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220vac diode?

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jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Fri Aug 07, 2015 5:11 pm Post subject: 220vac diode?

I’m powering a device with two 220vac sources, one main and one backup. What kind of diode, or other one-way device can I use to prevent backfeeding a source wire when it should be off?

 

This project is taking place in Thailand that uses a neutral, 220 hot and a ground wire in household wiring.

 

Thanks,

John

  [quote][b]

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Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Fri Aug 07, 2015 5:58 pm Post subject: 220vac diode?

John;  

   

Not quite sure what type of “device” you may be referring to, but this sounds similar (or identical) to a backup generator situation for a house service. The device “normally” used to make the changeover from one source to the other is a transfer switch. Functionally it is basically a single pole double throw relay with the coil attached to the “main” or “primary” source. The primary source is also attached to the NO contact while the load is connected to the moveable or common contact, and the secondary source is connected to the NC contact.  

Functionally while the primary source is live the relay is “closed” and supplies the load form the primary source. Should the primary source be lost, the relay drops out and connects the load to the secondary or backup source through the NC contact.  With this method you do lose power for a few milliseconds during the transfer. Something to keep in mind if that would be critical to your use. When the primary source is restored the relay picks up and transfers the load back to the primary source. All automatically.  

   

Not sure if this is what you’re trying to achieve, but from your original request it sounds like it is.   

   

Diodes won’t do what you’re trying to accomplish because they are DC devices and won’t function in an AC circuit. If however your load is able to utilize DC power then you could rectify the AC through diodes (rectifiers) and then the paralleling of the sources through the diodes would work to prevent the back-feeding of one source into the other.  

   

Because you refer to household power I suspect that the relay/transfer switch method described above is what you’re after.  

   

Bob McC  

           

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of John Burnaby

 Sent: Friday, August 07, 2015 9:10 PM

 To: aeroelectric-list(at)matronics.com

 Subject: 220vac diode?  

  

   

I’m powering a device with two 220vac sources, one main and one backup. What kind of diode, or other one-way device can I use to prevent backfeeding a source wire when it should be off?  

   

This project is taking place in Thailand that uses a neutral, 220 hot and a ground wire in household wiring.  

   

Thanks,  

John   	  Quote: 	
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ronaldcox

Joined: 24 Jan 2008
Posts: 39

Posted: Fri Aug 07, 2015 5:59 pm Post subject: 220vac diode?

A diode won't work for AC, but something like a generator transfer switch would probably work.Â  

 It's just a powered relay. 

Ron Cox  On Aug 7, 2015 8:15 PM, "John Burnaby" <jonlaury(at)impulse.net (jonlaury(at)impulse.net)> wrote:[quote]

Iâ€™m powering a device with two 220vac sources, one main and one backup. What kind of diode, or other one-way device can I use to prevent backfeeding a source wire when it should be off?

Â 

This project is taking place in Thailand that uses a neutral, 220 hot and a ground wire in household wiring.

Â 

Thanks,

John

   	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


[b]

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Under Construction at C77 - Still just about to fly!

ceengland7(at)gmail.com
Guest

Posted: Fri Aug 07, 2015 6:23 pm Post subject: 220vac diode?

On 8/7/2015 8:10 PM, John Burnaby       wrote:

     

      	  Quote: 	
		                         <![endif]-->   <![endif]-->                

I’m powering a             device with two 220vac sources, one main and one backup.             What kind of diode, or other one-way device can I use to             prevent backfeeding a source wire when it should be off?         

          

This project is             taking place in Thailand that uses a neutral, 220 hot and a             ground wire in household wiring.         

          

Thanks,         

John       

       

     	
     If it's an AC device, diodes won't help.

     

     For a single ended AC source/load, a double throw switch or relay     would work to select source A or source B. 

     

     A SPDT relay with the A pole NO and the B pole NC, with the 220 VAC     coil powered by A, would switch and power the load from A until A     power is lost. It would then 'drop out' to the NC (B) pole, powering     the load from B.

     

     Charlie

      [quote][b]

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billp(at)wwpc.com
Guest

Posted: Fri Aug 07, 2015 6:54 pm Post subject: 220vac diode?

If it's two generators, the general procedure is to use synchronizing lights (or some type of phasing meter). What you need to do is start the first generator and close the output breaker (not closing it to the load but to the generators bus of the transfer switch). Then start the second generator and adjust the speed until the second generator is in phase and close its output  breaker. Both generators will stay in phase now on their own. You can parallel nearly as many generators as you like in this manor. Now you can flop the transfer switch to the generators. I did this every afternoon in Thailand during the rainy season in the mid '60's. 

If you are really talking about running a generator with the commercial mains, DON'T DO IT!

That's called back feeding the grid and you can kill someone who thinks the line is dead when in actuality you are feeding power to the commercial grid. This is illegal for good reason. There should always be a transfer switch between any generator power and the commercial mains that physically isolates two with no possibility of one being tied to the other.

Bill



Sent from my iPad



On Aug 7, 2015, at 18:58, Ronald Cox <flyboyron(at)gmail.com (flyboyron(at)gmail.com)> wrote:

[quote]

A diode won't work for AC, but something like a generator transfer switch would probably work.  

 It's just a powered relay. 

Ron Cox  On Aug 7, 2015 8:15 PM, "John Burnaby" <jonlaury(at)impulse.net (jonlaury(at)impulse.net)> wrote: 	  Quote: 	
		  

Iâ€™m powering a device with two 220vac sources, one main and one backup. What kind of diode, or other one-way device can I use to prevent backfeeding a source wire when it should be off?

 

This project is taking place in Thailand that uses a neutral, 220 hot and a ground wire in household wiring.

 

Thanks,

John

   	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	






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[b]

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ronaldcox

Joined: 24 Jan 2008
Posts: 39

Posted: Fri Aug 07, 2015 7:03 pm Post subject: 220vac diode?

I'm pretty sure he knows that he shouldn't back feed the mains, and is

trying to correctly prevent the situation your bringing up.



I believe he's trying to switch safely between, not parallel, two sources.



Ron Cox



On Friday, August 7, 2015, Bill Putney <billp(at)wwpc.com> wrote:



[quote] If it's two generators, the general procedure is to use synchronizing

 lights (or some type of phasing meter). What you need to do is start the

 first generator and close the output breaker (not closing it to the load

 but to the generators bus of the transfer switch). Then start the second

 generator and adjust the speed until the second generator is in phase and

 close its output  breaker. Both generators will stay in phase now on their

 own. You can parallel nearly as many generators as you like in this manor

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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_________________
Ron Cox
Glasair Super II F/T
Under Construction at C77 - Still just about to fly!

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Mon Aug 10, 2015 9:16 am Post subject: Re: 220vac diode?

Hey All, 

Thanks for your suggestions on how to isolate the mains from the back-up power so no one gets fried when BU pwr is on. The system works well and is safe in all configurations. Also thanks for cluing me in on diodes only being for DC.



Now back to aviating.



Cheers,

John



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