nelson-
ok i'm not to bright am i? i was reading your post again and thought you might be meaning- build my equipment at 240V. am i correct in thinking this way? if so- i could build my amps even my pre-amp at 240V, but what about my DAC and CD player? i read that digital would benefit from balanced lines most! would building amps from 240V lines be beneficial to the sound. actually now that i think about it - it would, wouldn't it??
i'm so bright my daddy called me sun!
ok i'm not to bright am i? i was reading your post again and thought you might be meaning- build my equipment at 240V. am i correct in thinking this way? if so- i could build my amps even my pre-amp at 240V, but what about my DAC and CD player? i read that digital would benefit from balanced lines most! would building amps from 240V lines be beneficial to the sound. actually now that i think about it - it would, wouldn't it??
i'm so bright my daddy called me sun!
Not at all, the medical industry has been using balanced power for years. In Europe where 220/240 2 phase transformers are used they inherently benefit from Balanced power.
Most residential services are single phase, even the though you see two 120VAC branches at the panel, they are tapped off the same phase from the transformer. This means your Dryer and stove only see single phase 240VAC.
In the example Mr. Pass quotes your would not be able to get NEC, CUL or CSA compliance as it creates a hazardous potential to ground if a fault develops. That is if I understand his point correctly.
What I propose is taking both sides of a 240 feed, two Hots in Phase, and driving a 240 VAC transformer with dual 60VAC secondaires. This is possible with a dual input transformer from Plitron. You would them tie your neutral to ground to eliminate a PD ground short potential. Dont' forget to use a Double pole common breaker and hard wire a GFI between the two Hot Lines and Neutral Ground.
Just to clarify a previous point, the 13.6KV transformer on the local service poles is three phase 13.6KV per phase. If the Local Hydro company are using one AMP lines that would be 13.6KVA per phase, a 2 amp line would still be 13.6KV but would them be 27.2KVA. Which is coincidentally what the county or district lines carry. One you look at street hydro pole you will see 3 horizontal lines at the very top 27.2KV and 3 lines aligned vertically further down the pole 13.6 KV. The furthest cable down the pole is single phase 210 that runs from the 13.6KV transformers to your home.
Anthony
That's news to me. Out here in the wilds of California
my 240 volts is two live 120 volts in paraphase, and I
have not seen it any other way.
Is balanced AC line really supposed to be better? I surmise
that it would take a flawed transformer to reveal the
difference. Capacitive coupling between primary and
secondary seems to be the worst of the problem.
BTW, the very best (as in medical) transformers have an
electrostatic shield between primary and secondary.
This is really the way to go, especially for line level and
digital equipment. I picked up some EI type 2 KW line
isolation transformers surplus some years ago, and they
still are great, really improving the high frequency isolation
between primary and secondary.
my 240 volts is two live 120 volts in paraphase, and I
have not seen it any other way.
Is balanced AC line really supposed to be better? I surmise
that it would take a flawed transformer to reveal the
difference. Capacitive coupling between primary and
secondary seems to be the worst of the problem.
BTW, the very best (as in medical) transformers have an
electrostatic shield between primary and secondary.
This is really the way to go, especially for line level and
digital equipment. I picked up some EI type 2 KW line
isolation transformers surplus some years ago, and they
still are great, really improving the high frequency isolation
between primary and secondary.
Have you measured both branches on a dual trace scope and confirmed that the phases are at 120 Deg. seperation as the would be on a true 3 phase circuit? You have to remember the difference here Mr. Pass, a bifilar wound transformer gives you true 180 Deg. phase variance due to the nature of the windings. This is not to be confused with the 120 Deg phase difference in three or two phase circuits.
360 Deg divided by three phase is 120 Deg. You will never get noise summing to zero without a bifilar wound transformer.
Sorry to critisize you master, forgive me.
Anthony
Hello again Mr Pass, I agree with you about primary and secondary screening. I have reccomended the new IMIN Plitron transformers for balanced power due to thier low noise, low bandwidth, low inrush current capabilities. They are both shielded and screened.
I also agree the best applications for Balalnced AC are in Digital circuits like CD, DVD, LD, DACS, Video and what ever else you can think of.
BTW my reference to Europian equipment should stipulate that a bifilar wound transformer would still need to be used inside of the equipment.
One added note, Plitron claims thier new IMIN transformers are so good they have all but eleminated inter winding capacitance, which is what casuses a lot of the AC noise in first place.
My apologies for not clarifying the difference between how AC is delivered in 3 different phases and how bifilar windings regenerate AC 180 Deg out of phase, earlier in this discussion fourm.
Anthony
I also agree the best applications for Balalnced AC are in Digital circuits like CD, DVD, LD, DACS, Video and what ever else you can think of.
