Re: Linear Transformer Model Which Can Also Simulate its LPF Function
On Wed, Jul 5, 2023 at 02:30 PM, Donald H Locker wrote:
I understand that, but the resonant winding is not visible to users. Ferroresonant xformers appear to be two-winding devices for all practical purposes.
Yes, this is a practical solution in many applications. In fact, my first thought was to look if there is a hidden third resonant winding. But I found out that the inverter transformer is indeed a normal one, though it has two bobbins instead of one which is usually used to reduce the flux leakage.
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
On Wed, Jul 5, 2023 at 03:59 PM, Jerry Lee Marcel wrote:
Just like the nominal inductance largely varies between 50Hz and 16kHz, so does the leakage. The magnetic permeability decreases significantly at HF, so te fraction that goes through the air becomes proportionally higher.
So, you mean that the impedance Z of the leakage inductance, is somehow proportional to F^2 (since Z=wL is proportional to F already). For instance, to allow some flux leakage to exist, the transformer should have 2 separate bobbins, not one. ?
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
Just like the nominal inductance largely varies between 50Hz and 16kHz, so does the leakage. The magnetic permeability decreases significantly at HF, so te fraction that goes through the air becomes proportionally higher.
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
You may insist, but the? OP gives contrary evidence:
"pure sinewave inverters which use conventional two-winding iron core transformers. Their transformer is driven by a MOSFET bridge"... " driven by a sinewave PWM"
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
It seems all here agreed that the other element in LPF is Rpar(hi) which represent the various core losses at the PWM high frequency.
Now I have to find out a rather simple practical test to measure, even approximately, this Rpar(hi) of the unknown cores that the local retailers offer.
For instance, aren't the leakage inductances independent of frequency (at least for this application), so that they can be measured simply at 50 Hz?.
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
Rpar = R(af+bf^2) near enough,
for suitable values or R, a and b. You need data on the core
material to determine them. af is eddy-current loss and bf^2
is hysteresis loss.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-05 12:25, Tony Casey wrote:
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On 05/07/2023 13:06, Kerim via groups.io wrote:
Now the question
is how we can translate this to an equivalent circuit.
None of the actual various equivalent circuits of a transformer
seems being able to simulate its function as a stand-alone LPF!
Are you adding a shunt resistance (Rpar) to simulate core loss?
--
Regards,
Tony
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
I understand that, but the resonant winding is not visible to
users. Ferroresonant xformers appear to be two-winding devices for
all practical purposes.
Donald.
On 2023-07-05 05:09, Jerry Lee Marcel
wrote:
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Le 05/07/2023 à 10:58, Donald H
Locker via groups.io a écrit?:
Sounds like a ferroresonant power conditioner. Does that ring
a bell? I don't think they are very efficient, but they are
quite effective at producing sine waves from all kinds of
nasty inputs.
OP specified "pure sinewave inverters which use conventional two-winding
iron core transformers."
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
On 05/07/2023 13:06, Kerim via groups.io wrote:
Now the question is
how we can translate this to an equivalent circuit.
None of the actual various equivalent circuits of a transformer
seems being able to simulate its function as a stand-alone LPF!
Are you adding a shunt resistance (Rpar) to simulate core loss?
--
Regards,
Tony
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
Losses as a resistor in parallels with the winding and less
significantly paraitic capacitance.
Remember that losses increase largely with frequency, so harmonics
and switching residuals are attenuated more than the fundamental.
The basic linear model cannot represent that accurately. You have
to consider one value of Rloss for fundamental, and other values
for harmonivs and residuals.
Le 05/07/2023 à 13:06, Kerim via
groups.io a écrit?:
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On Wed, Jul 5, 2023 at 01:45 PM, Alan Pearce wrote:
Don't forget that the iron core will have losses at
the switching frequency, along with the inductance of the
windings which will have a significant impedance to the high
frequency switching. These will all have an affect on the output
waveform, forcing it to be more sinusoidal.
Now the question is how we can translate this to an equivalent
circuit.
None of the actual various equivalent circuits of a transformer
seems being able to simulate its function as a stand-alone LPF!
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
On Wed, Jul 5, 2023 at 01:45 PM, Alan Pearce wrote:
Don't forget that the iron core will have losses at the switching frequency, along with the inductance of the windings which will have a significant impedance to the high frequency switching. These will all have an affect on the output waveform, forcing it to be more sinusoidal.
Now the question is how we can translate this to an equivalent circuit. None of the actual various equivalent circuits of a transformer seems being able to simulate its function as a stand-alone LPF!
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
Don't forget that the iron core will have losses at the switching frequency, along with the inductance of the windings which will have a significant impedance to the high frequency switching. These will all have an affect on the output waveform, forcing it to be more sinusoidal.
