Transformers Level 2 Study Guide
questions and answers
What is an electrostatic shield or isolation transformer? ✔✔Helps prevent common-mode noise
from transferring from the transformer's primary to the secondary
What is the main limitation of an autotransformer? ✔✔Has a lower impedance than a two
winding transformer, which allows higher short circuit currents.
What is the formula for CO-Ratio? ✔✔(HV-LV) / HV
What is autotransformer reduced voltage starter? ✔✔Utilizes taps at 50%, 65% and 80% to start
large horsepower motors.
What is three phase power? ✔✔Type of power and phases utilities generate.
What is a generator? ✔✔Machine that converts mechanical energy into electrical energy by
means of electromagnetic induction.
What is a synchroscope? ✔✔Device that indicates whether two AC sources to be connected in
parallel are in the correct phase relationship
, What factors determine the amount of voltage produced by a generator? ✔✔The strength of the
magnetic field, speed of rotation and number of turns.
What is a Reactor? ✔✔A coil added in series with a load to reduce inrush current, voltage
notching effects, and voltage spikes.
Define Saturable Core reactor ✔✔inductor whose inductance is controlled through the use of a
magnetic field crated by a second winding wound around the same iron core as the primary
winding.
Define Noch ✔✔Distortion in a voltage waveform where the voltage quickly drops toward zero
and then returns to the correct value.
Define Common Mode Noise ✔✔type of electromagnetic interference induced on power of
communications lines.
Define Harmonics ✔✔Voltage or current at a frequency that is an integer of the fundamental
frequency.
Inrush Current ✔✔Instantaneous high input current drawn by a power supply or electrical
equipment at turn-on.
What are the two common types of reactors? ✔✔Dry type
questions and answers
What is an electrostatic shield or isolation transformer? ✔✔Helps prevent common-mode noise
from transferring from the transformer's primary to the secondary
What is the main limitation of an autotransformer? ✔✔Has a lower impedance than a two
winding transformer, which allows higher short circuit currents.
What is the formula for CO-Ratio? ✔✔(HV-LV) / HV
What is autotransformer reduced voltage starter? ✔✔Utilizes taps at 50%, 65% and 80% to start
large horsepower motors.
What is three phase power? ✔✔Type of power and phases utilities generate.
What is a generator? ✔✔Machine that converts mechanical energy into electrical energy by
means of electromagnetic induction.
What is a synchroscope? ✔✔Device that indicates whether two AC sources to be connected in
parallel are in the correct phase relationship
, What factors determine the amount of voltage produced by a generator? ✔✔The strength of the
magnetic field, speed of rotation and number of turns.
What is a Reactor? ✔✔A coil added in series with a load to reduce inrush current, voltage
notching effects, and voltage spikes.
Define Saturable Core reactor ✔✔inductor whose inductance is controlled through the use of a
magnetic field crated by a second winding wound around the same iron core as the primary
winding.
Define Noch ✔✔Distortion in a voltage waveform where the voltage quickly drops toward zero
and then returns to the correct value.
Define Common Mode Noise ✔✔type of electromagnetic interference induced on power of
communications lines.
Define Harmonics ✔✔Voltage or current at a frequency that is an integer of the fundamental
frequency.
Inrush Current ✔✔Instantaneous high input current drawn by a power supply or electrical
equipment at turn-on.
What are the two common types of reactors? ✔✔Dry type
