REPLACING AC BREAKER FOR DC BREAKER 1

[gpsolar]

Can I use an AC breaker in place of a DC breaker. What about the rating? Can I us the same current ratings?

 

[ScottyUK]

Possibly. A dumb thermal-mag breaker can sometimes be used for either but DC duty, if permitted at all, typically multiple poles in series to break the arc. Specifically which breaker are you talking about?


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If we learn from our mistakes I'm getting a great education!

 

[gpsolar]

A 100 A breaker for the DC input if an inverter. A two pole sigle throw or doublee throw

 

[jraef]

You must be confusing your terminologies. "Double throw" would never apply to a circuit breaker. Do you mean a relay or contactor perhaps?

 

[Skogsgurra]

Let's say it is a single-throw. And a breaker.

The problem with DC is, as we all know, that it never goes though zero - and therefore has no natural arc "extiguishing point" like AC has.

But that doesn't mean it cannot break DC. Only at lower voltage and current. Those data are usually specified along with different AC ratings. At least if we are talking contactors. For breakers, it is less common to see DC specs if the breaker isn't made for DC.

Breaking current for the DC link for an inverter could be quite easy, actually. Especially if the breaker is fed from a rectifier and feeds into a DC link capacitor. Then, the slightly pulsating, rectified mains voltage will create six zero crossings compared to the DC link voltage each period. So it should be easy to break.

But, beware! If it is a CSI inverter or if there is a heavy DC link inductor, you may be in deeper water than you want to be. Inductive loads and DC always need careful design. And the use of an AC breaker should not even be contemplated.

Gunnar Englund

http://www.gke.org

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