Safety in off grid transformerless inverter

[neonwarrior]

Hello everyone,

Is it safe to touch with your body, the low voltage (say 12V) pv panels non-insulated wires connected to an off-grid transformerless inverter?

The topology of the inverter is: First a Boost dc-dc converter ( maybe two stages) and then an h-bridge (output 220VAC).

My question is because of the high voltage at the output not from the solar panel voltage.

Thanks in advance,
Hyu

 

[Easy peasy]

haha - usually a grid tied transformerless inverter usually has at least 90V input from a PV string - touching any part of the PV string while the inverter is putting current into the mains should give you a shock ....

 

[mtwieg]

Definitely not. In order for your full bridge to put our 220V, the ~400V DC supply from the boost will need to have a common mode voltage with a large AC component (depending on how the PWM modulation is handled). Much like how it's not safe to touch either side of the DC output of a full bridge rectifier connected directly to the mains.

Using a bipolar DC output (+/-400V) would allow you to connect the battery ground to AC neutral, which would make it somewhat safer. But still not safe in a single fault condition (what if the neutral connection is broken while the hot connection remains?).