What causes an electrical short circuit?
An enormous variety of situations can cause a short circuit.For example, insulation between two wires breaks down (due to age, environment, abrasion) or is damaged (cut or scraped away). Zap.A component breaks down, so that its resistivity goes to zero and its conductivity becomes very high. Zap.A metal tool or other conductive item is dropped or laid across two terminals. Zap.Equipment is immersed in salt water. Zap.A suspended wire breaks, and drops onto another wire or a grounded metal object. Zap.An unwary person grasps a high-potential conductor or terminal, and touches ground or low potential with some other part of the body. Zap.An insulating barrier fractures or is removed. Zap.An idiot trying to do his own house wiring or appliance re-wiring touches two wires together. Zap.Get the idea?
What happens if 3 phase is short circuited?
You will blow fuses or trip a breaker upstream of the fault, well you SHOULD. Bolted three phase faults as you describe, are like driving a forklift through a conduit, which I wouldn’t necessarily use the word “rare” when describing their frequency of occurrence.The good thing about bolted faults, is that no matter the system design, you will trip short circuit current devices like fuses or circuit breakers, every time. We are on a high resistance grounding system, where bolted faults will trip the breakers, but ground faults will not. You have to chase down locations of ground faults, which can be time consuming.
Welding mig hardwire downhill then fluxcore vert. why?
For mild steel pipe, MIG short-circuit is obviously much faster than TIG or stick for the root pass. https://www.youtube.com/watch?v=8h5m7oHM... Short-circuit vertical down is a good technique for filling open root gaps. You only have a small amount of metal between the the two bevels to remove heat from the puddle, and cause it to freeze. So it's important to minimize heat input in the root. I wouldn't use flux core or dual shield for the root pass, way too much heat input. You'd be worried about slag islands in the root, and internal undercutting. "All position" flux core wires have a heavy, sluggish, fast freezing flux. Which creates excellent results for vertical up, since the slag naturally runs downhill away from the puddle. But it causes serious problems with slag inclusions and L.O.F. if you try and run it vertical down. Solid wire of course doesn't have flux so you can run it vertical down with less problems. If the pipe is under and kind of pressure, the inside surface of the pipe is where the maximum stress is going to be, especially between the 5-o-clock and 7-o-clock area. That's why the root is so critical.
How to ground something on a circuit board?
Okay so I'm new in circuitry I know that for DC the positive connects back to the negative but AC has "a 3rd wire" positive negative and the ground right? So how would you create a ground on a circuit board? Also on most circuit schematics I see I do not see the positives going back to the negative I only see the ground. So basically my questions are: 1 - How would you ground a wire for a circuit board say PCB board? 2 - Why do I not see the negative on a circuit schematic is this because it is already understood to connect negative back to positive? 3 - Where would the "3rd wire" come from on that of a 9volt battery?