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jaus tail
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Homework Statement
Homework Equations
Dot is A2.
A1-A2 of star is in phase with A1-A2 of delta
The Attempt at a Solution
I'm getting answer as Y-Delta - 1. Assuming Y is HV.
How is C right answer?
old jimSatire III
By John Donne
Kind pity chokes my spleen; brave scorn forbids
Those tears to issue which swell my eyelids;
I must not laugh, nor weep sins and be wise;
Can railing, then, cure these worn maladies?...
Yes. The 1, 5, 7 and 11 refer to the hour hand on a clock. 6 and 0, or should that be 12, also happen. There are 12 hours on the clock face so each hour is 30° degrees. And so here I am trying to forget that the sun appears to move 15° per hour in the sky. I have been trying to sort out the convention but I get phasor angles that are the opposite of what I need.jim hardy said:I've never encountered that kind of notation before. Do the odd numbers 1 5 7 11 refer to phase shift somehow?
All i did was pay close attention to labeling and add them head to tail , as we were taught decades ago.Baluncore said:You got it right in your paint, the diagram you cut and posted got it wrong. Why is that so difficult?
jaus tail said:It's always difficult to think that book may be wrong.
Book has only drawn YD1 and YD11 and not labelled anything. just dots. I found labels on google.jim hardy said:Where does book put A1 and A2 on primary and secondary ? Same place you did, or A1 on left both primary and secondary ? That'd reverse the secondary connections as @Baluncore suggested.
Gotta be rigorous in labeling. If textbook didn't label with rigor it's student's choice and a textbook error
Stick with the basics.
I am not yet sure of the correct process to follow when reading the clock.jaus tail said:Is this answer YD1 or YD7?
jaus tail said:Is this right?
Direction of phasor is determined by dot and which ends of the winding you assigned as FROM & TO... that is, where you wrote your a1 and a2jaus tail said:When will the other winding phasor be upwards and when will it be downwards? As in where should dot be?
jaus tail said:@jim hardy
As per your rules will the two diagrams below have different clocks / phase shifts?
View attachment 218935
jim hardy said:Great question .
Clearly they'll behave the same when measured at their dotted ends. But -- As "Author In Charge of the drawing" you're free to assign your labels this way, Not that you would but somebody else might.
View attachment 218946
Left one, secondary Vab is voltage across A winding. Right one, it's voltage across B winding..
Label carefully.
.
jaus tail said:5) Use Dots for
----Now if in primary current is entering winding from A2 terminal and in secondary current is leaving winding from a2 (figure out from dots), then A1-A2 and a1-a2 are in phase.
----But if in primary current is entering winding from A2 terminal and in secondary also current is entering winding from a2, then A1-A2 and a1-a2 are 180 degree out of phase.
The clock notation in star-delta 3-phase transformers is used to represent the relative phase angles between the three phases. It helps in visualizing the phase relationship and simplifying calculations for power systems analysis.
2.The clock notation is used to determine the phase sequence by observing the direction of rotation of the phasor diagram. If the phasors rotate in a clockwise direction, the phase sequence is RYB (red, yellow, blue). If they rotate in a counterclockwise direction, the sequence is RBY (red, blue, yellow).
3.The advantage of using clock notation is that it provides a more intuitive and visual representation of the phase angles and phase sequence. It also simplifies calculations and analysis of power systems, especially in cases where there are multiple transformers connected in parallel.
4.In transformer connections with neutral terminals, the clock notation is used to represent the phase angles between the neutral and the three phases. The neutral is represented by the center of the clock, with phase angles of 0, 120, and 240 degrees for phases R, Y, and B respectively.
5.Yes, clock notation can be used for other types of 3-phase transformers, such as wye-wye, delta-delta, and wye-delta. It is a universal notation that can be applied to any three-phase system to represent phase angles and sequence.