PHEP Chapter 18 Flashcards
why are delta wye connections desired
to provide path for 3rd harmonic magnetizing current
when can 3 phase power still be carried when one of the single phase units is removed from service?
delta delta transformer
in which connection does line voltage equal 1.73 times phase voltage?
wye connection
what is true in a delta connection?
line voltage equals phase voltage
line current equals 1.73 times phase current
what is residual current
current left over when vectorial sum of 3 phase currents is zero
in any 3 phase circuit what is equal to the apparent power
1.73 times line current times line voltage
what happens when VARS are out
current will lag voltage
impedance will consist of resistance and inductive reactance
what is the most commonly used cell in batteries
lead cell
what are the active parts of the plates in a lead cell
lead peroxide and sponge lead
electrolyte is sulfuric acid
during their chemical reaction what do the components of a lead cell create
lead sulphate
how many more plates does the negative electrode have than the positive plate
1
what is the open circuit voltage of a fully charged commercial lead cell
2.07
what happens when the voltage and specific gravity curves level off while charging takes place
gassing rises
how do you prevent violent bubbling when charging
reduce charging current
what are control bus batteries used for
control equipment, station auxilleries, alarm, light systems
