The Hammond sheet uses figures in a way that shows they think about the voltage calculation a bit differently than what I'm used to (and what I think is the Old School perspective).Ray Barbee wrote: ↑Sat Feb 15, 2025 7:26 pm It was mentioned above to look at Full Wave Capacitor input, which is different than Full Wave Bridge Capacitor input, so I was pointing out that was wrong. You'll notice under the former, the hammond sheet mentions .71x total secondary.
...
What I was getting at was, in that configuration, we're looking at 1.41xtotal secondary voltage? Which is yes. That's all the answer I needed.
Most calculations in old books talk about the transformer secondary powering a non-bridge full-wave rectifier in the form "300v-0-300v" and not "600v CT."
- The Old Books (from the 1920s through 1960s) would know bridge rectifiers are uncommon because with vacuum tubes they require 3 rectifier tubes, and 3 rectifier heater windings.
- By contrast, a (non-bridge) full-wave rectifier requires only 1 rectifier tube (with 2 plates and a shared cathode/filament) and 1 rectifier heater winding.
- Since a (non-bridge) full-wave rectifier allows only half of the high-voltage secondary to conduct at any given instant, it is more convenient to calculate using the voltage of a half-winding: "300v" of the 300v-0-300v transformer.
- The Old Books don't normally describe this as "Volts x 0.5" because it's assumed the reader just knows only half the winding's AC Voltage is available for use.
Hammond apparently developed their sheet to be universal, and think about the voltage of the entire secondary winding. That likely anticipates the bridge rectifier will be more familiar to users, where the entire secondary winding is being used at all moments.
- Here, our same center-tapped transformer makes more sense to the "habitual bridge user" as "600v with a center-tap."
- The habitual-bridge-user might need reminding that a non-bridge full-wave rectifier uses only half of the total secondary winding, and that half-secondary then develops an unloaded voltage-output of 1.414x its RMS AC voltage.
- 1.414x (or call it "√2") the AC Volts of a half-winding is 1/2 the voltage that the entire secondary winding develops:
300v x √2 = 424v
600v x √2 = 848v
600v x (√2 / 2) = 600v x 0.7071 = 424v
The final bit above shows where/why Hammond uses "0.71" for a (non-bridge) full-wave rectifier: they think in terms of the "entire secondary" voltage rectifying to the peak of the AC (x √2, or x 1.414), but then dividing this factor in half because only the "half-secondary" is being used (so x√2 /2, or x0.7071, or x0.71).
The habitual (non-bridge) full-wave user thinks in terms of the half-secondary, does not multiply "300v-0-300v" by 2 to get "600v" as a starting-point, does not need a "/2" term later to convert the "peak voltage of 600v AC RMS" into the "peak voltage of 300v AC RMS" as Hammond does.
