question

janvi avatar image
janvi asked

Why do we switch the AC Neutral ?

The contactors or relays inside Multiplus (and probably Quattro and others) show a circuit diagram for switching off the neutral conductor to AC mains. I wonder about the reason for doing this as is not used in all the remaining AC installations. Exeptions are for appliance behind „Schuko“ type connectors where hot conductor and neutral can be exxchanged depending from the plug direction. If the neutral switching to public AC grid is for regulation purpos only, what could be the reason for this rule ? For my experience, the neutral switching is a big danger for asymmetric loads in 3 phase grids. Anyway transfer switches have high efforts to reconnect the disconnected neutral to earth again using late break / early make contactors.

At least with the use of own grid transformer who produces non public neutral, I cannot see any reason on why not to connect all neutrals permanently. If there is any remaining neutral current, it will not be registered in any kilowatthours registration devices. If this is possible (or recommended) there would be the possibility to improve the resistance of the used contactor with parallel use of the 3 or 4 available NO switches.

ac coupling
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3 Answers
Alexandra avatar image
Alexandra answered ·

@Janvi

The simple reason is for total isolation.

If there is a fault the neutral can be live. And a fire can still be sustained this way.

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kevgermany avatar image
kevgermany answered ·
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janvi avatar image janvi commented ·

the shown thread discuss about why to connect Neutral with Earth what is no question for non vehicle installations. The question is why transfer switches interrupt this connection and then replace with the same earth at other location


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janvi avatar image
janvi answered ·

Many thx to Alexandra for this simple answer. If there is a fault in electricity, there is always any risc of fire. The switch simply moves the area of responsiblity for possible faults what encourages me to deviate from that rule with my own transfer switches


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