Unit 27 Industrial maintenance
Three phase transformer ratings are _____ greater than single-phase transformers -
answer150%
The power fails _______ during each cycle - answer3 times
In a balanced three-phase system, the conductors need be only about ____ the size of
conductors for a single phase - answer75%
If three separate coils are spaced 120 degrees apart, then three voltage are -
answer120 degrees out of phase
Wye - answermade by connecting one end of each of the three-phase windings
together
phase voltage - answervoltage measured across a single winding
line voltage - answervoltage measured between the lines
In a wye connected system phase current and line current are - answerthe same
E (line) - answerE (phase) x 1.732
E (phase) - answerE (line)/ 1.732
VA line - answer1.732 x E (line) x I (line)
VA phase - answer3 x E (phase) x I (phase)
P (line) - answer1.732 x E (line) x I (line) x PF
P (phase) - answer3 x E (phase) x I (phase) x PF
VARs(c) - answer1.732 x E( line) x I (line)
VA - answerP/PF
PF - answerP/VA
VARs - answersquare root( VA^2-P^2)
Three phase transformer ratings are _____ greater than single-phase transformers -
answer150%
The power fails _______ during each cycle - answer3 times
In a balanced three-phase system, the conductors need be only about ____ the size of
conductors for a single phase - answer75%
If three separate coils are spaced 120 degrees apart, then three voltage are -
answer120 degrees out of phase
Wye - answermade by connecting one end of each of the three-phase windings
together
phase voltage - answervoltage measured across a single winding
line voltage - answervoltage measured between the lines
In a wye connected system phase current and line current are - answerthe same
E (line) - answerE (phase) x 1.732
E (phase) - answerE (line)/ 1.732
VA line - answer1.732 x E (line) x I (line)
VA phase - answer3 x E (phase) x I (phase)
P (line) - answer1.732 x E (line) x I (line) x PF
P (phase) - answer3 x E (phase) x I (phase) x PF
VARs(c) - answer1.732 x E( line) x I (line)
VA - answerP/PF
PF - answerP/VA
VARs - answersquare root( VA^2-P^2)
