2
1.2 Glossary of Terms
Alternating Current, AC: Current that reverses direction on a regular basis, commonly in the U.S.A.
60 per second, in other countries 50 times per second.
Breakdown: The failure of insulation to effectively prevent the flow of current sometimes
evidenced by arcing. If voltage is gradually raised, breakdown will begin suddenly at a certain
voltage level. Current flow is not directly proportional to voltage. Once breakdown current has
flown, especially for a period of time, the next gradual application of voltage will often show
breakdown beginning at a lower voltage than initially.
Conductive: Having a volume resistivity of no more than 10
3
ohm-cm or a surface resistivity of no
more than 10
5
ohms per square.
Dielectric: An insulating material that is positioned between two conductive materials in such a
way that a charge or voltage may appear across the two conductive materials.
Direct Current, DC: Current that flows in one direction only. The source of direct current is said to
be polarized and has one terminal that is always at a higher potential than the other.
Hipot Tester: Common term for dielectric-withstand test equipment.
Insulation: Gas, liquid or solid material which has a volume resistivity of at least 10
12
ohm-cm and
is used for the purpose of resisting current flow between conductors.
Insulation Resistance Tester: An instrument or a function of an instrument capable of measuring
resistance's in excess of 200 megohms. Usually employs a higher voltage power supply than used
in ohmmeters measuring up to 200 megohms.
Leakage: AC or DC current flow through insulation and over its surfaces, and AC current flow
through a capacitance. Current flow is directly proportional to voltage. The insulation and/or
capacitance are thought of as a constant impedance, unless breakdown occurs.
Resistance: That property of a substance that impedes current and results in the dissipation of
power, in the form of heat. The practical unit of resistance is the ohm. Symbol = R
Trip Point: A minimum or maximum parameter set point that will cause an indication of
unacceptable performance during a run test.
Voltage: Electrical pressure, the force which causes current through an electrical conductor.
Symbol = V
To Next Page
Loading...
Need help?
General
