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transformer phase shift - how to measure with oscilloscope
3

transformer phase shift - how to measure with oscilloscope

transformer phase shift - how to measure with oscilloscope

(OP)
I know this might seem like a schoolboy level question, but I'm afraid I'm stuck.

If I have an unknown transformer and what to determine if there is a phase shift, how can I do it with my two channel scope, considering both channels use the common ground, and so by connecting two channels I am really creating a direct physical connection between the two otherwise isolated primary and secondary coils.

Thanks

I think I am going to be embarassed by the simple answer.

RE: transformer phase shift - how to measure with oscilloscope

Are you trying to prove relative phase, i.e. 0° or 180° phase primary to secondary, or actual phase shift due to the transformer? The former is fairly straightforward, the latter is more demanding on your instruments and the answer, when/if you get one, isn't a constant.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
It is just the former thanks.

RE: transformer phase shift - how to measure with oscilloscope

Connect one end of the primary winding to one end of the secondary winding.
Energize one winding, either one. The voltage may be equal to or less than rated voltage.
Measure the voltage across the primary.
Compare that to the voltage across the free ends of both windings.
If the voltage across the free ends is more than the voltage across the primary the windings are 180 degrees out of phase relative to the common connection.
If the voltage across the free ends is less than the voltage across the primary the windings are in phase relative to the common connection.
You can use the scope to measure the voltages, but I would use a voltmeter.
Or you can use the two channels to compare the waveforms.

Quote (OP)

so by connecting two channels I am really creating a direct physical connection between the two otherwise isolated primary and secondary coils.
Create the physical connection before you connect the scope.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

Beat me to it Bill. Thanks. smile

RE: transformer phase shift - how to measure with oscilloscope

(OP)
That's great. Thanks X 2

RE: transformer phase shift - how to measure with oscilloscope

(OP)
So, just to follow up on this subject.

I have two further questions.

I have got hold of a toroid from my supply of scrap.

It has 14 turns on the primary, and 14 turns on the secondary.

They are wound, one LH and the other RH, so the input and output are in phase.

1. So my first question is, what is this arrangement called?

Is it simply an isolation transformer, or does it do some filtering also, or a bit of both?



2. After doing some unwinding / rewinding / phase measurements with this toroid, my second question is this.

If I have transformer in which I wound one winding in reverse by mistake, is it simply a case of swapping the terminals on the output or input stage, to get the thing back into the correct phase? This is only hypothetical, and I realise some tappings which are not true centre tappings would get all messed up by simply swapping terminals. But in an example such as this toroid detailed above, can I simply swap the output terminals, as opposed to unwinding / rewinding it in reverse? Is there something I am unaware of that means I can't simply swap the terminals?

Thanks

RE: transformer phase shift - how to measure with oscilloscope

1) If the windings are not touching each other electrically then it's an isolation transformer.

2) Yes, you can just reverse the connections. You should note that many transformers and transformer symbols sport dots.


The dots are the wires that will have the same phase polarity. Rising waveform on primary dot results in the same rising waveform on the secondary.



The dots denote the phasing between the windings. About half the time you could care less as it just doesn't matter but other times it's critical and a complete disaster will befall the transformer, the circuit, the function, safety, and sometimes the people standing nearby.

I was told about a very large PG&E transmission transformer in a substation by a guy present when the new transformer was energized for the first time. It was explained to me that the 100+MVA transformer was energized, made a horrible groaning sound that sent everyone fleeing and promptly blew up, he actually said, "lifted inches off the pad". He said it turned out to be a manufacturing defect that had the DOT on the wrong terminal. I believe now days they actually don't trust this and test the transformers before closing switches.

Keith Cress
kcress - http://www.flaminsystems.com

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Thanks for that. I am planning on making a DC DC converter, so I know it is critical in this case to get the dots right. I'm just playing with some scrap at the minute to understand it better. I'm only working with 12V and a few milliamps on the primary, so I don't think I'll blow myself up smile not yet anyway. Thanks

RE: transformer phase shift - how to measure with oscilloscope

Quote (OP)

...with my two channel scope, considering both channels use the common ground, and so by connecting two channels I am really creating a direct physical connection between the two otherwise isolated primary and secondary coils.

