I think I understand- you are measuring the induced voltage in the chassis from the transformer. Its sort of a proxy for radiated flux. None of the transformers you measured have measures for reducing external fields, although those do have mixed results.
The flat pack will have the highest radiated fields since it has a less efficient magnetic circuit. However it may have higher isolation between input and output electrically. The toroids tend to have the highest coupling between input and output.
The flat pack will have the highest radiated fields since it has a less efficient magnetic circuit. However it may have higher isolation between input and output electrically. The toroids tend to have the highest coupling between input and output.
Richard, surely you exaggerate. I sell audio products all over the world and they are not listed by UL. It would be impossibly expensive to do so. However, it could well be that somebody, somewhere, will INSIST on a UL listing of the CTC Blowtorch, but I just won't sell them one, in that case.
Dick, there is a trace in all the plots with the transformers without power. This gives a good idea as to the baseline for measurement artifacts.
A question I have for Ed, thanks by the way for doing this interesting work, is the following. It appears that transformers that are closest to the torroid topology perform best on this test, which makes sense if you think about the orientation in which the magnetic field is contained. However, the results may be very different on different axis. You know what rotating a transformer may do to reduce hum in an actual enclosure.
A question I have for Ed, thanks by the way for doing this interesting work, is the following. It appears that transformers that are closest to the torroid topology perform best on this test, which makes sense if you think about the orientation in which the magnetic field is contained. However, the results may be very different on different axis. You know what rotating a transformer may do to reduce hum in an actual enclosure.
I can see that.
Next would be what to do to minimise the new unwanted induced freqs that are shown... . Starting by using the best xfmr with minimum radiated field. Various forms of shielding methods have worked well.
Thx-RNMarsh
Last edited:
Nope... from experience. You take your chances.
For DIY who dont actually know how to make a safe built product should be careful and use UL parts on ac line voltage parts.
Thx-RNMarsh
Richard, you are most probably right about the UL listing. I did have one close call, where a distributor, after ordering perhaps 10 Blowtorches tried to get one at deep discount, in lieu of me getting a UL listing. Kind of like blackmail.
However, it is almost impossible to afford the listing of a custom design, and it is kind of useless, IF you know what you are doing. However, I would get the appropriate UL standard and make sure that I met their requirements. That is all they are going to do, anyway, but unfortunately, they have to make a living and things get drawn out. Trust me, I have seen it happen, and I have heard some horror stories about Dyna trying to get listed.
However, it is almost impossible to afford the listing of a custom design, and it is kind of useless, IF you know what you are doing. However, I would get the appropriate UL standard and make sure that I met their requirements. That is all they are going to do, anyway, but unfortunately, they have to make a living and things get drawn out. Trust me, I have seen it happen, and I have heard some horror stories about Dyna trying to get listed.
See wikipedia ---> China_Compulsery_Certification. Been in effect since 2003. Ditto EU. If you import a low enough volume you could apply for an exemption.
That has nothing to do with DIY building though. Be safe and use qualified parts for the high voltages parts of the build.... from the plug and cord thru to the transformer and any filters, fuses, switches, wire used in between.
-RNM
Last edited:
Richard,
I am sure you are correct about getting a product certified if you want to sell into the international market and I could imagine the lawsuits here in the USA if someone got hurt or there was a fire due to a product not meeting UL requirements. I might not be a circuit designer but I do have a good idea what not to do when testing live equipment. I used to have to trouble shot some of my own equipment which were mostly 480V three phase and one machine was rated 480v, three phase, 85kw draw by itself. Don't make a mistake while working on something like that, you only get one mistake and then you don't have to worry about that ever again!
I am sure you are correct about getting a product certified if you want to sell into the international market and I could imagine the lawsuits here in the USA if someone got hurt or there was a fire due to a product not meeting UL requirements. I might not be a circuit designer but I do have a good idea what not to do when testing live equipment. I used to have to trouble shot some of my own equipment which were mostly 480V three phase and one machine was rated 480v, three phase, 85kw draw by itself. Don't make a mistake while working on something like that, you only get one mistake and then you don't have to worry about that ever again!
Or a sheep.I guess I would come back as a cow then....
An electric sheep !
Its a headsup for everyone... your working on power transformers will eventaually lead to other areas for solutions which can be followed by readers of the forum. So for them it was meant. And, for all the other projects they build. -RNM
Well, I don´t argue with this as a design decision, but the test case was completely unrealistic.
BTW which levels of distortion would a non feedback MC stage (like in the Vendetta) produce
under the _very same_ test conditions (200 mV(!) in at 10Hz I believe it was) ?
I am a transmutated creature, charged for ever,after surviving an 145kV capacitance one side discharge blow.
Correct.
But whether UL rated or not, with time and use, HV circuitry and heat generating areas will suffer from dust attraction. My experience with dissecting damaged equipment, tells me that regular cleaning these areas would have prevented catastrophic and dangerous failures.
Ed thanks for sharing.
Wide spreading of freq. peaks suggests edges on the waveform.
Studying the shape and location of distortion in the waveform may tell a lot.
The spectrum of the unloaded case indicated the magnetic core is saturated by the magnetizing (idle) current. Check the waveform for flat top and bottom peaks. Increasing ~10% the primary turns usually cures it.
3rd, 5th and 6th attached FFTs show quite a difference in loaded condition rel unloaded. I am not sure on this but I suspect close primary/secondary winding coupling and/or load is high for the trafo.
George
PS Test lead shown here
form a large loop. This way your set-up is sensitive to other magnetic pick-ups in addition to the intended one (voltage across the chassis). Shielded separate leads may be better for the purpose.
Last edited:
John, thanks for the explanation that I can understand your steps in the way of designung.
It's normal that most designer "idealize" their practice how it has to be done. Anyway what meaures very good must not sound good - sometimes there is a difference.
However,sometimes I like to get some statements during the prototype phase as well and it could be helpful.
- Status
- Not open for further replies.