Class Flashcards
The simplest circuit breaker is
The ordinary knife switch
This type of circuit breaker the arc is extinguished by a blast of air
Air blast breakers
In oil circuit breakers, the arch originates in oil, but the heat of the ark immediately evaporates the surrounding oil this causes
The oil to disassociate into carbon and a substantial volume of gas is hydrogen, high-pressure the hydrogen, then suffocates the ark
With the nerve gas breakers, the gas will liquefy so right away that it must be kept heated if
It must be kept heated, so it doesn’t liquefy if it is to be used outdoors
Why is the speed of a circuit breaker desirable?
So that it can minimize the arc , protect itself and protect everything around it
List the three main circuit breaker ratings
Breaker voltage, continuous current, interrupting current
A circuits interrupting time is
The rating that gives you the amount of time it takes to open
Three trip free power circuit breakers are
Electrical, mechanical pneumatic
The four types of insulating media in circuit breakers are
Air type, oil type, gas type, and vacuum type
In a wye connected system, the line voltage is higher than the phase voltage by
A factor of the square root of three or 1.732
Three phase voltages are 120° out of
Out of phase with each other, not in phase with each other
The line current of a delta connection is higher than the phase current by
A factor of the square root of three or 1.732
A magnetically operated machine that can change values of voltage current and impedance without a change of frequency is
A transformer
The efficiency among transformers commonly range from
90 to 99%
All values of a transformer are
Proportional to its turn ratio
The ratio of the amount of turns in the primary winding compared to the amount of turns in the secondary whining is
The turns ratio
The transformer with the secondary winding is physically an electrically isolated from the primary whining is
An isolation transformer
When a coil induces a voltage into itself, it is known as
Self induction
The ability of one coil to induce voltage into another coil is
Called mutual induction
A transformer with one winding that is used for both primary and secondary is
An auto transformer
What are the three functions of transformer oil
The oil provides electric insulation between the windings and the case it is also used to help provide cooling and to prevent the formation of moisture
Name the phenomenon detrimental to the success of the power circuit breaker
The plasma arc
What is the primary function of the power circuit breaker?
Protection
What are harmonics and when do they occur?
Harmonics are voltages or currents that operate at a frequency that is a multiple of the fundamental power frequency. They occur at the second harmonic that would be 120 Hz or further multiples.
