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RE: saturable reactor vs choke

Original poster: "Jack King" <ekklekktikk@xxxxxxxxxxx>


Greetings,
I have seen the SPANG S-Rs you speak of - I looked at buying all 6 of theml, but, seeing that they were factory parallell wired (magnetically inversely, so as not to induce any appreciable v on the center ctrl winding) that, I figured I would have far too much starting inductance to make this useable with just a 240 v input....now if they were set-up in a way were they were series connected for 440 and parallel for 240, that MAY have made them practical (for me anyway)....I also looked @ de-winding the outer stacks on these to give lower initial inductance - as I want a target start current on the HV transformer of around 100 ma (lower than that is waste for me) and able to glide up through about 1600 ma. I am already able to do this with MUCH smaller manageable size/weight cores.
I am curious to see how this beast works out for you. One other observation I have made using "oversized" cores like this for practical purposes, is that they exhibit MASSIVE inrush current overshoout for about 1 cycle, but that's ample enough to pop a 100 amp main breaker - this seems to be luck of the draw as to "where" in the cycle everything turns on....Also you want to make absolutely certain that the FIRST thing to switch off is the DC control and it should be the last thing to turn on...even a trickle of dc can pre-magnetize the core and cause massive inrush current - like it's not even in circuit with your pig at all.... 

Cheers,

Jack King


From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: RE: saturable reactor vs choke
Date: Sun, 16 Apr 2006 20:54:50 -0600

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hi Gerry, David, et al,

I have in industrial SR 20KVA in the back of my truck waiting for better
weather. The dc action in one direction is counter acted by joining two
opposed winding for the center DC control winding. Or that is the way I have
seen them drawn and explained on the Inet anyway. The schematic on mine is
not drawn that way which concerns me. I hope I don't need two :-^) check
this one...
http://teslabalast.blogspot.com/2006/03/large-suturable-inductive-balast-for
.html 375lbs!

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Sunday, April 16, 2006 9:34 AM
To: tesla@xxxxxxxxxx
Subject: Re: saturable reactor vs choke

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi David,

The BH curve looks like the BI curve (since H and I are related).  B
(y axis) and H (x axis). This is the curve with hysteresis and has a
sloped region when H goes from negative to positive (B is still
negative when H crosses 0) and another sloped region when H goes from
positive to negative (B is still positive when H crosses 0 so doesnt
follow the same path, hence the hysteresis).  as H gets too large,
the B flattens out showing saturation.  I'm trying to contrast two
materials, one where saturation occurs abruptly and another where the
slope of the curve gradually flattens out (soft knee).  If the knee
is abrupt does the current go to infinity when the saturation point
is reached or do things still behave rationally.  Also, it seems like
saturation aided by the DC current will occur in one AC direction
only.  Not sure what the implications are.

Gerry R

>Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
>Gerry,
>
>I'm not too sure of exactly what your asking but I'm assuming that
>you are making referance to the "bell
>curve" or "J curve", actually, that would represent the magnetic
>saturation range of the reactor's core on an x-y graphic? From what
>little personal experience that I've had with SRs, by gradually
>increasing the input DC voltage (usually something like 0 - 90 VDC
>at a few amps), you will proportionately increase the allowed
>current flow to the source load through the main coil. I BELIEVE
>once full saturation is achieved (90 VDC input to the control
>winding) then the main coil behaves almost like a short circuit.
>Conversely, with a zero volt DC input to the control coil, the main
>work coil will have maxi-
>mum inductance and L reactance to the main AC volt-
>age and will allow a relatively small current flow, irreagardless
>of the load, even if it's a short circuit.
>
>David
>
>
>----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
>To: <tesla@xxxxxxxxxx>
>Sent: Friday, April 14, 2006 1:44 PM
>Subject: Re: saturable reactor vs choke
>
>
>>Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>>Hi David,
>>A few questions:
>>If one has a saturable reactor and the BH curve is sorta ideal with
>>respect to the knee ( ie: it has constant slope until it saturates
>>and then the curve precisely flattens out), I'm wondering what
>>happens when this knee is reached.
>>Does the current scream very high or is there a smooth transition
>>to larger current as the saturation point is changed??
>>Does a saturable reactor require a soft knee??
>>Gerry R.
>>
>>>Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>>>
>>>With a "saturable reactor" (SR), in addtion to the "working"
>>>inductive coil, there is also a "control coil" of usually many
>>>more turns of smaller guage wire than the main "working"
>>>coil. A relatively low, variable DC voltage is introduced into the
>>>control coil to control the magnetic saturation of the iron
>>>core so as to control the current flow through the main
>>>working coil. This allows infinite range of the current that's
>>>allowed to flow through the main working coil, irregardless
>>>of the source load.
>>>
>>>David Rieben
>
>
>