Introduction to transformers Flashcards
The process of producing a voltage by the interaction of magnetic fields and a conductor
Induction
The property of a circuit that opposes change in current
Inductance
When a change in current in one circuit causes a voltage to be induced into another circuit
mutual induction
a Transformer transfers energy from one AC circuit to another through…
Electromagnetic Induction
The secondary AC Frequency will be the ________ as the Primary AC frequency
same
The magnetic circuit of a transformer is usually a path of
low reluctance
Two Common Core losses are?
Eddy currents and hysteresis
Transformer cores are constructed with this material to prevent hysteresis?
Silicon steel
What is done to reduce transformer eddy currents
The core is constructed with thin laminted steel and coated with varnish to insulated them from on another
Three basic types of transformer construction are?
Core typed, Shell type and H type
Which type of transformer has the least leakage flux?
The H-type.
Transformers usually have an efficiency of ?
95 % to 98%
The unwanted current flow induced in a core producing heat (power losses) is called?
Eddy currents
Magnetic flux lines that are established outside the core and windings that constitute a small amount of lost energy
leakage flux
Basic transformer name plates indicate
primary voltage, secondary voltage, VA or KVA rating
The capacity of a transformer is rated in
KVA or VA
Other information that may be on a transformer nameplate
frequency, temperature rise, percent impedance, type of insulating oil, serial number, type number and single or three phase.
The transformer winding that is connected to the input voltage or energy source
Primary winding
The transformer winding that is connected to the load
Secondary winding
A transformer name plate does not list this rating.
Current, (Current is calculated using the KVA and Voltage)
The percent impedance of a transformer is used to calculate?
transformer losses, voltage regulation and system short circuit currents
The impedance of a transformer is affected by
The amount and type of core, winding wire size, number of winding turns and degree of magnetic coupling
This test is done to determine a transformers percent impedance after manufacturing.
A short circuit test
Transformers are used for these 3 applications
- step up voltage of a circuit 2.step down the voltage of a circuit 3. isolate on circuit from amother
