Inserting coupled inductors into NG-Spice’s netlists graphically.

I have spent quite a few postings, describing how the Open-Source circuit simulation programs “NG-Spice”, belonging to the “gEDA” suite, can be used. And one of the facts about them which I’ve recognized, is that they essentially come as three programs: The (non-GUI) engine which simulates Netlists; ‘gschem’, a graphical program which allows schematics and custom symbols to be edited; a third (GUI-based) program, ‘GSpiceUI’, that can import the schematic and export the netlist of a simulation to be run, as well as run the simulations.

What the first two programs do, isn’t always well-matched. ‘gschem’ can create schematics, with no regard for the fact that the Spice engine can’t simulate all the components.

But, One capability which NG-Spice has at the level of Netlists is, to simulate “coupled inductors”, which are denoted by a ‘RefDes’ which begins with the letter ‘K’.

Why is this potentially useful? Because, if the user simply puts the standard, library transformer, what NG-Spice will simulate, is a perfect transformer, which behaves as well at 60Hz, as it does at 60MHz. The user would have no way to specify any of that transformer’s parameters, then. It’s often more useful to simulate components, with built-in parasitic flaws, such as, coupling constants that are 0.99 or 0.9 instead of 1.0…

It would be nice, just to be able to drop such a coupling into a ‘gschem’ schematic, and have ‘GSpiceUI’ create its simulation ‘the easy way, via the GUI’.

Well, that can be prepared. And, the way to prepare it is, using ‘gschem’ in order to define a custom symbol…

 

coupled-inductors-1

 

(Updated 6/09/2021, 16h35… )

Continue reading Inserting coupled inductors into NG-Spice’s netlists graphically.

Reducing Induction Effects, Counter-EMF, and Stray Voltages in Low-Voltage Communication Wires.

One of the observations which amaze older people like me, is how high the frequencies have become, at which even household appliances such as USB Cables can communicate. In my youth and young adulthood, such things would not have been considered possible. And the surprise which this progress brings, comes more strongly to older people, who actually did know about Electronics.

There is a basic enemy to allowing communication at high speeds: Plain wire has linear inductance, which becomes significant at the higher speeds.

There is a basic methodology to reducing the unwanted effect: Actual signal-wires are often accompanied by a shield wire, which needs to be grounded or connected to zero, at both ends of a wire bundle.

The concept is quite simple. This shield wire acts as a kind of secondary winding, to a virtual transformer, of which the signal wire would be the primary winding. Whatever counter-EMF the signal wire would produce, would also need to exist along the length of the shield wire. But because the shield wire is grounded at both ends, the counter-EMF which the signal wire can produce is also greatly reduced, in comparison with what one would obtain, if the signal wire existed by itself. When current flows in one direction through the signal-wire, current also flows in the opposite direction through the shield wire. If that current could not flow, then the full linear inductance of the signal wire would seem to exist. Otherwise, not so.

Now I suppose that it would be nice if overhead wires that stretch geographical distances, could also be shielded as easily. But one fact which is highly disappointing is, that shielding / elimination of stray-power problems, is highly lacking in many practical situations. More specifically, power lines may often only seem to have real phase wires, but no neutral wire that runs parallel. Instead, what some Engineers do, is simply to sink a grounding electrode into the earth, at the receiving end of such an arrangement.

The problem with that is the fact, that Earth is not a perfect conductor, and was also never ‘meant to’ participate in Humans’ high-voltage circuitry.

(Updated 3/12/2019, 15h20 … )

Continue reading Reducing Induction Effects, Counter-EMF, and Stray Voltages in Low-Voltage Communication Wires.