Assuming that the transformer is essentially sitting on a bench (otherwise isolated from any grounding), then there's no issue with applying a common ground (i.e. your grounded input signal source and your grounded 2-channel scope) to simply and directly compare the phasing. Your 2-channel scope would show the two waveforms, either in-phase or out-of-phase. If out-of-phase, then swap the secondary leads (and then recheck if you wish). Perfectly straightforward.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Thanks. I did a few tests and it all makes sense now.

RE: transformer phase shift - how to measure with oscilloscope

Dear OP, I have been wondering about this thread. It started innocently and, for a mechanical engineer, not so bad. I would probably ask something similar if I was to find out if a transmission reverses rotation or not.

But now, I understand that you are going to make yourself a DC-DC converter with that transformer. And that is a quantum jump. Or a triple quantum jump. With peak. Be prepared to ask many more questions. One that I need to ask is if the core material at all is suited for that? Sounds like ordinary transformer plate to me. Another one is if losses and regulation is important or not? And still one is what frequency do you plan to run it at? There could be more questions asked - like that of leakage inductance, ringing, core saturation, flux symmetry. And still some.

You may find that your first question was the easiest to answer. So, you will learn a lot by doing. But it will take time. Some say learn by burning. And that is not at all unusual. Not even at 12 V.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

Reversing polarities of a winding:
Some power transformers at higher capacities and voltages may have graduated insulation.
Reversing connections may result in a higher voltage to ground than a part of the winding is insulated for.
If the winding is uniformly insulated there is no issue reversing the connections.
Be aware that the construction of some large, high voltage transformers may be a bad idea.
Also in large transformers there may be issues with the length of leads between the winding ends and the appropriate bushings if the connections are reversed. Longer leads may not have the strength required to withstand the forces of fault currents.
This won't apply to you MRSSPOCK, but others are following this thread also.
What is acceptable for small transformers may not scale up to all very large transformers.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Well, for anyone curious to know what I'm up to, I would like to learn more about transformer design. Even the basics. It seems like a nightmare no matter where I look to learn the theory. I was rummaging through my scrap to see if there was anything I could learn from, as I do actually find that I learn better from burning smile So, I found in my scrap an old strobe light, or timing light, for setting car ignition timing in the olden days. I am planning to reverse engineer it to see what is going on, then try to get my head around the DC to DC conversion part of it, by first learning the basics of how a toroid behaves when I do certain things to it, then do some testing of the existing transformer in the timing light at its operating frequency, (and some other frequencies, etc), then after all that, see if I have learned enough to design something of my own, without simply doing a copy of what I have. It is all academic. I tried for quite a while to understand the theory, but I just always seem to be missing some variables in understanding it all. It seems that fuzzy area is probably the reason why there is simply no on line design program that lets you feed in the variables, then get a design spat out. I wouldn't really want that anyway, since with the possibility of actually burning my house down with a bad transformer design, I think I would like a little bit more confidence in what I'm doing! I know I have a LOT to learn but I have to start somewhere. I have downloaded the TDK EPCOS pdf with about 625 pages, so that should hopefully keep me scratching my head for a few years (or decades more like it). Watch this space, but don't be expecting any major events in the near future other than my house burning down maybe smile

And for anyone wondering what my incompetence level is, here is my first learning experiment smile



I will never forget this now after doing it in person. All those left and right hand rules were doing my head in. I now know if I wind a wire onto a common right hand threaded screw, and I treat the screw head as the ground, the end of the screw creates a South pole.

RE: transformer phase shift - how to measure with oscilloscope

If you're wanting to learn about HF transformer design then the old Philips (Ferroxcube) MA01 databook isn't a bad starting point. They turn up from time to time because no one wants paper books anymore.

The text 'Soft Ferrites' by Edgar Snelling is a little dated in terms of materials but is a superb reference on ferrite transformer and inductor design. The newer power ferrites such as 3C90 and 3C95 aren't listed but the principles all still apply. It's long out of print and used copies command a fair premium which is testament to its quality.

