Unit 22 Flashcards
What is used to reduce losses because of eddy currents in transformers? and what is used to separate them?
Long laminated iron cores ; insulation (usually lacquer)
The relationship of the primary winding voltage to the secondary winding voltage is the same as the relationship between the ________ on the primary as compared to the ________ on the secondary
Number of turns ; Number of turns
This device has the ability to transfer electrical energy from one system to another, with no physical connection between the two systems
Transformer
1 kilovolt-ampere = how many VA?
1,000
What do you call the energy required to realign the core molecules to the changing electromagnetic field in a transformer?
Hysteresis Loss
Conductor resistance is directly proportional to the ____ of a conductor and inversely proportional to the _____ of a conductor
Length ; Cross Sectional Area
The voltage level that can be induced in the secondary winding, form the primary magnetic field, is a function of the number of secondary conductor loops (turns) that are ____ by the primary electromagnetic field
Cut
What is the main purpose of an autotransformer?
Step voltage up or down
The energy transfer of a transformer is accomplished because the ______ lines of force from the primary winding induce a _____ in the secondary wnding
Electromagnetic ; Voltage
Autotransformers use a common _____ for both the primary and secondary.
Winding
The induced voltage in each loop of the secondary winding is dependent on the number of secondary conductor loops as compared to what?
The number of primary turns
The secondary winding of a step-down transformer has ____ turns than the primary winding.
Fewer
As current flows through the transformer, the iron core is temporarily ____ by the electromagnetic field created by the alternating current
Magnetized
The heating from harmonic currents is _______ to the square of the harmonic current
Proportional
The primary winding in a transformer is connected to the _____ and the secondary winding is connected to the _____
Voltage source ; Load
The disadvantage of an autotransformer is the lack of ____ between the primary and secondary conductors.
Isolation
Voltage induced in the secondary winding of a transformer is equal to the sum of what?
Voltages induced in each loop of the secondary winding
When a load is connected to the secondary of a transformer, secondary voltage induced from the primary magnetic field will cause _____ to flow through the secondary conductor wiinding
Current
Three-phase, 4-wire, wye-connected systems that supply nonlinear line-to-neutral loads can ______ because of circulating odd triplen ______ currents.
Overheat ; Harmonic
What is the formula for calculating a single-phase transformers primary and secondary current rating?
I = VA / E
The _____ lines from the secondary magnetic field effectively reduce the strength of the primary flux lines, and as a result, less CEMF is generated in the primary winding conductors.
Flux
The secondary current flow in the secondary winding creates an ______ field that opposes the primary electromagnetic field
Electromagnetic
Name four types of power losses that occur in transformers
Conductor Resistance ; Hysteresis ; Eddy Currents ; Flux Leakage
What is the formula for calculating a three-phase transformers primary and secondary current rating?
I = VA / (E x 1.732)
