265. Minimum thicknesses of enclosure Polymeric Material
Polymeric Material The encapsulation Epoxy as watertight Enclosure A one-piece, molded coil form in contact with water
Minimum Thickness 1/8 inch (3.2 mm) 1/32 inch (0.8 mm)
Minimum thicknesses of enclosure metal
At curved, ribbed, or otherwise reinforced
surfaces and at surfaces of a shape or size, At surfaces to which a At surfaces intended
At unreinforced, flat or both, to provide the necessary mechanical wiring system is to be for
Metal surfaces in general strength connected in the field outdoor use
Cast Metal Nonferrous Die-cast metal
such as Aluminum-
, Magnesium-, 5/64 inch (2.0 mm) 3/64 inch (1.2 mm) - -
Zinc- or Copper-
based alloy
Ferrous Cast malleable
3/32 inch (2.4 mm) 1/16 (1.6 mm) - -
iron
Ferrous or Other cast metal
1/8 inch (3.2 mm) 3/32 inch (2.4 mm) - -
Nonferrous
Sheet Ferrous Uncoated sheet
0.026 inch (0.6 mm) 0.032 inch (0.81 mm) 0.032 inch (0.81 mm)
Metal steel
Galvanized
0.029 inch (0.74 mm) 0.034 inch (0.86 mm) 0.034 inch (0.86 mm)
sheet steel
Nonferrous Sheet aluminum
0.036 inch (0.91 mm) 0.044 inch (1.2 mm) -
Sheet copper or
0.033 inch (0.84 mm) 0.043 inch (1.09 mm) -
sheet brass
- Surfaces in relatively small areas or surfaces that are curved, ribbed, or otherwise reinforced may be less than the specifications in the first column of thicknesses.
266.
267.
268. A – Region to be shielded by barrier. This will consist of the entire component if it is not otherwise shielded, and will
consist of the unshielded portion of a component which is partially shielded by the component enclosure or equivalent.
B – Projection of outline of component on horizontal plane.
C – Inclined line which traces out minimum area of barrier. When moving, the line is always:
1) Tangent to the component,
2) 5 degrees from the vertical, and
3) Oriented so that the area traced out on a horizontal plane is maximum.
D – Location (horizontal) and minimum area for barrier. The area is that included inside the line of intersection traced
out by the inclined line C and the horizontal plane of the barrier.
269.
270.
271.
272.
273.
274.
275.
276.
277.
278.
279.
280.
281.
282.
283.
284.
285.
286.
287.
288.
289.
290. Galvanization (or galvanisation)
classically refers to any of several electrochemical processes named after
the Italian scientist Luigi Galvani.
Now the term generally refers to an electrodeposition process used to
add a thin layer of another metal to an item made of steel, in order to
prevent rusting.
More recently, though, the term has been broadened in common usage
to include applying a protective metallic coating to an underlying piece
of metal, using a process called hot-dip galvanization, which produces
similar results, but which does not employ electrochemical deposition.
291.
292.
293.
294. A zinc coating, other than that provided on hot-dipped, mill-
galvanized sheet steel(ASTM A653/A653M)
295.
296. Phosphate conversion coating are used on steel parts
for corrosion resistance, lubricity, or as a foundation for
subsequent coatings or painting. It serves as a conversion
coating in which a dilute solution of phosphoric acid and
phosphate salts is applied via spraying or immersion and
chemically reacts with the surface of the part being coated to
form a layer of insoluble, crystalline phosphates.
Phosphate coatings are often used to provide corrosion
resistance, however, phosphate coatings on their own do not
provide this because the coating is porous. Therefore, oil or
other sealers are used to achieve corrosion resistance.
297. Black Oxide (historical uses of black oxide, Bluing) is a
conversion coating formed by a chemical reaction produced when
parts are immersed in the alkaline aqueous salt solution operated at
approximately 285 °F (141 °C). The reaction between the iron of the
ferrous alloy and the hot oxide bath produces a magnitite (Fe3O4) on
the actual surface of the part. It is possible to oxidize non-ferrous
metals under suitable conditions to form black oxides.
Black oxide provides minimal protection against corrosion, unless
also treated with a water-displacing oil to reduce wetting and
galvanic action.
The oldest and most widely used specification for hot black oxide is
MIL-DTL-13924, which covers four classes of processes for different
substrates. Alternate specifications include AMS 2485, ASTM D769,
and ISO 11408.
298. Conversion coatings are coatings for metals where the part surface is
converted into the coating with a chemical or electro-chemical process.
