Psud2 Help

[soundbadger]

i am trying to design a power supply using psud2.
however to model the supply i need to know the transformers secondary resistance,,,
however most manufacturers dont state this on their specs,
how can i get round this, or is a case of buying a transformer, measuring the restance and then working from there.
cheers
soundbadger

oh and just to let you know the transformer i was looking at was the hammond 300bx so if anyone knows the secondary resistance of this tx or has one that they could measure it would be very usefull

[AndrewT]

you can insert some of the known parameters of the transformer and PSUD2 may be able to estimate from them.

[soundbadger]

could you explain how?

[AndrewT]

click on the transformer symbol.
dialogue box comes up
enter values in the two fields or click on the right hand options
new dialogue boxes come up
enter your known data and see if it completes the blank fields with sensible values.

[Sheldon]

Originally posted by soundbadger
could you explain how?

You really only need four measurements: Measure the DC resistance of the primary and secondary (full winding for a center tapped secondary). Connect the primary to line power and measure the line voltage and the unloaded voltage at the secondary.

Right click on the transformer symbol for the dialog box. Click on the "Ohms" button. A new dialog box will come up. Enter your supply (line) voltage, primary winding resistance, secondary voltage, and secondary winding resistance. It will calculate the transformer parameters for you and will plug them into your supply model when you select OK. Record your measurements, because you will have to re-enter them all if you want to edit this calculation.

Sheldon

[Robert McLean]

All I would do is enter 5% for the regulation, and let PSUD calculate the rest. If and when you get a transformer do the resistance measurements, and plug them in. You will have to know the nominal voltage and the rated current for the transformer. The hammond website lists the rated DC current out of the attached rectifier, you will have to coinvert that to AC current for PSUD by dividing by 1.54.

Depending on if the regulation really was 5% or not, you may end up with a no load voltage difference of 10 or 20 volts. So what, 20 volts here or there in plate supply is nothing.

If your design draws a current near to the rated current of the transformer then regulation wont matter anyway, your transformer will be putting out the nominal voltage, and PSUD and your circuit should match exactly. (in theory)