DEFINITIONS OF TECHNICAL TERMS (IN NON-TECHNICAL LANGUAGE)
Electrical Terms
Corona - More properly known as Partial Discharge - Low-level passage of
high-voltage current through a gas, usually air, due to ionization of the
air or gas. In the case of air, corona creates highly-active ozone, which
can cause severe chemical damage to organic compounds and materials
nearby. May be audible (a hiss) and visible (a blue glow).
Corona Resistance - Or Voltage Endurance (similar terms) - Ability of
the insulating material to withstand damage caused by voltage stress.
Dielectric Strength -- Voltage required to puncture the material. May be
Direct Current or Alternating Current (DC or AC), at many test conditions.
Often measured by ASTM Standard D-149.
Dielectric Constant - Measures the capacity of the material to store
energy relative to a vacuum. Generally, the lower the better for insulation
use since it also measures how much AC leakage current can flow through
the material. Often measured by ASIM D-150.
Dissipation Factor - Relates to energy which can be lost in the
insulating material due to AC current flow (capacitive current). Usually
measured by ASTM D-150.
Impulse Dielectric Strength - Ability to resist a very short pulse
of high voltage, such as a lightning strike, with a duration usually on the
order of 1 / 1,000,000 second rise time. Measured by ASTM D-3426.
Resistivity - Or Conductivity (two sides of the same coin) --
Measures the current-carrying ability of an insulating material -as if
treating the insulating material as a conductor. Measured by ASTM Test D-257.
Other Terms
Breaking Elongation - Amount the material will stretch under tensile
stress before breaking. Measured by ASTM D-828.
Calender -- Pass paper between rollers at high-temperature and
high pressures to increase density, properties, and surface smoothness.
Usually used with high-quality papers. NOMEX ® papers, except for
Types 411 and 419, have been calendered.
Initial Tear Resistance - Ability of the material to resist tearing when
a force is applied which tends to tear an edge of the material. Usually tested
by ASTM D-1004.
Power Frequency - frequency of the sine-wave power in Hertz
(formerly referred to as cycles per second). Usually 60 Hz in the U.S.,
50 Hz in Europe and parts of Asia, etc.
Harmonics - Multiples of the power frequency of a power line,
such as 120 Hz, 180 Hz, 600 Hz., etc. The higher the harmonic content,
the higher the risk of damage to the equipment due to corona (partial discharge).
Tear Propagation Strength - Measures the ease with which a tear
which already exists can be further extended. Usually measured by
TAPPI Test T-414, Elmendorf Test.
Tensile Strength - The ability of the insulating material to resist
straight line forces without breaking. Usually measured by ASTM D-828.
Thermal Conductivity - Measures the speed with which heat is
transmitted through the material. The higher the thermal conductivity of
the insulation, the easier it is to cool the electrical equipment by transferring
heat to the metal parts of the machine, or to the air.
Temperature Conversions Dimension Conversions
C F in mm mils
100 212 .002 .051 2
110 230 .003 .076 3
120 248 .004 .102 4
130 266 .005 .127 5
140 284 .006 .152 6
150 302 .007 .178 7
160 320 .008 .203 8
170 338 .009 .229 9
180 356 .010 .254 10
190 374 .015 .381 15
200 392 .020 .51 20
210 410 .025 .635 25
220 428 .030 .762 30
230 446 .050 1.27 50
240 464 .100 2.54 100
250 482 .200 5.08 200
260 500 .300 7.62 300
.400 10.2 400
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® is P. Leo & Co., Ltd. trade mark.
Nomex® Mylar® and Kapton ® are Du Pont registered trade marks.
© P. LEO 1996
