I don't understand the DC rating for some of the Hashimoto power transformers for full-wave center tapped rectification.
PT-150 for example, is rated at "280V-250V-220V-0-220V-250V-280V: 0.16A AC (220mA DC with Full Wave Rectifier)"
For FWCT, shouldn't the DC rating be derated 1-1.2X from the AC rating?
Another example, the PT-300B, which is specified for bridge rectifier, seems closer to my expectation as DC is derated by about 1.6.: "20V-0-280V-310V-350V: 0.53A (330mA DC with Bridge Rectifier)"
PT-150 for example, is rated at "280V-250V-220V-0-220V-250V-280V: 0.16A AC (220mA DC with Full Wave Rectifier)"
For FWCT, shouldn't the DC rating be derated 1-1.2X from the AC rating?
Another example, the PT-300B, which is specified for bridge rectifier, seems closer to my expectation as DC is derated by about 1.6.: "20V-0-280V-310V-350V: 0.53A (330mA DC with Bridge Rectifier)"
Hard to interpret the manufacturers specs, perhaps 2 eras, or perhaps 2 product engineers.
If you use a center tapped secondary, and 2 diodes in full wave, the current in each 1/2 of the secondary is on for one alternation; it is not on for the whole cycle (two alternations).
A bridge across the whole winding is on for the whole cycle (two alternations).
And, a tube rectifier's voltage drop versus current (that is resistance, even if dynamic), reduces the peak current to a cap input filter; versus solid state diodes.
However, I do know that if you use a Choke Input filter, you can always get more current out with the same thermal rise of the windings, versus using a Capacitor input filter.
True, the DC voltage only approaches 0.9 of the ACV for choke input filter;
versus the DC voltage which approaches 1.414 of the ACV for cap input filter.
If you use a center tapped secondary, and 2 diodes in full wave, the current in each 1/2 of the secondary is on for one alternation; it is not on for the whole cycle (two alternations).
A bridge across the whole winding is on for the whole cycle (two alternations).
And, a tube rectifier's voltage drop versus current (that is resistance, even if dynamic), reduces the peak current to a cap input filter; versus solid state diodes.
However, I do know that if you use a Choke Input filter, you can always get more current out with the same thermal rise of the windings, versus using a Capacitor input filter.
True, the DC voltage only approaches 0.9 of the ACV for choke input filter;
versus the DC voltage which approaches 1.414 of the ACV for cap input filter.
Right, that aligns with my thinking.
PT-150: 280V-250V-220V-0-220V-250V-280V: 0.16A AC (220mA DC)
PT-180: 280V-250V-0-250V-280V: 0.22A AC (300mA DC)
For an EL84 P-P, I assume around 175-180mA is needed for B+ winding.
If I trust the DC rating, then PT-150 should be sufficient....otherwise need the PT-180.
PT-150: 280V-250V-220V-0-220V-250V-280V: 0.16A AC (220mA DC)
PT-180: 280V-250V-0-250V-280V: 0.22A AC (300mA DC)
For an EL84 P-P, I assume around 175-180mA is needed for B+ winding.
If I trust the DC rating, then PT-150 should be sufficient....otherwise need the PT-180.
After all other tradeoffs are considered and accounted for, you will never be disappointed if the transformer runs cooler.
But I have a power transformer that never runs cooler, there just are not enough primary turns and laminations. It runs hot, because the manufacturer was cheap.
But I have a power transformer that never runs cooler, there just are not enough primary turns and laminations. It runs hot, because the manufacturer was cheap.
AC is both sides working all the time.
In the 2-diode plan, each side only works half the time.
Check for TANSTAAFL.
280V-0-280V: 0.16A AC is 560V 0.16A or 90VA of AC.
2-diode will make 396V which at 220mA is 87Watts of DC.
Plausible.