DEFINITIONS - CONT - TM-55-1905-223-24-40312

TM 55-1905-223-24-4

GLOSSARY - CONT

DEFINITIONS - CONT

INSULATION

A non-conductive material such as rubber or plastic intended to prevent

current from flowing. Technically, insulation is any material which

resists the flow of current.

INSULATION RESISTANCE

A measure of the ability of insulation to prevent current from flowing. A

megohmmeter is used to measure the resistance in millions of ohms

between the windings and metal frame of a generator to determine the

insulation resistance of the windings.

ISOCHRONOUS

As it applies to engine governors, maintaining constant steady-state

speed regardless of the load within the rating of the engine. Thus, a

generator set is said to be isochronous if the frequency remains the

same regardless of load.

LINE-TO-LINE-VOLTAGE

The voltage between any two phases of a multiphase system.

A high range high voltage ohmmeter. By measuring the current flow

caused by the applied voltage, insulation resistance can be determined.

OHM

The unit of measure of electrical resistance. One ohm of resistance will

allow a current of one ampere to flow with an applied potential of one

volt.

An instrument for measuring electrical resistance.

PARALLEL OPERATION

The method by which two or more generators having the same voltage

and frequency characteristics are connected to a common load.

PHASE

The windings or an ac generator into which a voltage is induced. In a

three-phase system, there are three sets of windings, each set having a

voltage alternating within it exactly one-third of a cycle after the one

ahead of it because of the physical arrangement of the coils.

PITTING

Corrosion attack in localized areas, resulting in the formation of tiny

cavities.

Glossary 5