Examples include chromate conversion coatings, phosphate conversion
coatings, bluing, black oxide coatings on steel, and anodizing. They are used
for corrosion protection, increased surface hardness, to add decorative color
and as paint primers. Conversion coatings may be very thin, on the order of
0.00001". Thick coatings, up to 0.002", are usually built up on aluminium
alloys, either by anodizing or chromate conversion.
Passivation is the process of making a material "passive", usually by the
deposition of a layer of oxide on its surface. In air, passivation affects the
properties of almost all metals–notable examples being aluminium, zinc,
titanium, and silicon. In the context of corrosion, passivation is the
spontaneous formation of a hard non-reactive surface film that inhibits further
corrosion. This layer is usually an oxide or nitride that is a few nanometers
thick.
299.
300. Cadmium plating
Cadmium plating (Electroplating) is under scrutiny because of the
environmental toxicity of the cadmium metal. However, cadmium
plating is still widely used in some applications such as aerospace
fasteners and it remains in military and aviation specs. Cadmium
plating (or "cad plating") offers a long list of technical advantages
such as excellent corrosion resistance even at relatively low
thickness and in salt atmospheres, softness and malleability,
freedom from sticky and/or bulky corrosion products, galvanic
compatibility with aluminum, freedom from stick-slip thus allowing
reliable torquing of plated threads, can be dyed to many colors and
clear, has good lubricity and solderability, and works well either as
a final finish or as a paint base.
301.
302.
303.
304.
305.
306.
307. Sand-cast
The most widely used
casting process,
utilizes expendable
sand molds to form
complex metal parts
that can be made of
nearly any alloy.
332. IEC 60364 LOW-VOLTAGE ELECTRICAL INSTALLATIONS
TN-C
TN TN-S
T TN-C-S
IEC classifications of TT
Power Distribution
network Systems
I IT
Based on the Earthing of transformer secondaries
334. Typical U.S. Power Distribution network
Three-phase Single phase Three-phase
transformer secondary transformer secondary transformer secondary
(U.S. commercial 120/240 V) (U.S. residential 240/120 V) (U.S. commercial 208/120 V
and 480/277 V)
(Europe et al 230/400 V)
348. Table 400.4 Flexible Cords and Cables
S Hard Service (600 V)
SJ Hard Service, Junior (300 V)
E Thermoplastic Elastomer (After first letter)
T Thermoplastic (After first letter)
- No T or E means Thermoset by default.
O Oil-resistant. Single “O” means outer jacket only is oil resistant; double “O”
means both outer jacket and inner conductor insulation are oil resistant
W Weather-resistant. (Both Water and Sunlight resistant, suitable for outdoor use)
H Heater
V Vacuum Cleaner
E Elevator (As first letter)
EV Electric Vehicle
T Tinsel (As first letter)
P Parallel
NI Non – integral
-1 Insulation thickness for Parallel cords, thinnest to thickest. Actual insulation
–2 thickness varies with cord type and AWG size
-3
349. Branch Circuit. The circuit conductors
between the final overcurrent device
protecting the circuit and the outlet(s).
350.
351.
352.
353.
354.
355.
356.
357. NEC RECEPTACLE RULES SHAPE THE POWER SUPPLY
CORD LENGTH OF APPLIANCE IN UL STANDARDS.
358.
359.
360.
361.
362.
363. If > 50 % , marking Connect Only To A
Dedicated Branch Circuit.applicable.
379. The intent is to ensure
enough slack for the
terminal connections to be
made easily.
380. ARTICLE 314— OUTLET, DEVICE, PULL,
AND JUNCTION BOXES; CONDUIT
BODIES;FITTINGS; AND HANDBOLES
314.16 Number of Conductors in
Outlet, Device, and
Junction Boxes, and Conduit Bodies.
(B) Box Fill Calculations.
UL 778
381. ARTICLE 430— MOTORS, MOTOR CIRCUITS,
AND CONTROLLERS
430.12 Motor Terminal Housings.
Table 430.12(B)
UL 778
382. ARTICLE 430— MOTORS, MOTOR CIRCUITS,
AND CONTROLLERS
430.12 Motor Terminal Housings.
Table 430.12(C)(1) and Table
430.12(C)(2)
UL 778
390. Electrical Rigid Metal Conduit (RMC) Intermediate Metal Conduit (IMC) Electrical Metallic Tubing (EMT)
RMC is the heaviest-weight and thickest-wall steel conduit.
IMC has a thinner wall than RMC and weighs about one-third less than RMC.
EMT is the lightest-weight and thinnest-wall unthreaded steel conduit and also
commonly called thin-wall conduit.
