Hal and everyone,
Personally, I always used a 1 second delay, but the transformer wasn't as large
as the one that I think you have, if it's the one you showed me photos of.
There's other factors like the capacitance in the filter and the current surge
added from it. When I say waiting until one settles down takes into account for
the current to normalize which sure helps the transformers windings. Most
everyone uses around 1/2 second though by seeing what's used on this reflector
and on the available kits. I still personally prefer 1 second though on my past
projects, I can sure wait that long for the transformer to start drawing a
normal current. Really, to do it right, one should watch the surge pulse time
with a storage scope using a shunt in the line lead. If you don't have a
storage scope, you can pick up a good used external storage adapter off ebay
pretty cheap. B&K made a decent one as I'm not sure of any other brands off the
top of my head. It saves the incoming signal to memory then you can re-play it
on the CRT. It has both voltage and time base controls just like a scope. It
mounts in the test lead line between the probe and the scope. A storage scope
works different than this though, unless it's some of the newer stuff.
In Hals case, he could have very well needed a longer delay until everything
normalized. The main surge current of the transformer though can be way larger
than the operating current. The cycles start as a sharp high spike and form a
bell curve as the time in cycles goes on growing weaker until it normalizes to
the operating current. You then have to add the capacitor charging current, and
the load current to this spike caused by the transformer itself. The larger the
transformer, the worse this is since the resistance of the primary drops with
increased size in volt amperes, and the stiffer the supply thus a better ripple
rating, the more it is.
Best,
Will
*********** REPLY SEPARATOR ***********
On 9/19/06 at 4:05 PM Harold Mandel wrote:
>There are all sorts of delay relays available in the commercial electrical
>market.
>
>All elevators use these plug-in devices. The modern ones run on a.c. or
>D.C,
>and
>from 24 to 240 volts, all on the same terminals with no jumper changes.
>
>Most of them are made to fit octal tube sockets, and some of the newer ones
>fit
>DIN rails.
>
>These come with adjustable settings on the top. Some come with
>range settings that can go from Ø to 1 second, 1 - 10 seconds and
>also in minutes and hours.
>
>Looking at the D.C. anode voltmeter swing up on my power supplies
>1/2 second does not leave time for everything to normalize and the
>delays were set to five seconds. The voltmeters are then stable before the
>contactors release.
>
> Hal Mandel
>W4HBM
>
>-----Original Message-----
>From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>Behalf Of Phil Clements
>Sent: Tuesday, September 19, 2006 3:07 PM
>To: amps@contesting.com
>Subject: Re: [Amps] Step Start on a 3KA Amp
>
>
>>
>> Sounds a bit primitive - no wonder it needs that big resistor! With so
>> many well-known ways to make a completely automatic step-start, it seems
>> a really strange decision to use a manual switch and leave the whole
>> thing wide open to operator error.
>
>Many of the Henry amplifiers were sold to Government and Commercial users.
>They were in U.S. Embassies all over the world. Henry assumed that the
>operators would read and adhere to the manuals. If you have not operated
>one
>of the Henrys, it may seem primitive to you, but in practice, one just
>rotates the mains switch from off to on in a normal manner. The travel in
>the rotary switch from off to its final position of on gives the proper
>amount of time for the step-start to function properly. The operator did
>not
>have to give this any thought...just turn it on! It worked well for decades
>until the amps fell into the hands of folks who did not read the
>instructions, or didn't get a manual with the radio. This "primitive"
>circuit has only one moving part; the very robust a.c. mains switch. If one
>did fry the cone heater, it could be replaced as easy as a light bulb.
>Sometimes K.I.S.S. is a good route to take if you are in primitive
>territory.
>
>(((73)))
>Phil Clements, K5PC
>
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|