[RE-wrenches] AC Coupling Relays

[Exeltech]

Focus is on the relay contacts.  Any good designer will have already incorporated protective diodes for relay DC coils, so nothing needed unless specifically stated in the instruction/installation manual.

Do NOT connect any diodes across the relay contacts.

Bob Gudgel is 100% on target with his comments (below).


Dan

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On Mon, 6/16/14, Mac Lewis <maclewis1 at gmail.com> wrote:

 Subject: Re: [RE-wrenches] AC Coupling Relays
 To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
 Date: Monday, June 16, 2014, 10:59 AM
 
 Hi Drake,

I think you can put a power diode in parallel to the gt inverter that can conduct that inductive current if you need to.  However, I think BoB is correct, there should just be induction of the wiring itself for most grid-tied inverter.  The relay engineer recommended this diode for a DC load break application I recently had, so I assume AC would be the same.

Thanks

 
On Mon, Jun 16, 2014 at 9:11 AM, boB at midnitesolar.com <boB at midnitesolar.com> wrote:

   
Since grid-tie inverters sell back with a power factor of 1, the load ~should~ be entirely resistive and
not inductive or capacitive so a appropriately rated relay contacts ~should~ be fine.
 
Except maybe if the inverter is designed to supply VARs like the  last Solar-Pro magazine talks about.
(haven't actually read that article yet but I assume that's what it is about)
 
Of course, others may have different experiences so I would listen to them.
 
I prefer to use a somewhat over-rated relay.
 
boB
 
       
 
       
 
On 6/16/2014 7:05 AM, Drake wrote:
     
Hello Wrenches,
 
Do the relays that break the current from the direct grid tie
inverters, in AC coupled systems, need to be motor rated or can
they simply be rated for the amperage of the inverter output? How inductive
is the current between the two inverter systems? Will the current tend to jump
the contacts on a non motor rated relay, or burn them out prematurely?
 
Thanks,
 
       
 
Drake 
 
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV 
740-448-7328
http://athens-electric.com/