BTW my reference to Europian equipment should stipulate that a bifilar wound transformer would still need to be used inside of the equipment.
One added note, Plitron claims thier new IMIN transformers are so good they have all but eleminated inter winding capacitance, which is what casuses a lot of the AC noise in first place.
My apologies for not clarifying the difference between how AC is delivered in 3 different phases and how bifilar windings regenerate AC 180 Deg out of phase, earlier in this discussion fourm.
Anthony
Anthony;
I believe you & Nelson are in agreement, you just don't know it.
What Nelson described as 120V paraphase, you are calling
240V bifilar.
The transformer that feeds my house (and I assume, Nelson's)
could be described as:
Primary: 480 Volts (or 4160, etc...)
Secondary: 240 Volts center tapped
Two hots and one cold.
- herm
I believe you & Nelson are in agreement, you just don't know it.
What Nelson described as 120V paraphase, you are calling
240V bifilar.
The transformer that feeds my house (and I assume, Nelson's)
could be described as:
Primary: 480 Volts (or 4160, etc...)
Secondary: 240 Volts center tapped
Two hots and one cold.
- herm
It would not, 240VAC is what is delivered to residentail services. The service is delivered from a 13.6KV pole transformer in 3 Phase tap. What comes in to the service panel is electricity generated by a 3 pole turbine. As the turbine turns it's magnetic flux varies through 360 Deg of rotation as does the shaft and rotor. The armature has 3 coils usually connected to 3 pairs of contacts. As the brushes pass the contacts and conduct the induced EMF to the distribution network it does so at different rotation angles. These angles represented as a sine wave happen at 0 Deg/360 Deg, 120 Deg and 240 Deg.
When we talk about a transformer with Bifilar windings, we have one primary or two in series wound the same direction if it is a 120/240 transformer. Then you have your two secondaries which are interlaced and wound in precise opposite directions. This causes an EMF charge to be induced in one secondary at the exact time it is collapsing in the other, and vice versa.
Buy connecting the two secondaries in series and using the Centre tap as a reference ground, you can measure the full PD between them even though only one secondary is "On" at a time.
Now if you really want to live dangerously, you can connect the secondaries so that they are in exact opposition and when you measure the PD between the two you will read 0 VAC. Cool huh, this is because the sine waves are cancelling each other out, but if you measure to CT you will get half your expected voltage. This has no practical application in delivering AC as an ISO transformer . That said you could employ this method for a dual bridge DC supply where you completely 100% isolate power ground from chassis ground as your ground is now hot. The benefit, really clean and noisec free rectification as the bridges always see 0 VAC acroos the two secondaries. The drawback, instant electricution if there is a leak from power ground to chassis ground.
Is every one following along so far?
Anthony
Anthony,
Interesting read on the secondary.
Actually I was inquiring about the primary voltage that Herm had mentioned. I was just thinking that utilizing 480v for primary is unusual. Normally you have single phase 12kv or 6.9kv or some other voltage that goes to the primary side of the transfomer that are hanging on the pole or even pad mounted transformer and then the sec is 240/120v. I would think that to use 480v for primary would not be very effective - in terms of voltage drop. We are talking about residential homes here. Commercial could be different.
Interesting read on the secondary.
Actually I was inquiring about the primary voltage that Herm had mentioned. I was just thinking that utilizing 480v for primary is unusual. Normally you have single phase 12kv or 6.9kv or some other voltage that goes to the primary side of the transfomer that are hanging on the pole or even pad mounted transformer and then the sec is 240/120v. I would think that to use 480v for primary would not be very effective - in terms of voltage drop. We are talking about residential homes here. Commercial could be different.
This is my experience:I have two iso transformers rated at at 2.5KVA each. One is balanced laminated type the other other is what the maker said is an EI type. I prefer the sound of my system with them in line. The EI type sounds really amazing compared to normal AC lots more dynamics ,space,depth. This was with source components and Naim amps. However with my recently built Aleph 5 I am not so sure.The differences are not so dramatic. I think the bass is a little better when they are directly powered. Perhaps that's because they have huge PSUs compared to the Naim amps and the iso transformer is creating a bottleneck. Or maybe the huge Aleph PSUs are sucking most of the current that was going to the transport-DAC. I'll have to switch trafos and components around and see .
To clarify, in North America the primary of a Pole or Pad mounted transformer in a residential service is going to be 13.6KV. The secondary can be tapped down to 240 or 480 dpending on if the transformer is Centre tapped or not. These transformers are not bifilar wound. I believe I did mention this in my previous postings. My apologies if I was not clear.
The power output, that is KVA of the trransformer, depends on the current the power company allows to be drawn.
The primary voltages can vary as mentioned, 13.6KV is only a standard. Like all things there may be other standards.
Anthony
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