[Amps] soft start circuits

[R.Measures]

>PAUL HEWITT wrote:
>>
>>
>>> -----Original Message-----
>>> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
>>> Behalf Of David Lisney
>>> Sent: Thursday, January 08, 2004 9:05 AM
>
>>>one minor bug is that the lightly loaded solid
>>> state relay has once operated by itself, probably due to a mains
>>> transient, and the power supply has powered up by itself, hardly
>>> a major concern in a fully enclosed low voltage power supply but
>>> not something you'd want to trust entirely. This glitch has only
>>> occurred twice in maybe 10 years but still not acceptable for a
>>> high voltage supply.
>>>
>>>
>>The SSR manufacturers recommend MOV's at the line side terminal to avoid
>>DV/DT turn-on.
>
>Even better would be a mains filter, then the master mains switch, and 
>then the MOVs on the SSR.
>
>The filter protects the whole amp, including the transformer and 
>rectifiers, from incoming mains spikes. 

**  The HV filter capacitor in the anode-supply protects against spikes 
provided that FWB or FWD rectification is employed.  

>The spikes are attenuated and 
>stretched enough that they may not affect the SSRs anyway, and the MOVs 
>are a good backup. Since MOVs can be 'worn out' by having to handle too 
>many transients, it's best to connect them downstream of the master 
>mains switch, so they only see mains voltage when the amp is actually 
>switched on.

**  Good MOVs have  straps for leads instead of wires. 

>...