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IntraWinding

Fri Jul 23 2010, 04:45PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

coillah wrote ...

Here's a pic of my chamber I am building.

1279841224 1517 FT92744 My Senior Project Is Better Than Yours

Nice! What will you use it for?

doctor electrons

Fri Jul 23 2010, 09:12PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

I agree, that thing is pretty!! You should be ok with the zero awg at 150 amps as long as there won't
be any large inrush or surge currents that pass the cables rating.

radiotech

Sun Jul 25 2010, 06:56AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Ampacity is a system of rating wire and cable insulation and their raceways on temperature of the environment they are in. It also has the effect through regulation of sizing hardware and overcurrent protection settings.

Regulations aside the sizing of the conductor just depends on what resistance you can tollerate. You may even desire the conductor to fuse under severe overload.

doctor electrons

Sun Jul 25 2010, 01:31PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

radiotech wrote ...

Ampacity is a system of rating wire and cable insulation and their raceways on temperature of the environment they are in. It also has the effect through regulation of sizing hardware and overcurrent protection settings.

Regulations aside the sizing of the conductor just depends on what resistance you can tollerate. You may even desire the conductor to fuse under severe overload.

Yes. Yes. Agreed.
On this note! Overcurrent protection devices can also govern wire sizes. For example, say you have a large distribution block that carries
0 awg wire on its line side. The load side will not have any 0 awg connections and will usually be rated for a wire that is 14 awg minimum.
14 awg is only good for 15 amps, according to ul and nec. The reason this can be done "safely" is the condition that there is a specific
fuse type in front of that distribution block, usually class j, and over current devices like breakers after the block and before the loads.
This type of setup is what you will see in almost every industrial electrical panel. Sometimes the rules dont make any sense but after
carefully considering their reasoning they get a bit less foggy. There is also another wire sizing table in the nfpa70, have a look at that
one! It is completely different from the nec and ul tables!

radiotech

Sun Jul 25 2010, 03:50PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The general rule is when ever a conductor is fed from a larger size conductor protection applies. Then there are the tap rules which forego protection based on length of tap. Example 30 amp wiring may feed a 30 amp disconnect close to a 1000 amp bus gutter. The reason is the top of disconnect may literaly explode if it fails but the enclosure will contain it. The tap circuit will clear leaving the bus operating. This is the reason electricians operated those disconnects in such a way so the door, if it blew open wouldn't smack them in the face. Nowadays arc flash protective suits must be located in switchrooms.
An interesting rule concerns firepumps. You can reduce protection on these circuits because you aren't worried about the pump motor catching fire if the building is on fire and the pump is delivering water to the sprinklers or hose stands
Most codes have "code handbooks" which are different from the code rule book, in that they state the reason for the rule.. History shows Edison simply stole the distribution plan for his system by finding out exactly how the system of gas pipes reduced their diameters along the way while fanning out to the houses from the mains.
Edison was angry at the arrogance of the lighting gas companies which drove him to perfect a system to overthrow their monopoly. Perhaps a new Edison will overthrow the oil cartel by making something that works for cars.

doctor electrons

Mon Jul 26 2010, 02:27AM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

That is the coolest danger sign i have ever seen!! That looks like an old book, i am a huge fan of old books!
I sure hope someone knocks the oil companies out of the drivers seat!! That would be a refreshing change.
I think these guys should worry less about how many billions of dollars they can pocket and more about
keeping the earth clean, while keeping money in our pockets. Thats a whole different thread!
Back to the convo, arc flash rules are increasing! I notice more and more at work. The latest and greatest is
putting on the space suit whenever we do testing on a live panel, along with the usual safety barrier in place around
the area. Friday i was told we now need to place arc flash warning labels (the ones with the ppe statements) on every
enclosure that it is fed with 50vac, 50vdc, or higher. I recently heard a rumor about state regulation getting larger.
Supposedly a license will be required to build any electrical equipment. This would be aside from the journeymans card
i already hold. In other words, non-state licensed individuals would not be allowed to work on any electrical equipment.
I suppose that is fine, just another 100 bucks to take a test and another 100 to renew every year.

klugesmith

Mon Jul 26 2010, 05:47AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I didn't realize arc flash suits & warning signs are so prolific nowadays.
There's a lady I work with whose (now ex-) husband suffered life
altering burns in an arc flash accident 10 years ago.

doctor electrons

Mon Jul 26 2010, 09:38PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

Thank god he survived! Not only are many electricians killed by arc flash, they suffer miserably
before they pass on. I would assume this gentleman suffered the same way, and most likely still is.
I understand the need for protection and a lot of my fellow electricians complain. Some make comments like
"This damn suit makes my job more dangerous because i cant see a thing, these stupid gloves are like oven
mitts!!!" It does not bother me, i want to keep all of my fingers and both of my eyes. Oh yea, my face to!

radiotech

Mon Jul 26 2010, 10:56PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

.
The issue today is the advanced engineering of electrical gear, which makes it smaller, better and more dependant on proper application and operating procedures. Gone are the heavy contactors with mineral based insulation that could survive a minor sunburst and be repaired with just a few parts.

You add that to the difficulty in finding trained and long experienced electricians, the workplace safety people dont want to pay out the rehab/medical costs.

coillah

Mon Jul 26 2010, 11:59PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

doctor electrons wrote ...

I agree, that thing is pretty!! You should be ok with the zero awg at 150 amps as long as there won't
be any large inrush or surge currents that pass the cables rating.

The load side will be purely resistive. On the high voltage side of the xfrmr I'll have a nice SCR power controller with soft start. It's amazing how much cheaper you can make these systems when you don't rely entirely on a distributor like KJL. All the components they sell are obscenely marked up (power controllers, wiring harnesses, transformers, even the evaporation plate)! Plus, I'll get more features from the equipment I found/ make on my own.

Still have an amazing amount of work left to do on this project though... Hopefully I can finish it before I graduate :D

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