Question about transformers, please help.

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Question about transformers, please help.
« on December 30th, 2014, 01:41 PM »
This is not a trick question or a question to catch anyone out. It is more of a fact finding exercise because there are conflicting answers depending on which Country you live in and what you believe. Below is a simple 1:2 transformer that has a pulsed dc input, a diode and a resister.
I want people to grab the picture off my thread and show me how you see it.
I want you to place a blue dot where you think the primary first see's the load impedance or energy used, place the dot on the square wave at the top.
Then show me where you think the source of power first see's the load impedance by placing a red dot on the provided square wave. Then load the picture back onto the thread and say a few words. I would be very grateful if people participated in this because it will help me design some stuff.
Thanks.

~Russ

Re: Question about transformers, please help.
« Reply #1, on December 30th, 2014, 04:37 PM »
not that i trust a simulator.  but this is what it has to say...


freethisone


nav

Re: Question about transformers, please help.
« Reply #3, on December 31st, 2014, 02:32 AM »
Could you take the picture and show me where you think the answers are please?

~Russ

Re: Question about transformers, please help.
« Reply #4, on December 31st, 2014, 07:01 AM »
Quote from nav on December 31st, 2014, 02:32 AM
Could you take the picture and show me where you think the answers are please?
i'm having a hard time understanding your question. i think the terminology is where it can get confusing., 

so the Sim has all the data in it. it shows current flow, it shows amperage, it shows voltage. that's the best i can do at the moment...

~Russ

freethisone

Re: Question about transformers, please help.
« Reply #5, on December 31st, 2014, 09:51 PM »

https://www.youtube.com/watch?v=FUUMCT7FjaI#


i too have a problem with your question..

if u first pulse a dc into the primary the magnetic flux goes up immediately until the limit is reached.

if your talking about a dot on the square wave the dot will be as soon as it is turned on, because it is a increasing magnetic flux.

so what is it exactly you want to know?

nav

Re: Question about transformers, please help.
« Reply #6, on January 1st, 2015, 03:37 AM »Last edited on January 1st, 2015, 03:50 AM
Quote from freethisone on December 31st, 2014, 09:51 PM

https://www.youtube.com/watch?v=FUUMCT7FjaI#


i too have a problem with your question..

if u first pulse a dc into the primary the magnetic flux goes up immediately until the limit is reached.

if your talking about a dot on the square wave the dot will be as soon as it is turned on, because it is a increasing magnetic flux.

so what is it exactly you want to know?
What I want to know is: We have a simple transformer with a primary and a secondary, the secondary is terminated with a resistor. The transformer is pulsed with dc voltage, the source charges the primary with voltage at V+ for a period of time. The core acts by sending current to the secondary in a magnetic field and the secondary also becomes charged with the field. Then the voltage is switching off by the signal generator. At this point both inductors on the core collapse into voltage and the resistor is presented with a potential. If the resistor is a light bulb, by now it will have lit because it can use the potential. Now, lets says that the light bulb uses all of the available inductance in the core during V- and therefore creates a load impedance value.
The source of power is still switched off remember because we are still at V-. So when does the load impedance and the source of power meet for the very first time?
I think I know the answer, they meet at the leading edge of the very next V+ pulse. That is where the transformer imparts the load impedance back to the source and the source has to pay for the power used by the resistor.

Matt Watts

Re: Question about transformers, please help.
« Reply #7, on January 1st, 2015, 12:12 PM »
Still think it would be worthwhile to really understand what is happening inside a transformer.  Remember the Chris Carson video?


https://www.youtube.com/watch?v=XsrbaCJo3Qw#

If you ever really begin to understand the medium (electricity), then knowing how to manipulate it should be far easier.

Heuristicobfuscation

Re: Question about transformers, please help.
« Reply #8, on January 1st, 2015, 07:49 PM »
Quote from nav on January 1st, 2015, 03:37 AM
What I want to know is: We have a simple transformer with a primary and a secondary, the secondary is terminated with a resistor. The transformer is pulsed with dc voltage, the source charges the primary with voltage at V+ for a period of time. The core acts by sending current to the secondary in a magnetic field and the secondary also becomes charged with the field. Then the voltage is switching off by the signal generator. At this point both inductors on the core collapse into voltage and the resistor is presented with a potential. If the resistor is a light bulb, by now it will have lit because it can use the potential. Now, lets says that the light bulb uses all of the available inductance in the core during V- and therefore creates a load impedance value.
The source of power is still switched off remember because we are still at V-. So when does the load impedance and the source of power meet for the very first time?
I think I know the answer, they meet at the leading edge of the very next V+ pulse. That is where the transformer imparts the load impedance back to the source and the source has to pay for the power used by the resistor.
monitor leading edge pulse. use feedback circuit to shut down primary.

reverandkilljoy

Re: Question about transformers, please help.
« Reply #9, on September 24th, 2015, 12:16 AM »
All of these answers are wrong....
The simulation russ gave u is nice but doesent offer any explanation...........


First off nav the source is pulse dc... Therefore impedance doesent even apply because this is not AC.... Impedance is a measure of AC reactance and inducance along with resistance..... Pulse dc is much more complicated than AC.... What happens is that when the first rising edge is applied, the current in the primary starts increasing, as its increasing the magnetic field in the core is also increasing, while this is happening a magnetic field of opposite pllairty is developing on the secondary, the rate at which this magnetic field develops on the secondary is dependant on the resistance of the secondary circuit.... So right off the get go the source sees the secondary load
Re: Question about transformers, please help.
« Reply #10, on September 24th, 2015, 04:14 AM »
Nav u misunderstand how coils work, for each edge the magnetic field in core core will charge up and then discharge once the goltage has stabilized at its V+ value, and each falling edge too....

"I think I know the answer, they meet at the leading edge of the very next V+ pulse. That is where the transformer imparts the load impedance back to the source and the source has to pay for the power used by the resistor."

Im not sure what u mean by "meet" ... How can an independant source meet with a resistance or anything.... Are u talking about phase angles ?   .... I suggest learning basic calculus so u can learn how capacitors and indictors work