Ferroxcube's own website looks worth a browse - I haven't been in the power electronics game for a good few years but from a quick look on their website they have some reference material and some sort of design tool / design aid which you can download.

RE: transformer phase shift - how to measure with oscilloscope

A very commendable approach!

If you find the TDK/EPCOS 600+ pages hard to digest in one or two bites, I recommend Jim Williams' (LT staff scientist who sadly passed away when wrestling with a Fluke scope's SW problems, my guess) paper on switchers. I will look for it. A quote: "If the core feels right, has a nice weight and the Windings seem to be able to carry the current needed, then look no further. Just try it!"

I will look for that paper (a few pages) for you.

Good luck. And remember that the North Pole actually is a South Pole. By definition.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

I'm not sure there's much DC-DC going on, inside a strobe light. As seen in http://www.circuitdiagramworld.com/led_circuit_dia... or http://www.circuitdiagramworld.com/monitor_circuit... the objective is to get the electrical pulse to stretch out, but still be a pulse that's long enough for the light to register with your eyes.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Thank you for your encouragement.

@IRstuff, my timing light is powered from the car battery, and steps the voltage up to about 350V, (via the DC-Dc converter) and stores it in a 2.2µF cap (450V), until it gets triggered by the inductive pickup (attached to the HT lead), by means of a SCR, which dumps the charge through another device (I'm guessing another transformer), and subsequently to the "bulb" for want of a better word.

RE: transformer phase shift - how to measure with oscilloscope

2
I Think that this is the one I was referring to:

http://www.analog.com/media/en/technical-documenta...

It has been augmented somewhat. The title "Switching Regulators for Poets" is typical for Jim. I miss him a lot. And Bob Pease, who died when returning home from Jim's funeral ceremony.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

Quote (GE)

And Bob Pease, who died when returning home from Jim's funeral ceremony.

That was a very sad week. Several of us in my office were in mourning, those that knew of them.

Somewhere I have a letter from Bob Pease.

RE: transformer phase shift - how to measure with oscilloscope

Yes, I knew them both. I corresponded with Bob and appeared in a few of his "What's this xxx stuff, anyhow". He even sent me a card when I was at hospital for a by-pass surgery. He had so much time for everyone.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

Many DC-DC converters are not isolating and use only an inductor (single winding), not a transformer. Design still involves dealing with the magnetic properties of the core and coil.

A really nifty control IC is the LTC3780. YouTube has some great explanations of how it can smoothly transition between buck and boost. It's certainly interesting. eBay sellers offer preassembled modules for ~US$10+ price class.

RE: transformer phase shift - how to measure with oscilloscope

Quote (https://en.wikipedia.org/wiki/Jim_Williams_(analog...))

Jim Williams (analog designer)
From Wikipedia, the free encyclopedia

Jim Williams
Born April 14, 1948
Died June 12, 2011 (aged 63)
California
Nationality American
Occupation Electronics engineer

James M. Williams (April 14, 1948 – June 12, 2011) was an analog circuit designer and technical author who worked for the Massachusetts Institute of Technology (1968–1979), Philbrick, National Semiconductor (1979–1982) and Linear Technology Corporation (LTC) (1982–2011).[1] He wrote over 350 publications[2] relating to analog circuit design, including 5 books, 21 application notes for National Semiconductor, 62 application notes for Linear Technology, and over 125 articles for EDN Magazine.

Williams suffered a stroke on June 10 and died on June 12, 2011.

