Anti-parallel configurations (fwd)

[<sroys@xxxxxxxxxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 19 Nov 2004 18:54:46 -0600
From: Dr. Resonance <resonance@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Anti-parallel configurations



Anti-parallel configuration means (example) soldering 3 diodes in series.
Then solder 3 more diodes in series.  Then comes the parallel part:  attach
the anode end from one to the cathode end on the other string.  Then do the
same on the other end.

We use this to protect sensitive uA meters that are monitoring HV.  If the
meter has an open it will go to HV and start arcing --- bad in a control
panel.  By using the anti-parallel string across the meter terminals, then
the normal current is monitored by the meter while the anti-parallel diode
string provides a max rise of around 2.1 Volts (0.7 Volts for each 1N4007
diode) if the meter series wiring internally should become an "open".

Like this:

                [--------C--A-------------C--A-----------C--A------]

[                                                                  ]
  ------------[                                                             
     ]--------------------

[                                                                  ]
                [--------A--C-------------A--C------------A--C-----]

Each C--A or A--C represents cathode--anode, ie, a single 1N4007 diode.

This allows you to connect a DC uA meter to the long series high Ohmic
resistor and connect the opposite end thru the meter to ground.  If any open
develops in the meter the current then starts to flow thru the next lowest
resistance path which is the anti-parallel diodes.  They tend to hold the
max potential to 2.1 Volts as opposed to a spacing which allows arcing and
eventually actually physically burns the meter up.  Or, worse yet, it
silently smolders away after you leave the lab and burns the lab down in the
middle of the night!

With metering, common practice is to use 5-6 diodes in each string.

Anti-parallel circuits are also commonly used for high power ignitron
switching systems.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
>



> >Subject: 'Anti-parallel' ??
>
> >I threw this out as part of a larger issue a few days ago and I wanted to
> >see if anyone would be willing to hazard a guess as to what the term
> >'anti-parallel' means?  The context is almost always in the wiring of 2
> >transformer primaries in parallel in preparation for putting the
> >secondaries in series.
>
>
> I wired my two H&R transformers together this way. I was told that wiring
> the primaries in parallel and the secondaries in series was called
> 'anti-parallel'.
>
> Alan Jones
> KI4ATV
>
>
>