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Date: Tue, 23 Aug 2011 15:53:57 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: The Case for Solid state Relays (SSR)
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Kelly Troyer wrote:
> Ernest ,
>    Are you saying that when your SSR was activated it would not allow 
> battery voltage to your
> PM alternator regulator ??

Yes.  And a short investigation uncovered information that the 
regulators are designed so that they have to sense a voltage before 
they'll turn on.  Not an issue when controlling a motor, as Jarrett is 
considering, but a complete deal breaker when that supply line is also 
the monitoring line.

If used to control an alternator, the sense line would need some scheme 
to bypass the SSR.  The electrons only flow in one direction through the 
SSR, so the sense line will have to be on the battery side.

I'm not an EE.  Lots of other people know more about this than I.  
YMMV.  Void where prohibited. ETC.

I replaced the SSR with a 60A fusible link.  If the 38A generator blows 
that, it ain't coming back into service on that flight anyway.  I 
thought about replacing it with a contactor, but I already have a 
limited power budget.  A mechanical switch was a possibility, but the 
cabling and linkage start to become a headache.  At some point you have 
to admit that it is a VFR machine, and the extra complexity is going to 
cause more problems than it solves.