[Amps] Step start resistors, another solution

[Paul Christensen, Esq.]

> Another way to limit the surge is to use Crossing Relays.   I use two 40
amp
> crossing relays on a 4000 volt/2 amp HV supply, and it works great.
These
> work by not completing the circuit until the amp draw would be zero during
> the 60 cycle phasing.

I've seen solid-state zero-crossing switches used for this purpose.
However, maximum current is achieved in just 90-degrees at 60 Hz (assuming
no zero reactance in the circuit).  This equates to only 4 ms.   It this
sufficiently enough time to limit filament current in-rush, especially with
directly-heated cathodes?

-Paul, W9AC