What is the significance of this symbol?

[That Man]

1

 

[gar]

190829-2418 EDT

My guess:

I believe the right had winding is the reverse of all the others, and is half the turns of the windings between the other taps. Thus, a means to get more taps without having to create physical taps.

I believe that the drawing is very descriptive of my guess. Note it is drawn as 1 turn vs 2 turns between the other taps, and an effort was made to indicate a reversed winding.

.

 

[GoldDigger]

190829-2418 EDT

My guess:

I believe the right had winding is the reverse of all the others, and is half the turns of the windings between the other taps. Thus, a means to get more taps without having to create physical taps.

I believe that the drawing is very descriptive of my guess. Note it is drawn as 1 turn vs 2 turns between the other taps, and an effort was made to indicate a reversed winding.

.

That would be true if you moved one tap between X4 and X5 and moved the other tap to X1, X2, or X3. That way you get half step ratios between what you get using just X1,through X4 instead of just one more ratio from addition of X5. Is this actually done? I do not know.

Did the OP actually confirm that the turns number between X4 and X5 is the same as all the other steps or is he just assuming that?

 

[That Man]

1

 

[That Man]

Clearly, the ratios aren't as regular as I thought. However, they still seem purely addative.

 

[gar]

190830-0711 EDT

My guess about the schematic was clearly wrong.

With the new information the schematic alone is clearly misleading.

The coils are 4, 8, 3, and 5. With the table information are clearly all additive.

4+8 = 12,
8+3 = 11,
and 3+5 = 8 is redundant with the single 8 coil, and of no use

4+8+3 = 15,
8+3+5 = 16

4+8+3+5 = 20

Thus, 4+2+2+1 = 9 different values. This corresponds with the table count.

.

 

[junkhound]

The symbol indicates a bushing type CT (e/g, incorporated into case of equipment vs stand alone). (per IEEE 1975 standard iirc)
The winding from 1-4 is a completely distributed winding, the 4-5 winding is electrically continuous with 1-4 but on a different section of the core. Very slight effect on accuracy.

 

[gar]

190830-0911 EDT

junkhound:

Can you explain the logic of the schematic?

Also why would X4-X5 be wound on only a portion of the toroid? I would think that each coil (that is between taps) would be wound uniformly around the circumference of the toroid to provide best coupling.

None of the internet sites I found on bushing type CTs showed a diagram with multiple taps.

Why would the 100 to 1 ratio be singled out to be wound differently?

.

 

[gar]

190830-1009 EDT

Looking at the schematic of post 1 and redrawing it with the coil X1-X4 completed at X4 as a mirror image of X1, then X1-X4 would look like a single winding. Next if X4-X5 was drawn as X1 starts with a completion as I suggest for X4, then X4-X5 would look like a separate coil, but connected to X1-X4. Now I would not to be led to think there was a phase reversal.

.

 

[LarryFine]

To me, it suggests that there is a (removable?) jumper between X3-X4 and X4-X5

 

[Tony S]

Have a look for “Brentford” transformers.

You mention Asea, they’re normally for high frequency induction furnaces.

I’ve only worked on an Indutotherm low frequency furnace. I redesigned the control system, it became the bain of my life. Every time it burped, my phone rang!

 

[synchro]

The symbol indicates a bushing type CT (e/g, incorporated into case of equipment vs stand alone). (per IEEE 1975 standard iirc)

Yes, as shown on the following page of IEEE standard:

https://www.google.com/url?sa=t&sour...JDXqnK#page=50

 

[gar]

190830-1502 EDT

To go from 6.4.19 of https://www.noao.edu/ets/Mechanical/Policies/ANSI Y32.2-1975.pdf and say exactly how the transformer is wound is a real stretch.

.

 

[That Man]

So, bushing type CT it is. Thank you all for your comments and thank you Junkhound for providing a definitive reference. I knew the forum would know.

 

[Hv&Lv]

Bushing type CTs, as stated. Going back in Wye for the CTs I assume for 787? and/or 751s? The compensation values are weird on the SELs. It’s easy to get a double negative in them depending on system rotation. Still works, but...
as long as A is on H1, it’s all good.