>Guess value of surge limiting resistor is an empirical question, start with
>high value, observe response on scope....
** Starting with a resistance that will limit current to the
circuit-breaker rating will get one in the ballpark.
>Thought : use of incandescent lamp as resistor. Understand that tungsten
>filament resistance increases with current flow, but I may be wrong on this.
** You are correct, Barry
>
>----- Original Message -----
>From: "Marcinio Afonso Stabile" <marcinio@terra.com.br>
>To: <amps@contesting.com>
>Sent: Wednesday, January 07, 2004 9:05 PM
>Subject: Re: [Amps] Step start resistors
>
>
>> Hi Peter!
>>
>> I am using thermistors as inrush current limiters, for a variable
>frequency
>> AC drives, in a pre-charge system, to limit the charging current on the DC
>> bus capacitors. More information at Ametherm web site:
>>
>> http://www.ametherm.com/Inrush_Current/welcome.html
>>
>> I hope it could be a usefull idea. Here in Brazil, PY2WM (De Marco) tested
>> this solution on the rebuilt of your Delta 1000 linear amplifier (4 x
>811A)
>> with sucess, using a thermistor removed from a surplus PC power supply.
>See
>> the description (in portuguese only, sorry!) at:
>>
>> http://geocities.yahoo.com.br/jkdemarco/Delta1000/Delta1000.htm
>>
>> 73!
>>
>> Marcinio Afonso Stabile - ZZ2TWT
>> Jaboticabal - SP - Brazil
>> http://www.stabile.eng.br/tubes
>>
>> ----- Original Message -----
>> From: <peter.chadwick@Zarlink.Com>
>> To: <amps@contesting.com>; <amps-bounces@contesting.com>
>> Sent: Monday, January 05, 2004 8:41 AM
>> Subject: [Amps] Step start resistors
>>
>>
>> >
>> > Any ideas on what values to use for step start resistors? In the past,
>> I've
>> > tended to choose a value from the available stock - something like 50
>> ohms,
>> > 100 watts, which limits the surge current to just over 4 amps. I expect
>> > that a value such that the current won't exceed the full load primary
>> > current of the transformer is probably best, but any suggestions?
>> >
>> > (I'll probably still use what's available in my stock of vitreous
>> enamelled
>> > wirewound resistors about 10 inches long and an 1 inch in diameter,
>> > though!)
>> >
>> > 73
>> >
>> > Peter G3RZP
>> >
>> >
>>
>>
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>>
>
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