How can a transformer 2x175VAC produce 200VDC after rectifying?
It is a mystery to me.
What is the way to calculate such a Supply? Coefficient?
It is a mystery to me.
What is the way to calculate such a Supply? Coefficient?
??????
200/175 = 1.1429
How come?
I also expected 1.4142
In that case 175x1.4142 = 247VDC
But instead it is 200 ....
200/175 = 1.1429
How come?
I also expected 1.4142
In that case 175x1.4142 = 247VDC
But instead it is 200 ....
It appears that you are using Multisim. The type of probe you show does not work all that well. Use a transient simulation and collect 50 or 60 cycles. When specifying the values to display, you can input a variable that gives the waveform's RMS. This works well.
Also, remember that RMS is the "Root of Mean Square," not the average of the waveform. The 1.414 factor only applies to sinusoids.
Also, remember that RMS is the "Root of Mean Square," not the average of the waveform. The 1.414 factor only applies to sinusoids.
You are right. The values received depends on the Diode's rating.
But not even with 1000V diodes there is a correct stable value at output.
Now I get 373 Volt and then it slowly sinks. It is now 293 Volt and sinking.
Using PSU2D ( https://www.duncanamps.com/psud2/ ), and 100 ohm windings, single 1N4007 per rectifier, I get 207V output.
It is dependent on the resistance of the windings however.
It is dependent on the resistance of the windings however.
Yeah. Something like the Antek AS-1T175 has two windings of 175 V. With the two windings in parallel and loaded by 820 mA, the output voltage drops by 19 V. So that gives 19/.82 = 23 Ω for the two windings in parallel or 46 Ω for each winding. 100 Ω is probably not out of line for a smaller transformer.
You won't get exactly sqrt(2)*V_RMS at the output for a few reasons:
In reality you can expect somewhere around 1.25*V_RMS to 1.35*V_RMS with solid state rectification. Usually quite a bit less with tube rectification, though some rectifier tubes (5AR4 if I recall correctly) only drop a few volt.
I agree that seeing exact numbers in simulation on anything except a DC voltage source is pretty suspect.
Tom
You won't get exactly sqrt(2)*V_RMS at the output for a few reasons:
- Diode voltage drop
- Diode dynamic resistance IR drop
- Finite, non-zero conduction angle
- Ripple voltage
In reality you can expect somewhere around 1.25*V_RMS to 1.35*V_RMS with solid state rectification. Usually quite a bit less with tube rectification, though some rectifier tubes (5AR4 if I recall correctly) only drop a few volt.
I agree that seeing exact numbers in simulation on anything except a DC voltage source is pretty suspect.
Tom
The main filter caps charge to the peak value of the sine wave. Which is VRMS (175 VAC in your diagram) x sqrt2 or 1.414. So, approx. 247VDC in your case. Minus the rectifier diode drop, which is inconsequentially small here, minus the ripple voltage on the caps., which depends on how large in value they are, and how much load they are supplying. This usually works out to a rule-of-thumb figure of about 1.3 x VRMS. So, 175VAC x 1.3 = 227.5 VDC. There should be enough left over for the main regulator’s voltage drop.
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C1 seems to be connected only to GND, there's a small gap between output and C1 positive side.
To which of the nodes is the 200V label attached to?
To which of the nodes is the 200V label attached to?
Did you add the winding resistances in your Multisim model, or are you using the ideal model as supplied from the library?
Did you actually build this, or working in simulation only?
Did you actually build this, or working in simulation only?
Even with a 5AR5 (AKA GZ34) you get a few tens of volts drop, depending on the current. And you absolutely need some winding or series resistance in each plate/anode circuit between 50 and 125 ohms per anode/plate http://www.r-type.org/pdfs/gz34.pdf
I have a tropicalized transformer out of an old Marconi signal generator, weighing 4kg (8.8lbs). The two secondary windings are 75 ohms 300V each. That seems anomalously high, until you realize that the rectifier tubes/valves are two EY84 single rectifiers in a choke input filter and 300-0-300V, which needs a series resistance of 80 ohms per diode. So the transformer designer back in the mid 60's cunningly chose the winding wire gauge to give the resistance needed for the rectifiers http://www.r-type.org/pdfs/ey84.pdf
Note that with a capacitor input filter, the EY84 needs substantially greater series resistance
And regarding the Antek 100VA transformer. The two heater windings are 6.3V/3A each - and that is 38VA, which leaves 62VA for the HT windings. It is a hefty transformer for 100VA, suggesting that the core is running at a low B, perhaps 0.8T. That is good because it is specified to run on our Brit 50Hz, which increases the core B by a factor 60/50 = 1.2. So a core that runs at 0.8T in the US 60Hz will be pushing 1T here in blighty. It explains why most US dual standard transformers physically hum in the UK as a result of the core starting to saturate.
Craig
I'd probably contact Toroidy in Poland for a transformer for use in the UK. Shipping from Antek will be a killer.
Tom
Tom
This has been solved.
1. Use diodes with enough rating.
2. Don't use such a big capacitor.
Then it works.
I refer to the ciircuit in first post.
1. Use diodes with enough rating.
2. Don't use such a big capacitor.
Then it works.
I refer to the ciircuit in first post.
Big capacitors work. They just take longer to charge up to full voltage. However, they are better at reducing ripple.
Not sure what's going on with the diode voltage rating, though.
Not sure what's going on with the diode voltage rating, though.
Yeah - I know Toroidy. Their product looks really good. From the mass and VA they run their core quite hard, As an example, their kind of equivalent to the Antek is the 100VA TSTA 0100/003 https://sklep.toroidy.pl/en_US/p/TSTA-0100003-Mains-transformer-for-tubes/652 weighing 1.4kg (3lbs) as compared over 4lbs for the Antek.
But I know people who have bought the Supreme versions of Toroidy transformers and absolutely swear by them - but they are quite a bit more expensive than the regular versions.
Toroidy say they will wind special versions to specification, but I have no idea the cost for that.
FWIW I was in the market a couple of weeks ago for a not dissimilar specification. I ended up with an EI transformer from Primary Windings https://primarywindings.com/ this one https://primarywindings.com/product/pwht01/ . It has just the output voltages and currents I need. It is only 63VA, but weighs 1.4kg (3lbs) so the core is run at low flux density. I'm building an old piece of Racal test gear that originally specified a Gardners R106 transformer, and the PWHT01 has almost identical specification. The R106, from the 60's was more of a beast at 4.5lbs, but that was before grain oriented steels, and used thicker lams, which increases core losses.
Craig