How exactly does a UPS work?

Thread Starter

Antonyc

Joined May 17, 2016
16
SCR, that is very interesting, but what worries me is that there is no locking mechanism, and relays are consumable items. So, if mains live was connected to the load, but solar neutral was welded shut, I'd have mains live running through my building, going through my inverter's neutral! I have no idea what the effects of that are, but it's certainly not ideal. Infact, wouldn't that trip my house RCD?
 

falade47

Joined Jan 24, 2017
178
I
SCR, that is very interesting, but what worries me is that there is no locking mechanism, and relays are consumable items. So, if mains live was connected to the load, but solar neutral was welded shut, I'd have mains live running through my building, going through my inverter's neutral! I have no idea what the effects of that are, but it's certainly not ideal. Infact, wouldn't that trip my house RCD?
Its not conventional..mains live should go through your form of switch, you could possibly have a common neutral point where both sources are connected directly together with the load
 

Reloadron

Joined Jan 15, 2015
7,501
DPDT, I'm switching mains L/N OR both solar L/N TO load L/N. Load is 250v 50Hz, single phase.
Why are you switching Neutral? Are you in the US? I ask as the Neutral is not generally switched. Do you have a link to the contactor you are using?

Here is an example of a typical AC transfer switch. Note in the specifications they call out "Maximum operating time of the relay 25 msec" and that is a maximum. When choosing an AC transfer switch system that maximum time is a prime consideration.

Using a home PC as an example if we look at the PC PSU specifications they call out a Hold Up Time:
3.2.11. Voltage Hold-up Time The power supply should maintain output regulation per Section 3.2.1 despite a loss of input power at the low-end nominal range—115 VAC / 47 Hz or 230 VAC / 47 Hz—at maximum continuous output load as applicable for a minimum of 17 ms.

I have a minimum hold up time and on the switch I have a maximum switch time and I work with numbers like this to design a suitable switch over system. You designed and built the system so all you can do is look at your options at this point.

Ron
 

Thread Starter

Antonyc

Joined May 17, 2016
16
Mr Reloadron,

I'm afraid that isn't true in the case of the switch which you posted. It says there in your link; "Uses heavy duty Double Pole Double Throw (DPDT) relay for switching both the Line and Neutral". As far as I know, that is standard practice, but what do I know? I live in the UK.

The contactor which I'm using (isn't, but) looks similar to this one:
http://www.tme.eu/gb/details/lc1d09...A73YxA5JRF3V3SOkoVRm0W0BAX7z6mPhoC16QQAvD_BwE

I'll investigate joining the neutrals...

Thanks, Antony
 
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