Quote (https://en.wikipedia.org/wiki/Bob_Pease)

Bob Pease
From Wikipedia, the free encyclopedia
Jump to navigation
Jump to search
Robert A. Pease
Full face portrait, showing mature glasses-wearing adult male with white hair and a full white mustache and long beard
Born August 22, 1940
Rockville, Connecticut
Died June 18, 2011 (aged 70)
Saratoga, California
Nationality American
Other names Bob Pease
Alma mater Massachusetts Institute of Technology
Occupation Electronics engineer
Known for Analog integrated circuit design, technical author

Robert Allen Pease (August 22, 1940 – June 18, 2011) was an analog integrated circuit design expert and technical author.[1][2] He designed several very successful "best-seller" integrated circuits, many of them in continuous production for multiple decades. These include the LM331 voltage-to-frequency converter,[3] and the LM337 adjustable negative voltage regulator (complement to the LM317).
Contents

1 Life and career
2 Death
3 Publications (partial)
4 See also
5 References
6 External links

Life and career
Pease was born on August 22, 1940 in Rockville, Connecticut.[4][5] He attended Northfield Mount Hermon School in Massachusetts, and subsequently obtained a Bachelor of Science in Electrical Engineering (BSEE) degree from Massachusetts Institute of Technology in 1961.
...............
My favorite programming language is ... solder
...............
Death
Flag at half-staff at National Semiconductor on June 21, 2011

Pease was killed in the crash of his 1969 Volkswagen Beetle, on June 18, 2011.[25][26][27] He was leaving a gathering in memory of Jim Williams, who was another well-known analog circuit designer, a technical author, and a renowned staff engineer working at Linear Technology. Pease was 70 years old, and was survived by his wife, two sons, and three grandchildren.[27] The sudden death of Pease triggered a small flood of remembrances and tributes from fellow technical writers, practicing engineers, and electronics hardware hacking enthusiasts

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

"Good luck. And remember that the North Pole actually is a South Pole. By definition. "Sometimes called the "North seaking pole."
Brings back memories of the years when we were taught to use our left hands for the right-hand-rule. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

(OP)
I think a miracle might be in order, never mind "good luck" !

What surprises me is that with transformers so widespread, (there are probably 50 in the room I'm now sitting in, within various appliances), that the design of such seems to have even many professionals view the transformer design with "Trepidation". Surely the world must be full of transformer designers who know precisely what they are doing, and the mystery is, how has this knowledge not now become common and widespread? Is it because it really is complicated, or they like to keep it a secret smile

RE: transformer phase shift - how to measure with oscilloscope

"Surely the world must be full of transformer designers"

Why do you think that? Few consumer systems that require transformers are seriously constrained by size, weight, and power. And why would a walwart designer design their own transformer when they can order one that close to their needs, off-the-shelf? No designer in their right mind would contemplate designing and manufacturing their own transformers, for the same reasons they wouldn't contemplate designing and manufacturing their own capacitors, resistors, inductors, or transistors.

And, for the most part, transformers are not an avenue for new design explorations, just like no one contemplates designing new resistors or capacitors. We've been using the mostly same dielectrics for probably 40 years. Supercaps are probably the biggest deviation from that, and they're a pretty niche product.

In a similar vein, could you, would you, design and fabricate the 1/4-20 screw in your picture from scratch for your next project?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: transformer phase shift - how to measure with oscilloscope

Wow, 7 years already since we lost those two. Seems like yesterday...

Z

RE: transformer phase shift - how to measure with oscilloscope

(OP)
@IRstuff

I just assumed that transformers had to be tailored more precisely to certain applications, but from what you state, they are generally chosen as the best available for the purpose required. Having said that, Farnell. RS etc, do sell hundreds of options of coil formers. ferrites etc, in quantities less than 10. I wonder who their target market is.

As regards threads, I regularly need to cut some bastard thread to match up with some already existing component, generally someone has cut a metric thread onto some vintage machine component. 1.75" x 1.5mm pitch, just last week for example.

RE: transformer phase shift - how to measure with oscilloscope

I have cut a few threads. I use off the shelf dies and taps.
I had one application where a machine shop made an adapter to fit a replacement part with a right hand thread onto a part with a left hand thread.
Never any design involved, just followed existing practice.
Back to transformers.
Some basics:
Core permeability flux density and saturation.
Amp turns.
Taken together, more Amp turns means higher flux density until the limit is reached at saturation.
Use this information to calculate the inductive reactance of the transformer, viewed as an inductor at a specific frequency.
Now use this to calculate the voltage required to push the core to saturation.
With voltage and frequency, calculate the Volts per Hertz ratio.
The Volts per Hertz ratio will tell you the safe operating voltage over the linear range of the core.
There is more but that will give you a start.


Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Thanks for all your advice, comments, links, pdf's etc. All good stuff. Time to get my head down now and generate some smoke!!!

RE: transformer phase shift - how to measure with oscilloscope

It's not uncommon to wind one's own custom transformers for RF projects. These days they'd typically be of the toroid ferrite-core variety, or in previous generations (e.g. 1950s) they might have been air core. Commercial products (radios) would more-typically use Off-The-Shelf transformer 'cans'. For an existing design, just follow the build instructions to wind the coils. For something of your own design, the core company (e.g. Amidon Associates) provides data sheets and plenty of 'White Paper' guidance.

Modern DC-DC converters are somewhat similar. If you're building a one-off example, then you might choose to find a suitable core and wind your own coil. Or just purchase a pre-wound inductor (or extract one from a junked PC power supply). As mentioned already, many DC-DC converters are non-isolating and use only a (single winding) inductor (not a transformer).

RE: transformer phase shift - how to measure with oscilloscope

I'll second the plug for Amidon. Their Tech Data Flyer is still useful after 17+ years!

Z

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Sorry for asking this question here, but I can't find any forum administration type contact, so my question is, is there a means to send a Private Message on this forum? I can't find any way to do it. Thanks

RE: transformer phase shift - how to measure with oscilloscope

Mrsspock:
Are you concerned with a 50/60 Hz transformer or an RF transformer?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

(OP)
No, I simply wanted to run something past an individual. Not for technical advice, more for administrative forum advice. Not to worry.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
So, I've had a slight change of direction on this matter. Instead of using my old strobe light, I bought one of these from ebay. (I presumed the output would be AC but it isn't).



I have an idea, which might help anyone else who would like to learn more about this subject.

I have already pulled this device apart and taken a photograph of both sides.

I inverted the reverse side so as to give me a view as if I am looking straight through the board.

I then placed both images beside one another, so as to provide a TOP view and BOTTOM view, to make reverse engineering it a bit easier.

Using DIPTRACE I then superimposed the relevant components roughly in their locations, then wired it all up.







(Maybe this is a clearer image for the components names - I can't seem to make it use up the page width)




So, suppose some one of you who has a reasonable understanding of this circuit, is willing to help me along as I recreate this circuit on a breadboard, and provide a means whereby I can tweak certain components / parameters, and observe the output.

It might serve as a good reference for someone else likely to make all the cock ups I am about to make.

I purposely said that if some ONE of you, because quite honestly, I think the whole exercise would just turn into mayhem, if I was getting advice from 10 different inputs, possibly many pointing me in many different directions.

(Is it maybe even better that this would be done off line, then the final result uploaded at the end?)

The device is on ebay is only £4 so it is dead easy for someone else to easily join in and hack up one for themself, if they too are keen to use the "learn by burn" process.

The first thing I want to do, is to ditch all the parts that relate to the USB output, but to be honest, my first hurdle is understanding how this circuit works. I can understand a basic oscillator but how this Zener is positioned is confusing me. I'm pretty confident that all my components on my schematic are listed correctly, except for two items.

1. I am presuming that is a 7.5 Zener diode.

2. The transformer dots are just as was the default from the component library in Diptrace.

If anyone can spot any immediate cock ups in how I have captured the schematic can you please point it out. (Thanks).

So if anyone has any comments, and anyone feels like volunteering to be my mentor, please feel free to take the plunge!

It might all turn into a big mess pretty quickly, but I'm ready to do the donkey work, if it seems a useful exercise to any of you.

RE: transformer phase shift - how to measure with oscilloscope

Better than a cross-Word puzzle! This drawing may be easier on the Eyes:


I would run that on LT Spice if I had the time to do it. Anyone?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
@ IRStuff

Yes thanks, you are correct.

The USB shield and USB ground are tied to that node.

