If you switch at zero voltage, there is no EMF to drive a current through the
load impedance. A quarter cycle later, when there is EMF across the load, the
current will lead or lag by a factor depending on the phase angle and magnitude
of the impedance. So there's a difference between the transient condition
existing for the first part of the cycle - probably somewhere between 5 and 10
degrees - and the stabilised condition. But the initial switch of zero volts
must be with zero current.
73
Peter G3RZP
========================================
Message Received: Feb 10 2014, 06:24 PM
From: donroden@hiwaay.net
To: amps@contesting.com
Cc:
Subject: Re: [Amps] Solid State Relays Again
Quoting Peter Voelpel <dj7ww@t-online.de>:
> I guess with transformers the relay should switch in on the peak voltage.
> As current peaks 90 degree behind that should be the best moment with least
> surge current.
>
> 73
> Peter
But if you switch at zero voltage, the current is at zero 90 degrees later...
So you have at least 1/4 of a cycle where there is minimum IxE
supplied to the load.
Don W4DNR
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