Tom says:
>What is forgotten is this. Inrush occurs over several AC
>cycles, not just a fraction of one cycle.
>Starting at zero almost guaranties maximum inrush damage to
>components, because the entire first quarter cycle of ramp up is
>available every time for surge, as well as the start of the next
>half cycle, and so on.
>What you really want to do is slowly start the supplies, and remove
>limiting after all the components have had a change to charge (or
>filaments to reach higher temperatures.
>
>Inrush is a duration problem over a few seconds, it is absolutely not
>a 1/240th of a second spike problem cured by zero crossing turn on.
I hadn't realised quite what Dave meant by
>>Sounds like a nice way to eliminate the mechanical relay with current
>> limit resistor for surge protection.
until I read Tom's comment.
I agree 100% with Tom on this. (I know, makes a change for me to 100%
agree with anyone). I guess the best would be the old fashioned motor
starter, where you progressively shorted out series resistance, and the
handle was held by the 'no-volt' trip against a
spring....................but not for anyone wanting an 'instant on '
amp!
73
Peter G3RZP
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