Saturation Current of a Transformer

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Saturation Current of a Transformer

Рет қаралды 16,356

5 жыл бұрын

This is a short video showing a circuit used to find the saturation current of a transformer. I show that voltage is applied, the current rises linearly with time. Howver there is a point where the core can not produce anymore flux and instead of the transformer showing an inductance, it shows the characteristic of a wire. The saturation of the core material should always be avoided and is an undesired condition. Questions, and comments can be sent to rbola35618@aol.com. If you find the video useful, please subscribe, like and share.

Пікірлер: 57

@UpcycleElectronics 5 жыл бұрын

Thanks. This was the most practical demonstration I've seen. I need to build this rig and try it myself. Much appreciated. -Jake

@RobertBolanos 5 жыл бұрын

Thank you

@gibbyrockerhunter 10 ай бұрын

Man I am really loving your explanations. Thanks for all of the content

@chevylization 3 жыл бұрын

Thanks a lot Robert. Just what I was looking for, this method is great. I was looking for a way to determine the minimum safe operating frequency for a transformer. Just have one transformer and thoughts about saturation was haunting me. I just used an IGBT in the need for a MOSFET of that capacity and worked like a charm. Good to know there are still real engineers left.

@RobertBolanos 3 жыл бұрын

Thanks for the kinds words. You made my day.

@glennkirilow9015 2 жыл бұрын

This is incredible content Robert, I'm going to pass this onto my network, I'm sure we will all learn so much from you. Thanks so much for taking the time to do this, it's an important mission. - Glenn

@RobertBolanos 2 жыл бұрын

Thank you Glen!

@glennkirilow9015 2 жыл бұрын

@@RobertBolanos You're very welcome!

@SaeidJabbari 5 жыл бұрын

It was as good as ever. Thanks for useful tutorials videos. 🙏🙏🙏

@pentachronic 5 жыл бұрын

Love your explanations. Great educational video. Thanks.

@RobertBolanos 5 жыл бұрын

Thank you Gazza-usa

@vll1976 5 жыл бұрын

Your channel is the best!

@das250250 2 жыл бұрын

Vsat would be i_sat X Zprimary , it can also be measured with a differential probe across primary .

@yaghiyahbrenner8902 3 жыл бұрын

1:28 I would highly stress the point that.. The Rsense resistor used needs to be for best performance a non-inductive type, probably a carbon resistor 3W/5W and maybe a snubber across of 22p or so to tame spikes. That resistor too also acts a magnetic core reset.

@windward2818 Жыл бұрын

The inductance of a transformer primary with an open secondary is just the magnetization current of the transformer primary which is an inductor. So essentially you have a series RL circuit, assuming the MOSFET Rds on can be ignored. Because we have a series RL circuit, the current through the transformer primary and the sense resistor is the same, so we can depict the current in the circuit by looking at the voltage across the sense resistor. What this means is essentially we are looking at the classic LR series circuit current characteristic which should be exponential, and is as shown on the scope. Then as the transformer primary becomes saturated, or, in other words, is unable to store more magnetic flux , the primary reverts to just looking like a resistor as you extend the pulse time. So, after saturation is reached the RL current characteristic becomes linear (a straight line) like in a resistor. Saturation then is determined by looking at the knee (inflexion point) between the exponential and linear current. The inductive kick looks a little large which is due to unclamped inductance, either in the transformer primary leads or the inductive sense resistor or both.

@turkialshehri9762 Жыл бұрын

great video

@flaplaya 4 жыл бұрын

The wire wound resistor is adding a decent amount of inductance. From what I just read that would only be problematic at RF. This is a very interesting lesson that has me kind of puzzled. My thinking would be current falling off with core saturation, not curving up like it does. Great lesson sir.

@RobertBolanos 4 жыл бұрын

fla playa Hi fla, the current goes up because the core is saturated and thus the inductance start to drop exponentially. It some point it stops being an inductor and start to act like a wire. Hope this makes sense.

@flaplaya 4 жыл бұрын

Ah ha I think I just put it all together with your help. Pri current rises as the indunctor of transformer becomes saturated with flux for some reason I was thinking Sec.. I'm going to have to do a lot more research on this. Sec Voltages/currents would be so cool to see as this phenomenon occurs btw. Thank you for the reply Robert, you are highly intelligent.

@flaplaya 4 жыл бұрын

I did just totally get it. Saturate/remove good efficiency of core material the inductance/reluctance fall hence current rise... Love the "Wire" analogy... Greatly appreciated!

