[Amps] Solid State Relays Again
g8on at fsmail.net
Mon Feb 10 13:47:11 EST 2014
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.
Message Received: Feb 10 2014, 06:24 PM
From: donroden at hiwaay.net
To: amps at contesting.com
Subject: Re: [Amps] Solid State Relays Again
Quoting Peter Voelpel <dj7ww at 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.
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.
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