Hello all,
Thanks in advance for being here. Last time I gained what I feel is a good basic understanding of cores. Thanks again to DickChappels.
This time I really could use some help getting a better understanding of well... When I see a basic transformer. One primary. One secondary. No tap.
The top coil for lack of a better term is "tuned" to how much force it will put on the secondary. factored by turns and gage of wire. I understand that if I plug in AC power to this coil that someone else made. One that is already correct in its application. the secondary coil will also put out an ac voltage. That voltage will pretty much be as expected based on math. Heres where im almost regressing I feel. What else can I plug in to the primary? DC? I'm getting information pertaining to alternating square waves to drive this older mini-neon lcd Transformer. It is one a lot like this

Pretty sure it was a Great Scott video. He took out the primary. Wound a new one. Four turns. .85 Ga.. Ok well he
did say it was a square wave "inverter" so my guess. His input, no different then simply using a cheap store bought
inverter? Square wave AC. Nothing more. A PWM signal however. Square wave right? Just does not go into the negative
range of voltage yes? If at the point it did dip down into the negative voltage. Would no longer be a DC PWM signal.
At that point you would have Square wave AC. I hope I am right but I dont know? I know I did try to input 12VAC 1 amp
to the four turns I mentioned and when I applied the voltage It seemed nothing happened on the secondary side. Could not
detect voltage. So In my experiment I am aware that my input was not the same as his. However I do not understand why
It would not work or should it? I grabbed the link to the video as well. For anyone that wants to check it out.

 

Because it's an inverter transformer and designed for Higher Frequencies like 80-140Khz, so it wont be any use on 50/60Hz, also the material is ferrite not soft iron laminate.

 

Heres where im almost regressing I feel. What else can I plug in to the primary? DC? I'm getting information pertaining to alternating square waves to drive this older mini-neon lcd Transformer. It is one a lot like this

Yes, per Dodgydave, the transformer shown will pass high frequency AC waveforms.

Pretty sure it was a Great Scott video. He took out the primary. Wound a new one. Four turns. .85 Ga.. Ok well he
did say it was a square wave "inverter" so my guess. His input, no different then simply using a cheap store bought
inverter?

Inverters and transformers are designed to work together as a system. One might get lucky and get the transformer to work well with a cheap store bought inverter, but it is unlikely. Many factors that vary from circuit-to-circuit affect compatibility, for example primary and secondary voltages and currents, mode of operation (buck, boost and variations), frequency, whether or not DC is present in the primary...)

Square wave AC. Nothing more. A PWM signal however. Square wave right?

Sometimes it is a simple square wave but other waveforms are used and they are modulated in various ways including but not limited to PWM.

Just does not go into the negative range of voltage yes? If at the point it did dip down into the negative voltage. Would no longer be a DC PWM signal. At that point you would have Square wave AC. I hope I am right but I dont know?


I know I did try to input 12VAC 1 amp to the four turns I mentioned and when I applied the voltage It seemed nothing happened on the secondary side. Could not detect voltage. So In my experiment I am aware that my input was not the same as his. However I do not understand why It would not work or should it? I grabbed the link to the video as well.

Yes the signal on the secondary will be AC. A square wave that goes from 0 to 10 volts on the primary would swing positive and negative on the secondary.

 

@jgreene44 Pulsating DC is not the same as a AC.
A DC derived square wave pulse imposed on the primary is not necessarily AC, there are circuits that will actually reverse the polarity on the primary in order for the true AC to be imposed.
Max.

 

Dick! glad you returned. truly. Ok you verified a lot for me. You also raised a question/point or two.

Ok this:

↑
Heres where im almost regressing I feel. What else can I plug in to the primary? DC? I'm getting information pertaining to alternating square waves to drive this older mini-neon lcd Transformer. It is one a lot like this
Yes, per Dodgydave, the transformer shown will pass high frequency AC waveforms.

I understand He and you are saying the secondary will produce a high freq. waveform at the output. However.

My assumption is this:

One ferite rod
two coils wrapped around it
any reasonable guage
input a sinusoidal waveform
any freq
any amplitude
to one of the coils

Something should happen on the second coil? Now what I am wondering is. Am I mistaken? Can there be mismatches that produce zero output on the secondary? As in this example. Is this why i see nothing at the output? If I had the answer to this I think I would be solid on that part of understanding transformers.

I defiantly want to add this as well. You stated that a square wave... say 0-20VDC. Im understanding much like a pwm signal or is a pwm signal. will induce a sinusoidal output on the secondary. Neat! That would have evaded me if not for that information. My understanding this far was it had to be sinusoidal. My understanding of sinusoidal is yes a waveform but also one that centers at 0 amplitude. Is this wrong as well? Can a pwm signal be considered sinusoidal? it is an oscillation? perhaps Its some kind of pixie magic that happens during induction. Ill be wicked interested in the answer either way!

Doing some further reading now that my wheels are turning. and ya much like this I always see the wave form centered at 0 amplitude. Is this misleading?

 

Max. I am sorry if it appears that I payed no attention to what you said. Your comment did not appear until
after I responded. I do however hear you load and clear. I am also understanding even without this change via circuitry that it would still output AC on the secondary based on dickchappels comment. correct any mistake thank you.

 

A transformer (within its frequency limitations) will transform a change in voltage on the primary to a change in voltage at the secondary, as determined by the turns ratio, whether it is sine or square or anywhere in-between.
It does not, by itself, convert a square-wave to a sinewave.
Ideally there is no change is waveshape between the primary and secondary.

A PWM signal will also appear as PWM at the secondary but may be significantly filtered due to the transformer frequency response limits.
For example, sine-wave 50-60Hz power inverters generate a PWM signal modulated with a 50-60Hz sine-wave at the primary which is filtered at the transformer secondary to give a sinewave output.

Of course a transformer cannot transform DC from the primary to secondary.
All DC does in generate a DC current in the primary which can saturate the core and kill any transformer action to AC.
If the circuit driving the transformer has a DC component, such as a unipolar pulse train or square-wave, the signal can be coupled through a capacitor to block the DC.
A transformer can be designed to handle small amounts of DC current without saturating, if required.

 

Great information sir. Is it now safe to assume:

If the primary and secondary are too far out of spec. The primary would fail to induce voltage on the secondary?

My input to the said transformer:
20VAC
50Khz would be my assumption (is it khz, Khz? I always mess that up. both right?)
4 winds .85 ga.
No reading at the output.

If this input failed to induce. I wonder what it would take to change that?

This I need to address also:

Yes the signal on the secondary will be AC. A square wave that goes from 0 to 10 volts on the primary would swing positive and negative on the secondary.

Dick stated this and it sort of has me thinking ok was 0 to 10. Now its Swinging negative on the output. You stated the waveform is even filtered some. In the oscilloscope in my mind. (the one I wish I had lol) We have sinusoidal AC? Or real close to it. Ya further advice appreciated

 

My input to the said transformer:
20VAC
50Khz would be my assumption (is it khz, Khz? I always mess that up. both right?)
4 winds .85 ga.
No reading at the output.

Try more turns on the primary.

Yes the signal on the secondary will be AC. A square wave that goes from 0 to 10 volts on the primary would swing positive and negative on the secondary.

Dick stated this and it sort of has me thinking ok was 0 to 10. Now its Swinging negative on the output. You stated the waveform is even filtered some. In the oscilloscope in my mind. (the one I wish I had lol) We have sinusoidal AC? Or real close to it. Ya further advice appreciated

It will be filtered some, but that generally will only round off the edges of the square-wave and perhaps add some droop to the flat portions of the wave, not enough to convert it to a sine-wave.