Running 15 or 20A mill on 50A circuit breaker

Thanks everyone, I'm learning. I understand the most basic things about electricity and electronics, but breakers and wire gauges seem to escape me, lol.

I guess I think of breakers as being much the same as fuses. Thinking about it, fuses are there to protect the wiring, to prevent melt downs (and potential fires). So, if the milling machine I'm planning to buy specifies 240V and 9A full load current, as long as I don't have a <9A circuit breaker, just buy the correct plug for the 50A outlet on the wall, connect it to the wire from the machine, and start playing.

That's an easy solution. :cool:

Correct as above, this is another thing I like about this place. You can discuss electricity (which most of our machines need to function) and people with experience will respond. Any possible bad advice will be pointed out almost immediately thus keeping you safe unless you do something silly. Electricity is dangerous, but like anything dangerous it's better to have knowledge than be in the dark.... ;)

John
 
Correct as above, this is another thing I like about this place. You can discuss electricity (which most of our machines need to function) and people with experience will respond. Any possible bad advice will be pointed out almost immediately thus keeping you safe unless you do something silly. Electricity is dangerous, but like anything dangerous it's better to have knowledge than be in the dark.... ;)

John

Yep, I hang out here because I've learned a lot from people who have gone down these roads before me, and are willing to share their knowledge. There are other areas (e.g. motorcycles) where the roles are reversed, but here I'm the beginner, and that's fine. I like to research everything before I take any action. Look before you leap. With electronics and electrical stuff, that seems to be an especially important rule to live by. :encourage:
 
it should have tripped the breaker in under 100 milliseconds
Dabbler- I left a couple of details out of my "back in the day" story so it didn't go on and on. The isolation transformer was a fairly small one and the breaker was a "long delay" one. The impedance of the transformer in combination with the long, small cord is what caused my concern. I was surprised how fast it happened though.

Short circuits are only part of the story as people have mentioned above. Overloads can also happen and could potentially draw current that is below the current the breaker is rated to trip at but higher than the cord that connects the breaker to the machine can handle without overheating. In those cases, having a breaker that is more closely sized to the load is a good thing. It will trip in more cases than not. Chances of this happening without a machine fuse popping before causing any real harm are probably low. For me though, the cost of doing it right is low enough so you can avoid the risk.

cheers everyone!
 
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