[Amps] Zero Crossing circuit

[Will Matney]

Dick,

I see it like this following example. Suppose there were two of the same 
model cars setting at a stop light. Both being the same year, and same 
amount of miles. Suppose a lil ol lady was driving car A and Dale Jr. 
was driving car B. When the lil ol lady in car A starts out from the 
light, she gradually steps on the gas, bringing the car up to speed. 
Then, Dale Jr. in car B, when the light changes, floors the gas, and 
brings the car up to speed. They run both these cars this way for some 
time, but bringing each up to the same speed each time. The only 
difference being the driving method (acceleration). Which car would fail 
first? I would imagine car B would with Dale Jr. driving it due to the 
stresses and strains induced by the sudden jolt of acceleration. To me, 
there would be no difference between this, a step start PSU and one 
without it. The only way car B could stand it is if it were made to be 
ran this way.

A better example would be in a hydraulic circuit. One where the pressure 
slowly comes up and one where the pressure suddenly appears. The one 
which suddenly appears causes hammering. Hammering in a hydraulic 
circuit causes seal leakage (same as electrical leakage), and eventually 
seal failure (a short in electrical terms). This is caused by the sudden 
impact on the seals over time, or a jolt to the circuit. The way to test 
this is merely to substitute pressure for voltage and flow for current. 
Matter of fact, hydraulic systems use the same formulas as in ohms law, 
just the terms are re-named.

Most transformers used in amateur amplifiers are wound for ICAS 
(Intermittent Commercial and Amateur Service) where the transformer is 
about 1/2 the size as one used in CCS (Continuous Commercial Service). 
Even though surge current can hurt a CCS transformer too, it is worse on 
one that is ICAS if it is tied into the same type load. About the only 
difference you'll see between the two PSU's in most is the transformer. 
The PSU's will most likely have the same rectifiers and capacitors or 
close to the same circuitry and the load resistance. That is about all 
I've ever noticed between the two in amateur service. This being one 
saying CCS and the other ICAS. To me, I would rather bring one up slower 
and save the PSU's life expectancy. This is just my opinion of course.

Best & 73's

Will Matney


Hanson, Dick wrote:

>Hi Will....
>
>Not to be critical of all the nay-saying with regard to the
>above.....'cause I'm not smart enough to argue the point
>technically......but here are my limited observations from a
>dxexpeditioning and contesting point of view.
>
>1) All the arguments that use words like "would, might, perhaps, not too
>healthy etc" are, theories. Heck, some parts of these theories may even
>hold water.
>2) I have owned one sort of Command amplifier or another now for over 12
>years and have never experienced a failure of anything in the power
>supply chain......equalizing resistors, Nichicon electrolytics, diodes
>or power trans. Oh and yes, the Crydom zero-crossing relays have hung in
>as well. I am not endorsing his products, but thus far, at least I've
>been fortunate not to have had failures.
>3) Because of number 2 (above), I have constructed seven or eight rather
>hefty power supplies for home and contesting use. They all use the pair
>of relay approach to being switched on. So far, no failures.
>
>FWIW
>73
>Dick, K5AND
>
>
>
>
>__________ NOD32 1.880 (20040928) Information __________
>
>This message was checked by NOD32 antivirus system.
>http://www.nod32.com
>
>
>
>  
>