Autotransformer deep questions!
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I did an autotransformer example/derivation a while back HERE It's for an RF application but should be general enough to use elsewhere. |
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I’ll look at that, thanks!
Switching primary taps will throw off the 18VAC winding, which adds complexity to analyzing the AC Stabilizer over-all design, but that’s the way Hasan’s (photo) design has it. There’s another separate low voltage transformer that may be the same 18V, but driven from the nominal 220V (RMS, Andy!) input.
One of those low voltage windings is used as the signal source for the three threshold detected relay drivers that move the tap point, so, yeah, it’s a little obscure to analyze. One hopes it would settle into one mode without dithering when the input is near a switch point!
Dave
From: LTspice@groups.io <LTspice@groups.io> On Behalf Of
eetech00 via groups.io
Sent: Sunday, December 29, 2024 11:48 AM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Autotransformer deep questions!
Hi
Your uploaded example appears to be a transformer with a multi-tapped primary that maintains 18v output at the secondary.
I've uploaded an example "Multi_Tapped_Transformer_eT.zip"
eT |
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Just a couple or three observations: 3. I am never happy with not multiplying the RMS voltage by 1.4142 to get the peak voltage. I get why you did it that way but… Shudder.
Have fun
Suusi M-B
From: LTspice@groups.io On Behalf Of MD MUBDIUL HASAN via groups.io
Sent: 28 December 2024 16:06 To: ltspice@groups.io Subject: Re: [LTspice] Autotransformer deep questions!
I’ll update it tomorrow; getting late here. I got answers to most of my issues, so it may be a useful stating point.
>>>> Thank you very much, the schematics I showed must have some problem but its sure that autotransformer plays a vital role here. I have another design which is transformer less, lets see.
From: LTspice@groups.io <LTspice@groups.io> On Behalf Of MD MUBDIUL HASAN via groups.io
Dave Great job 👏 I will look at it.
On Thursday, December 26, 2024 at 09:41:03 PM GMT+1, Bell, Dave via groups.io <dave.bell@...> wrote:
Please see my recent upload, Autotransformer.zip
I need some tutorials regarding autotransformer modelling! I was intrigued by Hassan's AC Stabilizer and tried to model TR1 The model differed from my expectations in several ways. 1: Why do the tap-to-tap voltages differ, with equal inductances? 2: Why is the separate 18V winding so different? 2a: Why is it more different when I separate the Kxxx directives? 3: Why do the outputs throw infinities with small or megohm loads, but not when 1G or open??
Dave |
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:{) As long as the one working with the model understands that it’s not really 220VRMS, it works. In the end, it’s one constant to change, and it all works the same.
I doubt even 1 Amp is used at 18V; that load was arbitrary. Mainly, I was trying to get the turns/inductance ratios correct. Those I parameterized are close, probably close enough. (I still don’t understand all the interactions between windings, or why the inductance ratio between the nominal 220V tap and the 18V winding are close to the “correct” numbers, but not close enough.)
Dave
From: LTspice@groups.io <LTspice@groups.io>
On Behalf Of Suusi M-B via groups.io
Sent: Sunday, December 29, 2024 12:25 PM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Autotransformer deep questions!
Just a couple or three observations: 3. I am never happy with not multiplying the RMS voltage by 1.4142 to get the peak voltage. I get why you did it that way but… Shudder.
Have fun
Suusi M-B
From:
LTspice@groups.io On Behalf Of MD MUBDIUL HASAN via groups.io
I’ll update it tomorrow; getting late here. I got answers to most of my issues, so it may be a useful stating point.
>>>> Thank you very much, the schematics I showed must have some problem but its sure that autotransformer plays a vital role here. I have another design which is transformer less, lets see.
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of MD MUBDIUL HASAN via groups.io
Dave Great job 👏 I will look at it.
On Thursday, December 26, 2024 at 09:41:03 PM GMT+1, Bell, Dave via groups.io <dave.bell@...> wrote:
Please see my recent upload, Autotransformer.zip
I need some tutorials regarding autotransformer modelling! I was intrigued by Hassan's AC Stabilizer and tried to model TR1 The model differed from my expectations in several ways. 1: Why do the tap-to-tap voltages differ, with equal inductances? 2: Why is the separate 18V winding so different? 2a: Why is it more different when I separate the Kxxx directives? 3: Why do the outputs throw infinities with small or megohm loads, but not when 1G or open??
Dave
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On 29/12/2024 21:24, Suusi M-B via
groups.io wrote:
If you're talking about autotransformers with Si-iron laminate cores, then be careful with inductance measurements. John Woodgate kindly reminded me previously about relying on small-signal measurements on mains transformers. Remanence is the issue - in essence, what you measure depends on the point in the current waveform at which the circuit was last broken. It will be different each time you measure it. The only reliable method is to measure the magnetising current at the rated (primary) voltage. -- Regards,
Tony |
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That's usually the value that matters. At
lower voltages, the (calculated) inductance is normally higher,
because of the nonlinearity of the B-H curve. But the
small-signal inductance (as measured by an 'inductance meter' is
likely to be lower, for the same reason. The core permeability
is lower at very low currents. On 2024-12-29 22:02, Tony Casey wrote:
-- OOO - Own Opinions Only Best Wishes John Woodgate Keep trying |
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Jim, K7JEB
Bell, Dave
Tony Casey
John Woodgate