Hi!
I want som advice concerning how to best wire the mains transformer in my coming tubeamp. I need about 260 V@250 mA to the outbut tube and same voltage or maybe a little higer (se D) to the drivestage @20 mA.
In whitch case do I put the less stress to the transformer.
Regards Anders Brandt
I want som advice concerning how to best wire the mains transformer in my coming tubeamp. I need about 260 V@250 mA to the outbut tube and same voltage or maybe a little higer (se D) to the drivestage @20 mA.
In whitch case do I put the less stress to the transformer.
Regards Anders Brandt
Attachments
A will give you 0.707 X voltage with 1.414 X current.
B will give you 0.707 X current but 1.414 X voltage on each winding.
C will give you similar results to B per winding.
D must be a different transformer and a multiple of already described.
Don't forget, if the transformer is rated at 100V/A then that is all you can get, in any configuration.
None give either more or less stress on the transformer, the stress is down to smoothing capacitors and output drawn.
B will give you 0.707 X current but 1.414 X voltage on each winding.
C will give you similar results to B per winding.
D must be a different transformer and a multiple of already described.
Don't forget, if the transformer is rated at 100V/A then that is all you can get, in any configuration.
None give either more or less stress on the transformer, the stress is down to smoothing capacitors and output drawn.
A will give 30% less current than B or C for the same regulation or temperature rise. D will give two different voltages, higher one will be limited to 0.1A RMS by the smaller winding.
Thank you for fast replies. I recon that D will be the best one to choose. The trans have a third winding like in the picture. And then it's more easy smooth the voltage to the first ampstage.
Yes, 'D' will give independent supplies, with one being a bit higher voltage than the other.
However, my preference is 'C'. The reason is that the total load (current) is placed fairly across the two similar 195 VAC windings. Since P = I²R, looking at just one winding (for analysis purposes), the I is halved. Its 'R' doesn't change. Therefore the P/P = (½)² or ¼. But of course, there are 2 windings involved, so ¼ ⊕ ¼ = ½.
Still, half the power dissipation during capacitor charge cycles … is a worthy outcome.
Moreover, the 'total power' available is at the limit of the transformer without balance issues to speak of. Supposing that the pair of 195 V windings are indeed well matched to each other. co-wound equal-turn windings are the best.
Down-wind of the full-wave bridge, is filtering … and tho' it wasn't part of the discussion, 'regulation'. I highly recommend active regulation (either absolute value, or fraction-of-quiescent) via MOSFET series regulators (plural) to obtain the output, and driver voltages you desire. The technique is simple, the results better than expensive high-current chokes or large-can capacitors. It is 2020, after all!
Anyway, I apologize for the unsolicited off-topic opinion. It seemed related.
⋅-=≡ GoatGuy ✓ ≡=-⋅
However, my preference is 'C'. The reason is that the total load (current) is placed fairly across the two similar 195 VAC windings. Since P = I²R, looking at just one winding (for analysis purposes), the I is halved. Its 'R' doesn't change. Therefore the P/P = (½)² or ¼. But of course, there are 2 windings involved, so ¼ ⊕ ¼ = ½.
Still, half the power dissipation during capacitor charge cycles … is a worthy outcome.
Moreover, the 'total power' available is at the limit of the transformer without balance issues to speak of. Supposing that the pair of 195 V windings are indeed well matched to each other. co-wound equal-turn windings are the best.
Down-wind of the full-wave bridge, is filtering … and tho' it wasn't part of the discussion, 'regulation'. I highly recommend active regulation (either absolute value, or fraction-of-quiescent) via MOSFET series regulators (plural) to obtain the output, and driver voltages you desire. The technique is simple, the results better than expensive high-current chokes or large-can capacitors. It is 2020, after all!
Anyway, I apologize for the unsolicited off-topic opinion. It seemed related.
⋅-=≡ GoatGuy ✓ ≡=-⋅