PSDII

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PSDII

Postby msmpe » Wed Jun 11, 2008 11:28 pm

Hi Tubbies -

I need a critique of my procedure using PSDII. Yellow_Light_Colorz_PDT_14 I like to “verify” software before I put any faith in it besides the possibility of GIGO on my part. For this program I ran a number of published circuits to compare program results with the circuit designer’s listed B+ voltage. Circuit examples included Gizmo 6T9, Angela EL34, MA’s SE KT88, PM’s 6B4G, etc. All the circuits used Hammond PSTs and I input their listed secondary voltage say 250 for a 250-0-250VAC and let PSDII estimate winding resistance, all the rectifiers are FW, the tube is an easy pick, the filters are mostly cap input followed by LC (I used Hammond’s listed choke resistance) or RC (I used the default 2ohm cap resistance for lack of any definitive data) the R resistance is a no-brainer, and used constant current load (of course it varies but I used the design load current or close to it). I ran a long simulation to be sure all calcs leveled out. Well the results were discouraging, Yellow_Light_Colorz_PDT_21 only one was close to the circuit designer’s listed B+. The rest were inconsistent, some higher, some lower, variance from 6% to 19%. Any ideas on what I may be doing wrong??

Thanks for your help,
Nuther Nuby hooked on tubes
msmpe
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PSDII

Postby msmpe » Thu Jun 12, 2008 11:46 pm

Hi Y'all,

I decided that the current load on the PS is the variable I'm running into. I hand calculated and referred to the tube chart for the one circuit I had a definitive load current for and came up with a B+ similar to the circuit designer's (I was a percent lower, input line voltage will vary much more than thar). I then went back to PSDII and found an error in the PST voltage Yellow_Light_Colorz_PDT_09 , changed that and came up with a B+ about 5% higher than the circuit designer's.

Conclusion so far: load current is a critical variable, PSDII is a good check on hand-calcs.

Next step is to hand-design a PS, use PSDII to check, then build the circuit and measure it.

Does anybody have any "tricks or tips" when using PSDII?

NUther Nuby learning a little every day
msmpe
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Postby Ty_Bower » Fri Jun 13, 2008 6:16 am

As you have discovered, load current is critical. Equally important is the transformer source resistance. I'm often at a loss as to what number should go in there, since manufacturers don't seem to specify that value.

I generally use constant current loads in all my simulations, and avoid the resistive load. It's much easier for me to come up with a reasonably close estimate of how much current I want the circuit to draw.
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psdII

Postby msmpe » Fri Jun 13, 2008 9:23 am

Ty -

I go to the sub-dialog box and key in line and secondary voltages and just let PSDII estimate the transformer source resistance, should be based on turns ratio and current capacity or KVA to estimate amount of wire and other "EM happenings" which ultimately should be the tranny's efficiency. I have not studied trannies sufficiently to have much more knowledge than that. Yellow_Light_Colorz_PDT_11 But that data might be found in the manufacturer's spec sheet for the tranny. Lundahl has spec sheets, I could check there for a comparison. I have not seen any spec sheets for Hammond.

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