Thanks for all the input on the ps problem so far. For a little more
background info, the amp I am using works fine with a smaller ps
(4kv 1 amp). I built the new ps inorder to obtain higer plate voltage
and less grid current.
The amp is ok and the radio is ok. I am not going to use 2 amps
at 5kv. I am just looking for maximum of 3kw out (It should do that
anyway) and better efficiency. This powersupply will provide
plenty of juice. I have seen 1 amp continuous with no problem.
I will restate again that I am using a transformer that was designed
for a choke input, but I am not using one. The email below is addressing
what I believe to be the root of the problem. When I key the amp,it has
about 400 ma of idleing current (no drive). If I send a cw dit or dah,
sometimes but not always the breaker will trip. Sometimes you hear that
thud like when turning on a larger 12 volt power supply and the switch is
flipped at the peak of the ac cycle. And worst case the breaker flips on
just a couple quick dits. WIth the smaller power supply I can drive the
amp to 1.2 kw. With the bigger power supply the breaker will trip when
the thud occurrs. I have not exceeded 800 watts yet with the new ps.
So I am still looking for a solution of sorts. Please read Bill's
comments
below. I am using stepstart which requires about 10 seconds (timer).
Subject:
Re: [Amps] PS project
From:
Bill Fuqua <wlfuqu00@uky.edu>
To: <amps@contesting.com>
Date:
Thu, 10 Apr 2003 14:21:26 -0400
To:
Lynn <no9z@soltec.net>
The problem is that the power transformer should be used with a larger
breaker or
one that will respond slower. You may need to start up thru a resistor
and then
short out the resistor ( only a fraction of a second is required).
If you apply line voltage to the primary about every other time the
breaker kicks out
even with the secondary open you are getting a current surge due to the
core being magnetized when the
power was previously removed. If you switch in the power say the
positive cycle and it was switched out
on the negative half of the cycle everything would be just fine. But if
you switch in the transformer on the
same cycle that it was turned off on the circuit breaker will open. This
is because the transformer core is magnetized in the same direction that
current flowing thru the primary is trying to magnetize it so there is
no flux change. Thus for a sort instant the inductance of the primary
drops to practically nothing.
73
Bill wa4lav
At 01:11 PM 4/10/2003 -0500, you wrote:
> Hello all...... I need a little advice on this powersupply project.
>
> I have almost completed a nice 5000 v 2amp supply using a large
> Wilcox transformer with a capacitive filter. 50uf at 7kv.
>
> I found out after construction that the Wilcox transformer requires
> a choke input. The circuit breaker trips (25amp) when sending a
> cw signal from the radio (occassionaly). I believe the output
> impedence
> of the power supply is too low, thus causing excessive current . It
> appears this happens when the ac cycle is at its peak.
>
> Is there a solution to this problem where I can still retain the 5kv?
>
> I understand that if a choke is installed in the b+ the output will be
> .9 of the rectified ac instead of 1.3 times the ac supply volts.
>
> Ideas?
>
> Lynn NO9Z
>
>
>
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