Some troubles with PSUD. A little help please !

[Antonio Tucci]

I'd like to understand why the simulation with PSUD does not produce the same values reported in the schematics.
For example ...
if I utilize the values reported in the power supply of the
300B stage of the schematic reported below (*)... I do not obtain the same value of V with PSUD.
Specifically, I obtain more than 500 Vrms after the 160 uF capacitor, with PSUD... instead of the 385 reported on the original schematic.

This aspect recurs also with other schematics. Why ?

The only variable thing I include into the simulation is the constant current load that I utilize (at the end of the filter) to test the
circuit ... and that corresponds to the current circulating into the circuit (i.e. 85-90 mA in the case of the schematic reported below).
Is it correct ? ... or I have to utilize a R load ? ... and if so ... which values to choice ?

Many thanks

Antonio Tucci

(*) http://home.att.net/~chimeraone/axiom300bschematic.html

[SY]

Just a guess, but I'll bet you're not using the right value for the transformer source resistance. It should be (roughly) DCR of the secondary plus the turns ratio times the DCR of the primary.

[poobah]

A current source (actually a "sink") is appropriate to use here.

Have you included the resistance of your chokes in the model?

Also, be certain to adjust your "reporting" time. People often (me too) look at the start up behavior by mistake...

[Antonio Tucci]

The DCR of inductors is already reported into the original schematic... and I utilize those values.

As to the time For ... I usually select 10.000 ms, with a delay of 0 sec.

[poobah]

OK then....

Set your period to one second, after 10 seconds delay. You are looking at start-up transients.

[Sheldon]

Originally posted by SY
Just a guess, but I'll bet you're not using the right value for the transformer source resistance. It should be (roughly) DCR of the secondary plus the turns ratio times the DCR of the primary.

PSUD will calculate this if you click on the Ohms tab in the Edit box for transformer properties. Still need to enter measurements of primary and secondary resistance and input and output voltages.

Sheldon

[Zen Mod]

Originally posted by Sheldon


PSUD will calculate this if you click on the Ohms tab in the Edit box for transformer properties. Still need to enter measurements of primary and secondary resistance and input and output voltages.

Sheldon

agree;
this must be culprit
I always find that PSUD is good no less than imported values

[Tweeker]

I do think start up transients and load steppings are a good thing to look it. Lots of ringing is not good and could make for instability.

[Antonio Tucci]

poobha

OK then....

Set your period to one second, after 10 seconds delay. You are looking at start-up transients.

Also with those setups ... the results do not change.
I have discovered that eliminating the "stepped" option from the load current box ... the Vrms value decreases from > 500V to 363-369 Vrms (according to the DCR value of the secondary of the main transformer ... 31 or 110 ohm).
However, these values are still far fom the 385 V.

[poobah]

I need to check out the "stepped option"... you are within 20 volts... that's pretty good.

EDIT... yes stepped load should be OFF.