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Questions and Answers
What is the primary purpose of stepping up voltage in power transmission using a transformer?
What is the primary purpose of stepping up voltage in power transmission using a transformer?
- To stabilize the frequency.
- To increase current and reduce power losses.
- To increase current and step down voltage for end-users.
- To reduce current and minimize power losses. (correct)
A transformer's primary and secondary windings are electrically isolated but magnetically linked. What facilitates the transfer of energy between the windings?
A transformer's primary and secondary windings are electrically isolated but magnetically linked. What facilitates the transfer of energy between the windings?
- Resistive coupling
- Direct current flow
- Capacitive coupling
- A fluctuating magnetic field. (correct)
What determines whether a transformer is considered a step-up or step-down transformer?
What determines whether a transformer is considered a step-up or step-down transformer?
- The ratio of turns in the primary and secondary windings (correct)
- The input frequency
- The core material used
- The type of insulation
In an ideal transformer, which of the following assumptions is made?
In an ideal transformer, which of the following assumptions is made?
Why can't a standard transformer operate with a DC (direct current) input?
Why can't a standard transformer operate with a DC (direct current) input?
What happens to the transformer if the applied voltage is too high?
What happens to the transformer if the applied voltage is too high?
In a transformer, what does the 'turns ratio' ($N_1/N_2$) primarily define?
In a transformer, what does the 'turns ratio' ($N_1/N_2$) primarily define?
During no-load condition in a real transformer, what constitutes the input current?
During no-load condition in a real transformer, what constitutes the input current?
In a transformer operating at no load, the current $I_0$ is composed of which two components?
In a transformer operating at no load, the current $I_0$ is composed of which two components?
If $E_1$ and $E_2$ are the primary and secondary induced EMFs in a transformer, and $N_1$ and $N_2$ are the number of turns in the primary and secondary windings respectively, what is the relationship between $E_1$, $E_2$, $N_1$, and $N_2$?
If $E_1$ and $E_2$ are the primary and secondary induced EMFs in a transformer, and $N_1$ and $N_2$ are the number of turns in the primary and secondary windings respectively, what is the relationship between $E_1$, $E_2$, $N_1$, and $N_2$?
Flashcards
Transformer
Transformer
A static device that transfers AC from one circuit to another at a constant frequency.
Step-Up Transformer
Step-Up Transformer
Increases the voltage from primary to secondary winding, decreasing current.
Step-Down Transformer
Step-Down Transformer
Decreases the voltage from primary to secondary winding, increasing current.
Turns Ratio
Turns Ratio
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Transformation Ratio (k)
Transformation Ratio (k)
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Ideal Transformer
Ideal Transformer
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Transformer on DC
Transformer on DC
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EMF Equation
EMF Equation
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Transformer at No Load
Transformer at No Load
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No-Load Current (Iâ‚€)
No-Load Current (Iâ‚€)
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Study Notes
- Single-phase transformers transfer AC from one circuit to another at a constant frequency.
Step Up Transformers
- Voltage increases while current decreases.
Step Down Transformers
- Voltage decreases while current increases.
- Voltage is raised to reduce losses from the generator to the user.
Transformer Applications
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Adjust voltage and current levels to suit specific needs.
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Isolate circuits.
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Primary and secondary windings are connected to the source/load.
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The number of windings determines whether it's a step-up or step-down transformer.
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The relationship between primary and secondary windings is based on magnetic flux or electromotive force (EMF).
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Alternating Current (AC) is required.
Turns Ratio
- Defined as N1/N2.
Transformation Ratio (k)
- k = E2/E1 = N2/N1
Ideal Transformer
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Only magnetic flux between the coils.
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Efficiency is 100%.
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Has very high magnetic permeability.
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E2/E1 = N2/N1
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E2 * I2 * cos(Φ) = E1 * I1 * cos(Φ)
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In circuits, the current lags the voltage by 90 degrees.
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No change in frequency when using direct current.
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The changing magnetic flux doesn't allow for any conversion.
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High voltage overheats the transformer coils, causing them to burn.
EMF Equation
- Average rate of change of flux = 4fΦm wb/s
- Average EMF induced per turn = 4fΦm Volts
- RMS value = 1.11 x 4fΦm = 4.44fΦm Volts per turn
- To divide the actual value by total coils depending on secondary and primary coils
- E1 = N1 * (4.44 f Φm)
- E2 = N2 * (4.44 f Φm)
- k can be calculated as: K = E2/E1 = N2/(4.44fΦm) / N1/(4.44fΦm) = N2/N1
Core Type Transformer
- E1/N1 = E2/N2
Transformer at No Load (Open Circuit)
- The output has no load.
- There is power loss and cannot neglect it.
- I0 is 2% to 10% of the value of per current.
No Load conditions
- Iw = I0 * cos(Φ)
- Imag = I0 * sin(Φ)
- I0 = sqrt(Iw^2 + Imag^2)
- cos(Φ) = Iw / I0
- P. = V * I. * cos(Φ)
- R. = V / Iw
- X. = V / Imag
- Includes exciting resistance
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