Date: Wed, 24 Feb 2010 09:21:39 -0300
From: Felipe Ceglia - PY1NB <felipeceglia2@gmail.com>
Subject: Re: [Amps] soft start, how to determine if needed?
To: Edward Swynar <gswynar@durham.net>
Cc: Amps@contesting.com
Message-ID: <4B8519D3.90203@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Folks,
Thank you for your replies.
Is there a way to calculate what R values and relay contact Amp rate
should I need?
Also, if the primary is feed with 110+110 volts, I should use one R on
each primary leg winding, right?
73 tu,
Felipe - PY1NB
## IF the total Voltage is 220 vac across the entire pri winding,
[even if it's TWO x 110 vac winding's in SERIES], you only require
ONE step start resistor... inserted into ONE leg. [either leg]
## Typ R value is 10-25 ohms. 25 ohms is a good value for most small
amplifiers, and 25-50 uf of filter C. Typ wattage is 50-100w.
Use either a wire wound resistor on stand-off's.. OR an Arcol type resistor
[ metal finned type, no standoff required, bolted directly to chassis, or side
wall]
### 220 v / 25 ohms = 8.8A when power applied. I'd suggest using a
20-40A rated relay to short out the 25 ohm resistor. [SPST] This SPST
relay will have to handle the FULL current, once energized.
## I'd also suggest a 20-40A rated DPST to apply the 220 vac.
## Wiring from 25 ohm resistor to SPST step start relay does NOT have to
be big ga. It will only have to handle 8.8A for 1-5 seconds. 12-16 ga is
plenty
big enough. Just make sure all connections are solid. ALL other 220 vac
wiring
should be sized for minimal V drops
Later... Jim VE7RF
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