I did a test, and with no load on the USB port, the output voltage is 6.5V, whether connected to the USB ground or the boards groundplane.

I then put my probes between USB ground and the board grounplane and read 0.0V

I will try to create a better image. That is hard to read.

Thanks

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Hopefully this is clearer.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
@ skogsgurra

Diptrace has some export options.

Do any of these provide a means to create a file to run LTSPICE ?

I heard of LTSPICE but never used it or seen it used.



RE: transformer phase shift - how to measure with oscilloscope

Spice Netlist should work. LT Spice is a "Clean" Spice with a huge library of (mostly) Linear's Components. But also quite a few "generic" components. Give it at try. You can't lose - if your time isn't extremely valuable...

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
So, I had a go with LT Spice, but can't seem to get the transformer to output anything.
To be honest, Im not so sure I've set it up correctly.
Would anyone care to try running this please.
There are 4 components I haven't selected exactly properly as I couldn't find the specific components, but am confident the others are ok.

C1
C2
D4
Q1

Then I'm not sure if I have configured T1 correctly.

The first portion of code below is the code generated and stored in the *.net file.
I see it lists .model NPN, then PNP. I don't know why that is.



* \\PC1\Users\mrsspock\My Documents\LTspiceXVII\Draft1.asc
R1 N002 N003 27k
R2 N010 N006 220
R3 N001 N009 100k
C1 N003 N006 0.0047µ V=200 Irms=247m Rser=0.679706 Lser=0 mfg="KEMET" pn="C1210C472K2RAC" type="X7R"
C2 N002 N005 0.0047µ V=200 Irms=134m Rser=1.30834 Lser=0 mfg="KEMET" pn="C0603C472K2RAC" type="X7R"
C3 N008 N007 10µ V=25 Irms=39m Rser=2.8 Lser=0 mfg="Nichicon" pn="UPR1E100MAH" type="Al electrolytic"
C4 N011 N006 47µ V=35 Irms=115m Rser=1 Lser=0 mfg="Nichicon" pn="UPR1V470MPH" type="Al electrolytic"
C5 N001 0 2.2µ V=100 Irms=22m Rser=9.8 Lser=0 mfg="Nichicon" pn="UPR2A2R2MAH" type="Al electrolytic"
Q1 N005 N003 0 0 2N2222
D1 0 N011 1N5819
D2 N010 N003 1N4148
D3 N007 N006 1N4148
D4 N004 N001 RF01VM2S
D5 N009 0 QTLP690C
D6 N007 N003 BZX84B7V5L
L1 N005 N002 100µ
L2 N006 N008 400µ
L3 0 N004 40000µ
V1 N002 0 12
.model D D
.lib \\PC1\Users\mrsspock\My Documents\LTspiceXVII\lib\cmp\standard.dio
.model NPN NPN
.model PNP PNP
.lib \\PC1\Users\mrsspock\My Documents\LTspiceXVII\lib\cmp\standard.bjt
* 300V DC out
* USB Gnd
* USB out
* Gnd
* 12V DC in
;op
K1 L1 L2 L3 1
.op
.backanno
.end



**********************
and below here is the data from the asc file - the circles are only there to remind me that those features need revisited / corrected
**********************

