[Amps] Re: Amps digest, Vol 1 #357 - 15 msgs/INRUSH CURRENT PROTECTION

[Dan Fitch]

I haven't tried the idea yet - just relaying what was in the old ARRL
Handbook.  I did grab a 60W lamp in the shop just now and found the cold
resistance was around 20 ohms.  The hot resistance should be around 240
ohms, using 120 volts RMS and 60W.  I believe the 20-ohm figure for the cold
lamp is considerably larger than the initial resistance looking into the
primary of the transformer.

It would be interesting to look at the surge current, with and without a
lamp in the primary, by measuring the voltage across a small resistance
placed in series with the capacitor bank.  A single trace o-scope could be
used if the grounded side of the capacitor bank could be disconnected from
ground and a resistor (1 ohm or less) inserted.

By the way, Guillermo is correct.  The 60W (240 ohm) lamp draws about 1/2
amp when hot - the inrush is momentarily about 6 amps when it is cold.

73' Dan, KB4L


-----Original Message-----
From: amps-admin@contesting.com [mailto:amps-admin@contesting.com]On Behalf
Of Guillermo
Sent: Thursday, October 31, 2002 9:20 PM
To: Amplificadores Lineales
Subject: Re: [Amps] Re: Amps digest, Vol 1 #357 - 15 msgs/INRUSH CURRENT
PROTECTION

    Is this light bulbe system effective?, because at first bulbe's filament
exhibits a very low resistance, increasing then as it gets hot. At least for
a
very short time, I figure this will allow a high current peak initially.

Best regards
Guillermo - LU8EYW.