Ian,
The first 1 to 5 cycles is the worst part of the surge, but from tests that was
run by a ham on this mailer, the transformer didn't settle down until 30 to 40
cycles. This was captured on a storage scope and I have the results here
somewhere saved as a jpeg photo. Anyhow, a 1/2 second delay is about all that's
needed on the step start. I'd say they used this heater cone over its greater
power rating than would be a 25 watt or so resistor. If anyone is interested in
the photo, I'll try to dig it up and e-mail it.
Best,
Will
*********** REPLY SEPARATOR ***********
On 9/18/06 at 7:36 AM Ian White GM3SEK wrote:
>Bob Maser wrote:
>>Can anyone tell me what good is it to have one of those cone heaters in
>>series with the primary of the plate transformer? When the cone heater is
>>in the circuit, the secondary voltage is 2800VDC and when it is shorted
>out,
>>it is 3000VDC. Hardly seems worth the effort. The cold resistance of the
>>cone is ±30 ohms.
>
>All the good happened in the first two or three mains cycles, when the
>resistor limited the surge current to less than 8A (<240V / 30 ohms).
>
>By the time you can see anything on a meter, the surge is over and the
>resistor can be switched out.
>
>
>--
>73 from Ian GM3SEK
>
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