PT's (loaded vs unloaded ratings)

[passfan]

So I'm seeing references about a "loaded" rating on the Edcor power transformers for the first time and I'd like to be straight on what it means to my calculations. Do I normally calculate the DC conversion at 1.4 (approximate) and look at that figure as a loaded , aint going to drop any more, figure ? What exactly does this "loaded" term mean ?

[FYL]

PT's windings show a substantial DC resistance, which drops voltage when current is drawn.

Try Duncan's PSUD2
http://www.duncanamps.com/psud2/index.html

[Jana]

The loaded rating means the voltage will be less if you have been drinking.

It could also mean that a transformer rated at 300-0-300 @ 150ma. will provide that 300-0-300 when 150ma. is being drawn. But, that is the technical side of things--I like the first definition better.

[rfgordon]

I just finished a build with an Edcor PT (and OT). It is definitely a strong beast. I'd say that you need to know pretty closely what your current draw is going to be at idle and spec/choose the PT accordingly.

The Edcors run strong and cool. The PT sounds great, too.

[Firestorm]

Most transformer ratings seem to assume a purely resistive load rather than diodes and caps, so rated voltage is typically quite an overstatement.
A 300-0-300, 300mA PT will typically produce a B+ of 400VDC or less with silicon rectifiers, 60uF filter and only 100mA flowing. Regulation percentage also varies quite a bit model to model and brand to brand. You almost have to measure and see what you get.

[passfan]

Yes I understand a transformer will drop voltage as load is applied but it seems they are saying that at this pt's current rating it will drop no lower than 300-0-300. which if I calculate out would be 420 volts DC for B+ with the tubes in. Is this a correct rough calculation ?
I also make it a point to never let my pt's drink before or during a gig, and never on sundays.
Is duncans psud2 going to compensate for an Edcor rated PT ?

[FYL]

Is duncans psud2 going to compensate for an Edcor rated PT ?

???

Just measure the voltages and DCR of the primary and secondary windings, plug the values in Psud2 an get your sim rolling.

[passfan]

Okay, sorry for the mental lapse. I guess Edcor giving their windings with the rating loaded threw me for a loop.

[passfan]

Is duncans psud2 going to compensate for an Edcor rated PT ?

???

Just measure the voltages and DCR of the primary and secondary windings, plug the values in Psud2 an get your sim rolling.

What type of load should I use for a sim ?

[FYL]

What type of load should I use for a sim ?

Either a current sink or a resistor. Check the online help.

[passfan]

What does "a current sink has pulled the voltage below 0 for more then 5 mains cycles at 0.08...." mean? Is this a bad thing or should I overlook it? This flashes up when I simulate my rocket power supply in psud II.

[VacuumVoodoo]

Put time delay into current sink. You need to give the caps in the ripple filter enough time to charge up to full voltage before you begin to suck current out them.

[passfan]

Put time delay into current sink. You need to give the caps in the ripple filter enough time to charge up to full voltage before you begin to suck current out them.

Well I'm not as adept with the design end of building amps as I am with following instructions. Could you dumb that down for me ? How do I add a time delay. I understand what your telling me I just don't know how to change it.

[VacuumVoodoo]

Double click on current sink symbol in the schematic
There are two flavours of current sink available. The first remains static throughout the simulation, the second allows the current to change at a predetermined time.
Stepped load: Check this box if you want to use a current sink which changes during the simulation.
Value1: This must always be filled in - it's the current which will be used for the start of the simulation, or all of the simulation if the stepped load box has not been checked. "1m" is a good start value
Value2: Only filled in if a stepped load is being used - this is the current value which will be adopted after a predetermined time. That is whatever your final current draw is, 100m or 500m
After: type in number of seconds you want before the sink switches from Value 1 to Value 2
Click "OK"

Do this for every current sink in the schematic, yes you can have several.