@RobertBolanos 4 жыл бұрын

@@flaplaya I am glad my explanation helped.

@Greg_Chase 10 ай бұрын

to really drive this point home - "inductance drops once all the electron spins in the core are aligned (aka once the core is saturated)", have a look at magnetic amplifiers. [NOTE: alignment of electron spins makes the magnetic field strong enough to be detected as a magnetic field around the core; aka "aligned magnetic domains. A saturated core has reached the strongest possible magnetization, ie. all its electron spins are aligned] The magnetic amplifier actually works BECAUSE OF core saturation as follows: 1) normally, an inductor impedes current flow - it takes about five (5) L/R time constants to reach full current flow in an inductor (this is why "current lags voltage" in the inductor). "L" = the inductance value of the inductor. "R" = the resistance. You can look up "L/R time constant" for more info. 2) so you can think of the core as telling the current "look - I'm not just flipping all my electron spins into alignment just because you want to freely flow in the wire - it's gonna take a bit of time to align all my electron spins - and that means I'm impeding your flow through that wire, so hang tight" 3) after all electron spins in the core (the magnetic moment of each electron) are in full alignment, the core can no longer exert a 'damping' effect on the current flow 4) so the "inductance" is just the name for the core material exerting a brief thwarting effect, an interference, over the current freely flowing in the wire A magnetic amplifier works like this: 1) there is a core material 2) a coil is wrapped around it to host AC current flow, just like in a typical inductor or transformer 3) a second wire is also wrapped around or in the vicinity of the core but it hosts DC current 4) the AC is turned on and is THWARTED by the electron spin alignment process described above (thwarted by the inductance) 5) the DC is turned on and PRE-ALIGNS all the electron spins in the core, aka saturates the core 6) that drops the inductance because the core's electron spins are all aligned and can no longer impede current flow 7) suddenly the AC is no longer thwarted by the electron spin alignment process and is AMPLIFIED, increases in magnitude The DC current pre-aligns, aka pre-saturates, the core in order to suddenly remove the thwarting normally seen by the AC Magnetic amplifiers don't amplify a magnetic field, they amplify AC by pre-saturating the core with a DC-powered winding, and thus by removing inductance. But they do that by magnetizing the core to the max (aka saturation) hence the name 'magnetic amplifier' They are also called "Saturable Reactors" .

@ahmedahmed-yg5fl Жыл бұрын

❤❤❤❤ thank you ❤❤❤

@RobertBolanos Жыл бұрын

Thank you Ahmed!

@___Chris___ 3 жыл бұрын

How does voltage fit into this? Is saturation really just the consequence of cumulated current or is it really about the duration of applied _wattage_ ? E.g.: is there a difference how fast the same core saturates whether I have a high voltage and low current on the primary coil versus low voltage with high current (the product being equal)? Second question: what about timing, i.e. what are typical real-life values how fast saturation occurs in gapped vs. non-gapped cores? You mentioned 20µs here, but I don't know what kind of core you're using. For a flyback I guess this would be a gapped core, but how would - at the other end of the spectrum - e.g. non-gapped toroids compare? Are we talking nanoseconds? The reason why I'm asking this is that I wonder whether we can interrupt the circuit shortly before saturation by using a MOSFET that makes use of the voltage across the coil (which should greatly decrease near saturation) as gate voltage. Thanks!

@sam-cj8tf 2 жыл бұрын

Actually love to get this answer answered

@Yorumcu63 2 жыл бұрын

Very important video Thank you.Could you make a video about about "how find SMPS transformer's most effective working frequency "? Actually could you make a video about "What can learn noname a toroide core with scope and function generator? I mean we can learn Al value and how can learn permability and other catalogue specifications? (Maybe you can make quality torode core all specs.know and you could find same specifications ?)

@RobertBolanos 2 жыл бұрын

Great suggestion!

@enochreturn 2 ай бұрын

Hi Robert, Thank you for this video. Question, in the title you mention that this is a transformer and so I am assuming that this is a ferrite material with no air gap. However, in your video you mention that this is an inductor. Is this an inductor with an air gap or a transformer?

@RobertBolanos 2 ай бұрын

Hi Reni, If I recall it had a gap. Adding a gap will make the inductor go into saturation at a higher voltage. If you look at a B vs H curve, the make the slope of the curve less so the saturation happens at a higher H and therefore higher current. I hope that makes sense. Have a good day. RB

@enochreturn 2 ай бұрын

@@RobertBolanos Thank you, Is your Transformer spreadsheet available to dowload?

