I'm lead to believe the temps are reasonable as the lowest spec i could find on an r-core for max rise was 70c and most quality manufacturers were 115C or higher. so the temps seems within reason, even if you add 5C for the delta considering i was testing surface temps and conspiring the design and the length of time on, i'm doubtful that the difference is even 5C.
The efficiency was a bit disappointing. but then again the lower VA transformers are never seller performers for efficiency.
So there ya go, cheap Chinese r-core with a r-20 core.
Last edited:
so a small correction, that one Chinese manufacturer was spec'd ther 30va transformer at less then or equal to 70C rise not max, and i found another manufacturer out of china spec'd ther 30va r-core at less then or equal to 65C rise. and i can confirm that one was using an r-20 core so .. seems the temps are in line with expectations.
unless you are building an equipment intended for medical or life saving,
i can not understand why you are too concerned...
to me what is important is that your circuit gets the right amount of voltage and currents it required...
if heat is a concern, then put a lot of space around that traffo, that would have been sufficient...
do not be too meticulous about incremental differences..
i can not understand why you are too concerned...
to me what is important is that your circuit gets the right amount of voltage and currents it required...
if heat is a concern, then put a lot of space around that traffo, that would have been sufficient...
do not be too meticulous about incremental differences..
not sure if that was directed at me or not...i'm not concerned at all actually. the projects i would plan to put this in will likely pull 100ma so i'm going to be no were near 100% load.
this all steamed from the sellers on ebay not being able to give the correct specs for the transformers, and no specs other then current and voltage were posted. so i got one to test it and post the specs.
in fact i was told that the rated voltage was at 50% load by the seller... i kid you not.
anyway think the whole idea is to see if there usable or not, and it seems they are.
who is over thinking. ... hmm maybe you haven read the whole thread.
i got it specifically to test it and post the data on it as it was not otherwise available for it and then use it on a project. sadly it too 2 months for them to deliver this transformer, so i used another transformer on the project it was intended for.
i've posted the test results as promised for others to reference since the data was not otherwise available.
the transformer will sit on the shelf till its suitable for another project.
i got it specifically to test it and post the data on it as it was not otherwise available for it and then use it on a project. sadly it too 2 months for them to deliver this transformer, so i used another transformer on the project it was intended for.
i've posted the test results as promised for others to reference since the data was not otherwise available.
the transformer will sit on the shelf till its suitable for another project.
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