Re: My electricity experiments aka How I failed again
Posted: Tue Sep 16, 2008 5:43 am
No, you don't.inflater wrote:At least I know how it tastes to be a high voltage electrician.
When an inductor is connected to electricity it builds up a magnetic charge. If the electricity is disconnected while this magnetic charge is still present it retains this charge (and old TV coils can hold a magnetic charge for up to about 10 days - newer TV coils have built-in resistors to prevent them from holding the magnetic charge). When something (e.g. a moron) makes contact with the inductor the magnetic field collapses, resulting in a DC voltage - in your case, a relatively high DC voltage that drops extremely quickly to zero, which would feel similar to a large electro-static discharge.
I am a "low voltage" electrician (a licensed electrical contractor to be exact, which is similar to "electrician" except I can legally run my own business, bid for contracts, employ electricians and subcontractors, etc - a normal electrician is only licensed to do electrical work and can't do any of the other things). Around here it's 240 volt AC (single phase) and 415 volt AC (three phase). There's 2 major differences here. First, it's AC, which makes your muscles contract and relax in sync with the supply frequency (50 times per second around here). This means that if you grab live wires with your hand (for e.g.) you have no control over your grip and can't let go. It also places serious stress on your muscles, and can confuse the timer that keeps your heart beating (something called "fibrillation" can occur, where your heart fails to beat normally after the electricity is disconnected and you die within a five minutes after being disconnected from the electricity). The stress on the muscles is another problem - it weakens the muscle, and it can cause heart failure up to 24 hours later (even though you feel fine after the shock), which is why the OH&S (Occupational Health and Safety) laws here require you to spend 24 hours in hospital under observation after you've had an electric shock. The other difference is that there's nothing to limit the current - under short circuit conditions you get between 5000 and 45000 amps (usually extremely briefly, due to the use of circuit breakers and fuses at each level in the supply), but these circuit breakers and fuses won't interrupt the supply until there's enough current passing through them, and a human has sufficiently high resistance that there's never enough current passing through the circuit breakers/fuses (unlike your "collapsing magnetic field", which would run out of charge after about 10 ms).
Of course the low voltage supply comes from the secondary side of step-down transformers you see in the street.
"High voltage" is defined as 1000 volts AC or 1500 volts DC (or higher). Around here a "high voltage electrician" works with the voltages on the primary side of the step-down transformers you see on the street. This is 3500 volts or higher (going up to about 150000 volts). This is AC volts *without* current limiting (except for short-circuit protection, but with tens of thousands of volts and hundreds of thousands of amps you'll be a crispy corpse before the short-circuit protection has enough time to do anything - I'll let you work out how many watts). Also, at these voltages you don't need to touch the wires to get cremated - depending on voltage it can jump over a 70 mm air gap. That's why "high voltage electricians" have 2 meter long fiberglass handles on all their tools, and also why they make sure those handles are *spotlessly* clean.
The other thing I wanted to mention (in case you were thinking of doing something in this field as a career), is that you've probably blown your chances of getting a job (assuming you live that long). I employed several people ("trade assistants" mostly) when I was running my electrical contracting business, and I've interviewed potential employees enough times to know how it works. As soon as the potential employee says they did anything electrical themselves (e.g. installing their own power outlets) the interview stops and the interviewer (me) asks a few questions about the weather to be polite before saying those immortal words - "we'll let you know...". Basically anyone who lacks adequate respect for electricity (like you) is too much of a risk for anyone to employ or train. Think of it like this, if you were running a fireworks company and if you were responsible for the safety of your employees and the safety of your customers, would you employ someone that likes to play with matches?
Cheers,
Brendan
Of course you are way more experienced in both subjects than I am, I agree.
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