Version 4
SHEET 1 1920 824
WIRE -32 -640 -144 -640
WIRE 1312 -640 -32 -640
WIRE 1616 -640 1312 -640
WIRE 96 -512 -640 -512
WIRE 192 -512 96 -512
WIRE 96 -432 96 -512
WIRE 1312 -400 1312 -640
WIRE -144 -352 -144 -640
WIRE 96 -224 96 -352
WIRE 1024 -224 96 -224
WIRE 96 -192 96 -224
WIRE 192 -176 192 -512
WIRE 480 -176 192 -176
WIRE 1312 -128 1312 -336
WIRE 1312 -128 640 -128
WIRE 192 -96 192 -112
WIRE 480 -96 192 -96
WIRE 480 -64 272 -64
WIRE 1312 -48 640 -48
WIRE 96 16 96 -128
WIRE 288 16 96 16
WIRE 480 16 352 16
WIRE -640 32 -640 -512
WIRE -32 48 -32 -640
WIRE 192 96 192 -96
WIRE 1168 96 192 96
WIRE -144 192 -144 -272
WIRE 752 256 416 256
WIRE 1024 256 1024 -224
WIRE 1024 256 816 256
WIRE 96 288 96 16
WIRE 1168 336 1168 96
WIRE 96 384 96 352
WIRE 272 384 272 -64
WIRE 272 384 96 384
WIRE 416 384 416 256
WIRE 416 384 272 384
WIRE 640 384 416 384
WIRE 880 384 720 384
WIRE 1024 384 1024 256
WIRE 1024 384 944 384
WIRE 1104 384 1024 384
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SYMBOL polcap 352 0 R90
WINDOW 0 0 32 VBottom 2
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SYMATTR Description Capacitor
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SYMBOL polcap 432 496 R180
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SYMATTR Value 47µ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=35 Irms=115m Rser=1 Lser=0 mfg="Nichicon" pn="UPR1V470MPH" type="Al electrolytic"
SYMBOL polcap -48 48 R0
WINDOW 3 24 56 Left 2
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SYMATTR Value 2.2µ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=100 Irms=22m Rser=9.8 Lser=0 mfg="Nichicon" pn="UPR2A2R2MAH" type="Al electrolytic"
SYMBOL npn 1104 336 R0
SYMATTR InstName Q1
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SYMBOL diode 880 400 R270
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SYMBOL diode 1328 -336 R180
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TEXT 1640 -640 Left 2 ;300V DC out
TEXT 1536 784 Left 2 ;USB Gnd
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TEXT 1520 704 Left 2 ;Gnd
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TEXT 488 -248 Left 2 !K1 L1 L2 L3 1
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CIRCLE Normal 864 336 704 208 2
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RE: transformer phase shift - how to measure with oscilloscope

That's true. There is no thermal noise in LT Spice. Try adding some low-level noise (which I havent been able to find in the component library) or a small pulse a few milliseconds ino the simulation run.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Is this not a basic oscillator which seems to run ok?

Version 4
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WIRE 240 64 240 16
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WIRE 240 160 240 144
WIRE 384 160 240 160
WIRE 432 160 384 160
WIRE 240 192 240 160
WIRE 384 224 384 160
WIRE 128 240 64 240
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WIRE -16 320 -16 144
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WIRE 240 320 -16 320
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WIRE 384 320 240 320
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FLAG 240 352 0
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SYMBOL ind2 112 48 R0
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SYMATTR SpiceLine Rser=0.001 Rpar=0 Cpar=0
SYMBOL ind2 256 160 R180
WINDOW 0 -29 54 Left 0
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SYMATTR SpiceLine Rser=0.001 Rpar=0 Cpar=0
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SYMATTR InstName Q1
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SYMATTR InstName R1
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SYMBOL LED 368 224 R0
WINDOW 0 -54 -412 Left 0
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SYMATTR Value NSPW500BS
TEXT 72 -136 Left 0 !K L1 L2 0.999999999999999999999
TEXT 48 -104 Left 0 !.tran 0 0.00003 0 startup
TEXT 128 256 Left 0 ;Base
TEXT 240 200 Left 0 ;Collector
TEXT 248 288 Left 0 ;Emitter

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Well, I have done some editing to the LTSPICE file, and have whittled it away bit by bit, until I am left with nothing but a single inducter and a 12V DC supply.
But strangley, even then, when I run the simulation, it saturates instantly.
Obviously that isn't possible in reality.
I tried huge Henry values and it is exactly the same as with minute values.
Can someone please suggest what I might be doing wrong?

I have in my hand an actual inductor which is 16mH. When I connect this to a 12V battery it saturates in 10ms at about 1.9A
Surely something as simple as this should be easy to simulate, but even then when I model it, it also saturates instantly, so I am obviously not using LTSPICE properly.

