Am I missing something?
The noratel 50VA can deliver 2A on its secondary. This means if it's a 25V output on the primary 230V you will see something around 200mA.
The noratel 50VA can deliver 2A on its secondary. This means if it's a 25V output on the primary 230V you will see something around 200mA.
i have to correct me:
this noratel is a 115V 2x primary version.
so for e.g. US you can parallel the windings- therefore 2A.
thx
chris
this noratel is a 115V 2x primary version.
so for e.g. US you can parallel the windings- therefore 2A.
thx
chris
no!
i have to correct my self: i mixed secondary and primary in post 320
thx
this transformer is a 2x secondary and 2x primary.
if you are in a country with e.g. 230/240VAC then you have to connect the primary in series. the the windings are prepared for 230VAC primary.
if you are in a country with 115VAC the you have to use this windings in parallel.
each secondary:
15VAC with 1,67Amp is 25VA
link to the transfomer
i have to correct my self: i mixed secondary and primary in post 320
thx
this transformer is a 2x secondary and 2x primary.
if you are in a country with e.g. 230/240VAC then you have to connect the primary in series. the the windings are prepared for 230VAC primary.
if you are in a country with 115VAC the you have to use this windings in parallel.
each secondary:
15VAC with 1,67Amp is 25VA
link to the transfomer
Attachments
Ok so my nbrs are correct.
You only draw 200mA from the 230V net and on netgrid of 115V it will be around 400mA through the primaries.
You only draw 200mA from the 230V net and on netgrid of 115V it will be around 400mA through the primaries.
These are the maximum values of the transformer when your secondary windings request this power.
I am not Sure which current we have with all modification.
Roughly i guess...
For Input Stage ips 1 mA
For VAS 4 mA
For Output Stage OPS 10 mA
So we have about 15 mA per rail.
Roughly i guess...
For Input Stage ips 1 mA
For VAS 4 mA
For Output Stage OPS 10 mA
So we have about 15 mA per rail.
I know. But you were talking about the fuse needed and the primary current in post #320.
You mentioned the primary current is 2A but the EMF filter is just 1A so you need a 1A fuse.
That's confusing me.
If the secondary current is 1/10 to the primary.
To make the fuse blow at 1A then you will have 10A in your secondary.
I guess your circuit is already long gone before it reaches that level.
You mentioned the primary current is 2A but the EMF filter is just 1A so you need a 1A fuse.
That's confusing me.
If the secondary current is 1/10 to the primary.
To make the fuse blow at 1A then you will have 10A in your secondary.
I guess your circuit is already long gone before it reaches that level.
I think you should use different "calculations" depending on the design and consider inrush current.
A power amp with high inrush current should be approached differently from a low powered pre-amp without no inrush current.
Also the type of fuse used... Slow blow or fast blow is something to consider.
630mA looks ok for 50VA use, but how much does the circuit actually use?
From Sherman's calculation 2 times 15mA, with 15V gives 450mW.
With some headroom thats let s say 1VA.
1VA is something else the 50VA of the transformer used.
A 630mA fuse in the primary will blow if you have 6A secundary.
I would go for something around 40mA.
A power amp with high inrush current should be approached differently from a low powered pre-amp without no inrush current.
Also the type of fuse used... Slow blow or fast blow is something to consider.
630mA looks ok for 50VA use, but how much does the circuit actually use?
From Sherman's calculation 2 times 15mA, with 15V gives 450mW.
With some headroom thats let s say 1VA.
1VA is something else the 50VA of the transformer used.
A 630mA fuse in the primary will blow if you have 6A secundary.
I would go for something around 40mA.
i made a mistake...i wrote wrong.
primary you need less current... because of the 230V
secondary we nee just 100mA or less fuse.
If the secondary current is 1/10 to the primary.
no
it depends on the ratio of the transformer.
primary you need less current... because of the 230V
secondary we nee just 100mA or less fuse.
If the secondary current is 1/10 to the primary.
no
it depends on the ratio of the transformer.
Hmmmh...
until yet i had no trouble with this calculation. I use this with transformers smaller 100 VA, i forget to write.
630mA T, t=time delay, slow blow i think. In German "träge"...
Cherman's, Chris, transformator is much too big. My transformer too...i take what i have in stock...My Transformer has secondary 2 x 1 A, 30VA, so i use
315 mA T primary fuse.
I think Elektor has a similar calculation. The Supra 2, my last project from Elektor, has build in an 6 VA transformator. With my calculate 52... mA, they use 100 mA T primary fuse, i had choosen too...
This Calculator hhttps://goodcalculators.com/transformer-calculator/ is more precise, i hope
Peter
until yet i had no trouble with this calculation. I use this with transformers smaller 100 VA, i forget to write.
630mA T, t=time delay, slow blow i think. In German "träge"...
Cherman's, Chris, transformator is much too big. My transformer too...i take what i have in stock...My Transformer has secondary 2 x 1 A, 30VA, so i use
315 mA T primary fuse.
I think Elektor has a similar calculation. The Supra 2, my last project from Elektor, has build in an 6 VA transformator. With my calculate 52... mA, they use 100 mA T primary fuse, i had choosen too...
This Calculator hhttps://goodcalculators.com/transformer-calculator/ is more precise, i hope
Peter
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yes i know it is a way too big.
.....its for a bigger Pre project like BA-3 or similar.
the current for a fuse for each transformer is the maximum rating without damage the transformer.
so to use a little fuse -less current is not a fault.
chris
.....its for a bigger Pre project like BA-3 or similar.
the current for a fuse for each transformer is the maximum rating without damage the transformer.
so to use a little fuse -less current is not a fault.
chris
Fantastic. Cheers.
I bought one of those Aliexpress boards to tinker with.
I'm in deeper with your SPICE file.
Thanks
I bought one of those Aliexpress boards to tinker with.
I'm in deeper with your SPICE file.
Thanks
Correct. The ratio from the transformer determine the voltage and current ratio.
If you put more electronics in one box is it not better to individually fuse them?
Yes it is always goo to use fuses.
a transformer has 3 fuses.
in the datasheet you see that fuse
for an power amp e.g. APEX FX8 is a rail fuse installed too.
it is on the person who is "designing" the box....if you are a fearless amp builder FAB then you don´t care about dimension with some margin and try out with no safety things like SSR or DC protection.
chris
a transformer has 3 fuses.
- primary fuse to safe the wire on the primary windings
- secondary fuse for the caps or load which can draw too much or a defect diode array or whatever
- thermal fuse which is in between the windings - about 45-50°C
in the datasheet you see that fuse
for an power amp e.g. APEX FX8 is a rail fuse installed too.
it is on the person who is "designing" the box....if you are a fearless amp builder FAB then you don´t care about dimension with some margin and try out with no safety things like SSR or DC protection.
chris