On Wed, Jul 5, 2023 at 01:04 PM, Jerry Lee Marcel wrote:
That's because the leakage inductance is rather high.
So, in your opinion, what could be the other element in the transformer to complete its LPF response since there is no load at its HV output?
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
On Wed, Jul 5, 2023 at 01:04 PM, Jerry Lee Marcel wrote:
That's because the leakage inductance is rather high.
So, in your opinion, what could be the other element in the transformer to complete its LPF response since there is no load at its HV output?
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
That's because the leakage inductance is rather high.
Le 05/07/2023 à 11:33, Kerim via
groups.io a écrit?:
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On Wed, Jul 5, 2023 at 11:48 AM, John Woodgate wrote:
The 'other element'
is mostly the load resistance reflected into the primary
circuit.
Your answer is
logical.
But I was surprised when I
tested a ready-made inverter, its HV output (of a
conventional iron core transformer) was sinewave even
without a capacitor as a load!
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
On Wed, Jul 5, 2023 at 11:48 AM, John Woodgate wrote:
The 'other element' is mostly the load resistance reflected into the primary circuit.
Your answer is logical.
But I was surprised when I tested a ready-made inverter, its HV output (of a conventional iron core transformer) was sinewave even without a capacitor as a load!
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
Le 05/07/2023 à 10:58, Donald H Locker
via groups.io a écrit?:
Sounds like a ferroresonant power conditioner. Does that ring a
bell? I don't think they are very efficient, but they are quite
effective at producing sine waves from all kinds of nasty
inputs.
OP specified "pure sinewave inverters which use conventional two-winding
iron core transformers."
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
Sounds like a ferroresonant power conditioner. Does that ring a
bell? I don't think they are very efficient, but they are quite
effective at producing sine waves from all kinds of nasty inputs.
Donald.
On 2023-07-05 04:00, Kerim via
groups.io wrote:
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I guess many of
you, if not all, heard of pure sinewave inverters which use
conventional two-winding iron core transformers.
Their transformer
is driven by a MOSFET bridge which, in turn, is driven by a
sinewave PWM (for 60/50 Hz) whose frequency could be 16 KHz, for
example.
This means that
the transformer, with or without load, can also act as an
effective low pass filter (perhaps with a very small ripple on
its output voltage).
?
My first thought
is that the transformer’s leakage inductances play the main
element(s) in its function as LPF. But there must be another
element to complete the LPF. Is it the stray capacitances, the
core losses or both?
?
In vain, I have
searched a linear model which could be used in simulating a
transformer in such application.
I wonder if
someone recalls that such a model could exist in the group’s
archive so that I will redo my search looking for it.
?
Thank you.
Kerim
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
The leakage inductance, in conjunction with the resistive part of the load, constitutes a 1st-order LPF. The stray capacitances are in most cases negligible in this respect.
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Re: Linear Transformer Model Which Can Also Simulate its LPF Function
The 'other element' is mostly
the load resistance reflected into the primary circuit.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-05 09:00, Kerim via
groups.io wrote:
toggle quoted message
Show quoted text
I guess many of
you, if not all, heard of pure sinewave inverters which use
conventional two-winding iron core transformers.
Their transformer
is driven by a MOSFET bridge which, in turn, is driven by a
sinewave PWM (for 60/50 Hz) whose frequency could be 16 KHz, for
example.
This means that
the transformer, with or without load, can also act as an
effective low pass filter (perhaps with a very small ripple on
its output voltage).
?
My first thought
is that the transformer’s leakage inductances play the main
element(s) in its function as LPF. But there must be another
element to complete the LPF. Is it the stray capacitances, the
core losses or both?
?
In vain, I have
searched a linear model which could be used in simulating a
transformer in such application.
I wonder if
someone recalls that such a model could exist in the group’s
archive so that I will redo my search looking for it.
?
Thank you.
Kerim
|
Linear Transformer Model Which Can Also Simulate its LPF Function
I guess many of you, if not all, heard of pure sinewave inverters which use conventional two-winding iron core transformers.
Their transformer is driven by a MOSFET bridge which, in turn, is driven by a sinewave PWM (for 60/50 Hz) whose frequency could be 16 KHz, for example.
This means that the transformer, with or without load, can also act as an effective low pass filter (perhaps with a very small ripple on its output voltage).
?
My first thought is that the transformer’s leakage inductances play the main element(s) in its function as LPF. But there must be another element to complete the LPF. Is it the stray capacitances, the core losses or both?
?
In vain, I have searched a linear model which could be used in simulating a transformer in such application.
I wonder if someone recalls that such a model could exist in the group’s archive so that I will redo my search looking for it.
?
Thank you.
Kerim
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Re: No MAX31740 Spice Model
Hello !
Does this suit you ?
/g/LTspice/files/Temp/MAX31740.zip
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John Woodgate
Tony Casey