Transformer Step-Down Ratios Quiz

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Questions and Answers

What is the voltage ratio of a transformer with a primary voltage of 30 V and a secondary voltage of 90 V?

$rac{30}{90}$

$rac{90}{30}$

$3$ (correct)

$rac{1}{3}$

What is the name of a transformer where the voltage across the secondary is less than the voltage across the primary?

Voltage ratio transformer

Proportional transformer

Step-down transformer (correct)

Step-up transformer

What is the ratio of a four-to-one step-down transformer?

6:1

1:6

4:1 (correct)

1:4

What type of transformer has fewer turns in the primary than in the secondary?

Step-up transformer Signup and view all the answers

What is the name of a transformer where the voltage across the secondary is greater than the voltage applied to the primary?

Step-up transformer Signup and view all the answers

What is the correct way to write the ratio of a one-to-four step-up transformer?

1:4 Signup and view all the answers

What is the main difference between an IDG and a CSD?

An IDG contains both the CSD and the AC generator in the same housing, while a CSD does not. Signup and view all the answers

What is the purpose of the 'generator' term being used for IDGs, even though they are actually brushless alternators?

It is a historical term that has not been updated. Signup and view all the answers

What is the main advantage of AC motors compared to DC motors?

AC motors require less maintenance due to the lack of brushes and commutators. Signup and view all the answers

Which of the following is a method of producing a rotating field in an AC motor?

Capacitor Signup and view all the answers

What is the relationship between the primary and secondary voltages in a step-up transformer?

The secondary voltage is greater than the primary voltage. Signup and view all the answers

What is the relationship between the primary and secondary turns in a step-down transformer?

The primary has more turns than the secondary. Signup and view all the answers

What is the primary function of the permanent magnetic field in a brushless alternator?

To provide the initial magnetic flux to start the generator Signup and view all the answers

What is the purpose of the generator control unit (GCU) in a brushless alternator?

To rectify the AC output from the armature and supply it to the exciter field winding Signup and view all the answers

What is the role of the six silicon diodes in a brushless alternator?

To rectify the DC output from the exciter output winding and supply it to the output field winding Signup and view all the answers

Which of the following components in a brushless alternator rotate as a unit?

The permanent magnet, exciter output winding, six diodes, and output field winding Signup and view all the answers

What is the purpose of the laminated frame in the alternator housing?

To house the three-phase output stator windings Signup and view all the answers

In a brushless alternator, which component induces voltage into the main output coils?

The output field winding Signup and view all the answers

What are the two mechanical parts that all generators must have for relative motion to take place between the conductor and the magnetic field?

Stator and rotor Signup and view all the answers

In a DC generator, which part is always the armature?

The rotor Signup and view all the answers

In an alternator, which part may be the armature?

Both the rotor and the stator Signup and view all the answers

What is the main difference between a revolving-armature alternator and a DC generator?

The alternator generates AC, while the DC generator generates DC Signup and view all the answers

What is the main advantage of the revolving-field type alternator over the revolving-armature type?

It is used almost exclusively in aircraft Signup and view all the answers

What is the total circuit resistance in the given example?

$24 \Omega$ Signup and view all the answers

What is the circuit current in the given example?

$1 A$ Signup and view all the answers

What is the power dissipated in the source in the given example?

$6 W$ Signup and view all the answers

What is the power dissipated in the load in the given example?

$18 W$ Signup and view all the answers

According to the maximum power transfer graph summary, in which region should the load resistance be less than the source resistance?

Region 1 Signup and view all the answers

What is the formula for calculating the turns ratio of a transformer used for impedance matching?

$T^2 = \frac{Z_P}{Z_S}$ Signup and view all the answers

Study Notes

Transformers

A transformer with a turn ratio of 6:1 means the primary has 6 times the number of turns as the secondary.
A step-down transformer has a lower voltage across the secondary than the primary, with a ratio written as 4:1.
A step-up transformer has a higher voltage across the secondary than the primary, with a ratio written as 1:4.
The voltage ratio of a transformer is the ratio of the primary voltage to the secondary voltage (VS/VP).

IDG (Integrated Drive Generator)

An IDG is a type of generator that contains a CSD (Constant Speed Drive) and an AC generator in the same housing.
IDGs are actually brushless alternators, despite being called generators.

AC Motors

Advantages of AC motors include lower cost and less maintenance due to the lack of brushes and commutators.
Methods of speed control and direction of rotation will be described.
Rotating fields can be produced using capacitors, inductors, or shaded or split poles.

Brushless Alternator

A brushless alternator has a permanent magnetic field, an exciter field, and a main output field.
The permanent magnets start the generator, producing an output before field current flows.
The magnetic field induces voltage into an armature, which is sent to the generator control unit (GCU).
The GCU rectifies the AC and sends it to the exciter field winding.

AC Motor Theory

AC motors can be synchronous or induction motors, and can be single-phase or polyphase.
Synchronous motors have a rotor and a stator, with the rotor rotating and the stator remaining stationary.
Induction motors have a rotating field that induces voltage into the stator.

Alternators

Alternators can be revolving-armature or revolving-field type.
Revolving-armature alternators have a rotor that is the armature and a stator that is the field.
Revolving-field alternators have a rotor that is the field and a stator that is the armature, commonly used in aircraft.

Power Transfer and Impedance Matching

Maximum power transfer occurs when the load resistance equals the source resistance.
Minimum heat generated in the source occurs when the load resistance is less than the source resistance.
Impedance matching is important for connecting sources and loads of dissimilar impedance, and can be done using a transformer.
Transformers can be used to match impedances without losing power.

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Description

Test your knowledge on step-down transformer ratios and voltage calculations. Learn how to determine the number of turns in the primary and secondary sides based on the given ratio.