Talk:Symmetrical components

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by virute of their being decupled,symmetric components are releted to each other by the fosterque matrix.the matrix contains the expression for the three components in terms of "i",which is in fact a representation of the imaginary operator in mathematics. however,in this case the multiplication of a vector by the quantity shifts its phase by 120,and not 90 degrees as would have been expected to happen. the positive phase sequence always exists in a net work and in a multi phase system,the positive phase sequence isn the only sequence when a conditiuon of imbalance or fault occurs the negetive phase and the zero phase sequence arise. the negetive phase sequence is exactly in the opposite direction to the positive sequence.typically this can be formed by interchanging any two of the three terminals in an electrical device(with three phase connections).since the negetive phase sequence is oppposite in orientation,for an electrical load supplied with a supply the generated emf is exactly opposite and hence the representaion contains no emf source. the positive phase sequence,however is represented as a power source driving all the impedences/loads in the circuit. the zero sequence network comprises of three 'in phase components' typically theyu do not cause any torques i machines at5 standstill,but on rotation their equvalent torques may not result to zero.they chiefly arise during grond associated faluts.

[edit] Moved from article

 I have a difficulty with the description of the postive, neagtive and zero sequence components.  My understanding is that these terms are used to describe the sequence with which they rotate.  This is not the same as their direction of rotation.

Thus the postive sequence set would sequence in the (conventional) order of RYB. The negative sequence set in the order RBY, whilst the zero sequence set have no sequence, ie they are in phase with each other.

I suggest that the author(s) of this article might like to review their contribution in this regard.

Ian Grant Whitianga NZ

I moved this commentary from the article. Since there's little to identify an individual phase, I don't know that a definitive decision can be made between two sets of phasors in the same phase sequence and opposite rotation, vs. two sets with the same rotation and opposing phase sequence. Is the distinction even meaningful? Physically I know that negative phase sequence currents give rise to motor torques that oppose the positive sequence, so to me it seems appealing to call them opposite rotation. --Wtshymanski 17:59, 25 August 2006 (UTC)

As stated in Blackburn (Para. 3.2.2, see article references), the phasor set always rotates counterclockwise (angle increasing) according to normal mathematical convention. The positive- and negative-sequence space vectors rotate in opposite directions, but these should not be confused with phasors. The phase sequence or rotation is the order in which the phasors pass the axis with increasing time (the sequence of maximum voltages). This means that for normal a-b-c sequence, the sequence is from a clockwise to b, then clockwise to c. As a machine designer, I usually visualize the space vectors.

Allen Windhorn Kasota, Minn. USA