Alternating Current/Motors Flashcards
Extra low voltage is classified as
30v or less
Low voltage is classified as
31v-750v
High voltage is classified as
750v or more
RMS stands for?
Root means square
RMS is also known as?
effective value
What does RMS measure?
value of the AC wave that indicates the same energy potential as an equivalent DC source
What does it mean to be “out of phase”?
When voltage wave/current reach peak values and 0 values at different points in time
What does it mean to be “in phase”
When voltage wave/current reach peak values at the same time
What is a phase angle?
Difference in degrees between one phase and another
Factors affecting inductance? (5)
- Number of turns
- coil diameter
- length of coil
- core material
- winding coil layers
Factors affecting capacitance? (2)
- Area of plates: Larger plates = Increased capacitance
- Distance between plates: Closer; increases capacitance. Further
What does a “Henry” describe?
Amount of resistance in an inductive load
What does “ICE” refer to when referencing capacitors?
Current in a capacity circuit slows voltage
In a resistive circuit, current and voltage are _______ phase
IN
In a inductive circuit, current ____ voltage by 90 degrees
lags
In a capacitive circuit, current ______ voltage by 90 degrees
leads
Transformers primary and secondary windings are not electrically connected. True or False?
True
Three basic components of a transformer are?
Prim, Sec, Core
The secondary winding on a transformer is opposite polarity of the primary. T or F?
True
Name some transformer core materials?
Air
Iron
Soft iron
Laminated steel
Name a few types of single phase transformers
control
tapped
isolation
auto
current
potential
Name the three types of power transformers
- Open Delta
- Closed Delta
- Wye (star)
An open delta power transformer reads: (2)
240v
120v
A closed delta power transformer reads: (3)
240v
208v
120v
A Wye (star) power transformer reads
208v
120v
Three main reasons for power loss in transformers?
- Resistance in windings
- Hysteresis
- Eddy currents
How to reduce eddy loss in transformer core?
Use laminated core
What is Hysteresis?
heat losses due to friction between molecules
What are eddy currents?
Losses due to current flow in core material
Voltage imbalance may be within __%
2%
Current imbalance may be within ___%
10%
Short to ground is read as ____ or ___ resistance
low or no
CSIR motor does not have a ______ capacitor and becomes a ____ motor when the potential relay drops out
start
PSC
What is the acronym to remember when dealing with potential start relays?
5,2,1
Can She Run?
Normally closed contacts on a potential relay are located between __ and __ contacts
1 and 2 contacts
Locked rotor amps is __ times the RLA/FLA
6 times
RLA/FLA is ___ of the LRA
1/6
