Meter fuses?

[nagyrobi]

Hi Miro,

Quick question: what fuses do you recommend (if you recommend any at all) in front of the voltage meter transformers?

This is in your photo but can't really recognise if it's just a splitter or also includes a fuse:

[dzurikmiroslav]

Hi Robert,
Yes it's contain fuses, I don't remember exactly value, but very small value, like fast 0.2 0.5A.
Fuse terminal blocks are https://www.phoenixcontact.com/en-pc/products/fuse-modular-terminal-block-ut-4-hesi-5x20-3046032

[nagyrobi]

T or fast?

[dzurikmiroslav]

Just checked, I have installed T250mA fuses.

[nagyrobi]

Meanwhile I also looked at the metering transformers specs, it says it can max 2mA on both primary and secondary, so I guess anything above 10x that is overkill.

[dzurikmiroslav]

Yep, It's not protect transformers. But my friend who does electrical installations advised me that each conductor must have a fuse/circuit breaker rated for the maximum current of the conductor.

[nagyrobi]

Hm. That's true for energy distribution with variable loads, where you only protect the cables.

A 250mA fuse at 240V would let through 60 Watts. If there would be a short in the transformer leading to increasing currents the whole thing could still melt down at such power.

Not sure if the ZMPT has any inrush current (not stated in the sheet I've seen), it's rated to 2mA, has a linear range between 0-10mA (whatever that means). If we take 10mA, that's 2.4W.

If i would use 30mA fuse, that would protect at 7.2W. Still not small but probably not allowing to melt down.

Wild guesses from me, let alone I use the charger with no fuses at all on the meter lines since the summer but I'd like to change that.