A wee bit of a mix up between what I said and what Aai said (no
'quotes' appeared to distinguish between the two).
the 9:23 message was from Aai but the
f=: 13 : '+/-: %>: +:i.y'
and the result corresponds to a specific immediate "calculator' solution that I
gave
]R100K=:+/0.5*%1+2*i.100000
I had not put it in the form that you present and I thank you for the
re-programming as a function-Gee-I can interpret it- I must be learning
something!!!.
As for an example of the Z-Bus method I gave a small example in a post at 6:12PM yesterday
I can give more examples but the practical ones I have on hand do involve
complex impedances.
Wiki gives little information so it appears that I will have to put together
some notes that I have - it appears that this approach is something known
mainly in power system analysis.
This is the best I have found so far on line and it is inadequate:
http://en.wikipedia.org/wiki/Impedance_parameters#The_Z-parameter_matrix
Inadequate because it assumes the typical application is for a 2-port network.
In computer methods for electric circuits, the handling of a nodal form is much easier
than the use of loop forms. This is due to the fact that the choice of equations comes
down to selecting one node as reference or ground and from there it is an automatic
procedure. For loop equations, one must make choices as to what are the loops to be
considered before forming the equations. So load flow solutions, one of the earliest
applications of computers to large networks (in or near 1964) were based on an admittance
network. Fault studies depended upon reducing a large network to a Thevenin/Norton model.
Inversion of this matrix gives the Z-bus matrix which presents both driving point and
mutual impedences between nodes. The "maxima' approach may be a way to 'build"
such a matrix without inversion of a large matrix (large in power systems can be in the
order of 100's to 1000's of nodes).
However, I will put together a few simple examples and dig up some references
or what I have in some notes on hand.
OK?
Don
On 09/01/2013 9:14 PM, Linda Alvord wrote:
This is a look at your earlier message at 9:23:43 AM.
f=: 13 : '+/-: %>: +:i.y'
f 100000
3.36911
5!:4 <'f'
-- [:
+- / --- +
│
--+ -- [:
│ +- -:
L-----+ -- [:
│ +- %
L----+ -- [:
│ +- >:
L----+ -- [:
L----+- +:
L- i.
A pretty tree. However you have left me with your 11:45 PM post unless you
provide some small numerical examples of the matrices and the inverses you
are looking for.
Linda
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Donald Kelly
Sent: Wednesday, January 09, 2013 11:45 PM
To: [email protected]
Subject: Re: [Jprogramming] xkcd 356
In my opinion, in most cses computer solutions are much esier using nodal
admittance methods once you select a node as a reference then it is very
easy to set up an admittance matrix yii is the sum of admittances connected
to node i from all nodes including the reference.
yij=yji =-sum of admittances between i and j. There is no row or column
related to the reference node.
Invert this matrix to get a Z-Bus matrix which is a generalized Thevenin
impedance The resultant zii terms are the driving point impedances (thevenin
impedance between i and reference.
for impedances between nodes i and j use zii+zjj -2zij which is the thevenin
impedance between i and j Zbus can be built in steps avoiding inversion of a
large matrix.
This method is shown or should be shown in modern power system texts as it
is very useful for fault analysis of large systems.
Don
----- Original Message -----
From: "Aai" < <mailto:[email protected]> [email protected]>
To: <mailto:[email protected]> [email protected]
Sent: Tuesday, January 8, 2013 9:23:43 AM
Subject: Re: [Jprogramming] xkcd 356
In fact this method is like measuring resistance with an okmmeter between
points A and B of the network.
FWIW here is my interpretation/translation of the Maxima code:
nbrs=: 1 3 5 7&{@,
swz=:0,.~0,.0,~0,]
resistornw=: 4 :0
'h w'=.x
'al bl'=. (+w&*)~/"1 y
d =.( <mailto:*=/~@i.@#> *=/~@i.@#) #&> ix=.,3 3 <@(<:#~0~:])@nbrs;. _3 swz
1+i.h,w r=. 1 al }zv=.0$~h*w A=. %. r (al)} d + _1:`[`]}&zv&>ix bl { A +/ .*
1 bl }zv
)
Your example is calculated like:
2 2 resistornw 0 0,:1 1
1
Or as David pointed out:
% +/ % +/"(1) 1 1 ,:1 1
1
On 08-01-13 17:24, Raul Miller wrote:
I'm a bit confused by the maxima solution. For example, A is both a
specific node and it's also a 10 by 10 matrix. Similar for B. I can
assume that the matrix values are something like potential
contribution from the named node. But... k looks like the 10 10 #.
of an index pair (with a bit of off-by-one since the maxima solution
is using 1 based indices) except it's used as an index into A and B.
And... so maybe A and B are really representing logically different
kinds of data in different parts of their structure? But what is the
logical structure then.
... anyways, the purpose of some of this code is not clear to me.
--
Met vriendelijke groet,
@@i = Arie Groeneveld
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