@RobertBolanos 2 ай бұрын

@@enochreturn I have the flyback spreadsheet that I can sent if you give me your email.

@merden102 5 жыл бұрын

Hi sır. Can you create PFC Circuit video tutorial? Your videos very important for me. Thanks

@RobertBolanos 5 жыл бұрын

Hi Mesut, I intend to do a couple of videos on that subject. Robert

@merden102 5 жыл бұрын

@@RobertBolanos Waiting Impatiently. Thanks sir

@KX36 5 жыл бұрын

When you calculate Isat, you assume no voltage drop across the shunt resistors. I suspect that would be a significant source of error.

@RobertBolanos 5 жыл бұрын

Hi KX36. I did not have a very accurate current sense resistor. I tried to make a current sense using magnet wire but I could not verify such a low ohms with the test equipment I have. So I relied on the Di=(V/L)*Ton to try to calculate the delta current. I have a LCR that is accurate and I rely on the LCR measurement to get accurate enough calculation. I just wanted to be in the ball park; it does not have to be that much accurate. To measure more accurate, use a precision current sense resistor. Thanks for the question! Robert

@KX36 5 жыл бұрын

@@RobertBolanos I don't mean to measure the current accurately directly from the resistor, I mean the burden voltage of the shunt makes up a significant portion of the Vdd you used in the formula since the current is apparently so high. If this is the case, the shunt resistor is acting as a ballast to act against saturation. You can still calculate current with that formula and forego the need for an accurate shunt resistance, but you need to measure the voltage across the inductor only, not just use the supply voltage.

@brokensword5042 5 жыл бұрын

What percentage should the safety gap be between the saturation and operating current? Thanks for video.

@RobertBolanos 5 жыл бұрын

Hi Brokenwords. That is a good question. Isat and Bsat are related. You ussaully use Bsat= (VL*Ton)/(Ae*N). Bsat is given in the core material datasheet. Bsat typically for a ferrite is around 0.3T (teslas). So you can use the same equation to calculate the Nturn and use Boperate = (VL*Ton)/(Ae*N). Per the Abraham Pressmen book, he likes to use 0.16T for Bopeate. That is about 53% of Bsat. You can probably go up to 80% of Bsat. How does that relate to Isat? (Ioperate/Isat)=Boperate/Bmax). This is how they are related. Therefore, Ioperate would be 53% to 80% of Isat. I hope that make sense. Great question and thank you for asking it . Robert Bolanos

@jesselee2529 5 жыл бұрын

@@RobertBolanos I think A. Pressmen used 0.16T for Boperate is because he derated it for 120C operating temperature. To be more precise Bsat = 0.28T for ferrite... that about 57% which seem right... 60%-70% of the room temp capacity seems to be the target number for high temp.

@RobertBolanos 5 жыл бұрын

Jesse Lee thank you for your response. I think Dr. goes as high as 80 % of Bsat. I think that is where I got the 80 percent. Also keep in mind that bsat is also specified at two temperature which one of them is at 100c. So if you go 80 percent at the Bsat specified at 100c you should be Ok. The only time you would go 80 percent is if you are trying to fit many turns into a core. If that is the case, might as well use a bigger core. Again thank you for your inputs. Robert

@zenerassaf2490 3 жыл бұрын

👍 analyze

@coucouj2781 Жыл бұрын

Sir what is “E” in your equation?

@RobertBolanos Жыл бұрын

E is the voltage. Sorry for the confusion.

@hadighaemipoor6354 5 жыл бұрын

Only good

@ahmetaltan3203 3 жыл бұрын

Please add schematic

@coucouj2781 10 күн бұрын

Would that be Bmax (or Bsat)?

@RobertBolanos 10 күн бұрын

Bsat

@coucouj2781 10 күн бұрын

Would you be able to make a video on how to find bsat of an unknown ferrite core?

@coucouj2781 10 күн бұрын

I meant Bmax

@RobertBolanos 10 күн бұрын

@@coucouj2781 You can use the same procedure I used here and calculate it

@coucouj2781 9 күн бұрын

Thank you for the precision, but now I'm a bit confused between Bsat and Bmax. Aren't they the same, where it represent the maximum saturation level that core can handle?