Any suggestions?
Can anyone model that please, since it is only two components and takes ten seconds.
Thanks

RE: transformer phase shift - how to measure with oscilloscope

(OP)
I got it sorted.
The initial voltage needs to be set at 0V for the start of the simulation run.
The simulation does match reality pretty well now.

RE: transformer phase shift - how to measure with oscilloscope

Steady state is not the same as saturation.
Your numbers are not working for me.
I calculate that it will take about 0.5 seconds to reach steady state.
Where did I go wrong?
12 Volts / 1.9 Amps = 6.32 Ohms.
6.32 Ohms x .016 Henrys = 0.1 = 1 Time constant
0.1 seconds x 5 = 0.5 seconds = 5 time constants to reach steady state.
When the magnetic core saturates, the inductor behaves as an air core inductor for further increases in voltage and the induction may drop be as much as 4 orders of magnitude for further increases in voltage.
Your trace is not showing saturation.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

(OP)
Thanks.
Sorry, I thought they were the same.
So, I will rephrase it to say, my 16mH (motorcycle ignition) coil provides a steady state oscilloscope trace, (monitoring current with an amp probe), of around 1.9A after 10ms, when connected to a 12V 7Ah battery (which is registering about 11.5V - it needs a charge).
I measure the coil with an LCR meter, which gives me a series resistance value also of 5.03 ohms, and a capacitance of 15uF.
To be honest, I only just bought this LCR meter so I am still trying to make sure I am using it correctly, but that's the numbers it gives me at the minute. Those are the values I put into LTSPICE to get the trace shown in my last post.

RE: transformer phase shift - how to measure with oscilloscope

A capacitance of 15 uF? Not possible. Interwinding capacitance is in the pF (millionth of a uF) order and total capacitance ocross all windings is even less. Did you use that capacitance in the Spice model? BTW, 11.5 V from a 2 A loaded 7 Ah ackumulator isn't bad at all.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
oops... I was using the LCR meter incorrectly, so I have simply removed the parallel capacitance value.
The 4.9 ohms resistance was measured using a Fluke multimeter, and the 16.624mH using DER EE LCR meter.
When I plug these values into LTSPICE, the results are pretty close to the trace as recorded in the real world on the scope.
I thought that was good, but I don't undestand the different equations shown above.
@IRstuff What should be 2.5ms ? Do you refer to the same quantity that waross says should be 500ms ?
Below is shown the values defining the inductor and the resulting trace.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
@IRstuff
Thanks. It makes a bit more sense now, and I now realise my confusing steady state with saturation. So then, 5 time constants of 2.5ms = 12.5ms which does agree with the simulation, and with the actual coil test. I didn't take any screen grabs of the actual coil test so I will set it up again soon to do that. Thanks everyone for bearing with me. I did state at the outset, that I do really possess quite a high level of incompetence smile

RE: transformer phase shift - how to measure with oscilloscope

Quote (Waross)

Where did I go wrong?
Thanks for setting me straight IRstuff.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: transformer phase shift - how to measure with oscilloscope

"I didn't take any screen grabs of the actual coil test so I will set it up again soon to do that"

Sorry to have done that already. This shows the same inductor in two different time scales (5 and 20 ms/div):



Tha data are 10 ohms, 11.5 V and 19 mH. The effect of high initial permeability can be seen in the 5 ms/d curve where di/dt is low during the first few milliseconds and then goes into a more constant L region.
No saturation in this run, that would have shown as an increased di/dt near end of curve.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

Hmm… Have to check the numbers. I measured inductivity with 50 Hz AC. Doesn't seem right.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
@skogsgurra When I did the coil test, I was simply switching the coil on and off with an IGBT, so I guess my scope trace will be different to that if I had been feeding the coil a sine wave voltage like your one with the AC supply. I still haven't got a chance yet to repeat that test.

RE: transformer phase shift - how to measure with oscilloscope

(OP)
So here is the screengrab from the actual coil test. The horizontal markers on the oscilloscope screengrab are set at 10ms apart, then aligned with the LTSPICE 10ms markers. I did stretch the image in the vertical direction, as the actual recorded current was only 1.8A

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