Transformers and AC Circuits

Table of Contents

Chapter 1: Principles of Alternating Current

Topics: AC and DC electricity; AC waveform; Peak-to-peak, average, effective values; Energy storage; Faraday's Law; Basic circuit concepts

Learning Objectives:

• State of definition of a waveform.
• Demonstrate how to calculate the frequency of an alternator's output.
• Explain how to calculate an effective value.
• Name the kinds of values that must be used when applying the dc rules and laws to ac circuits.

Chapter 2: Mathematics in AC Circuits

Topics: Potential difference; Angles and degrees; Vectors applied to AC circuits; Graphic and math solutions; Calculating instantaneous values

Learning Objectives:

• Describe a triangle.
• State the definition of a vector.
• Identify the vector representing resistance in a vector diagram.
• Demonstrate how to calculate the total impedance in an ac circuit.

Chapter 3: Inductance and Inductive Reactance

Topics: Factors affecting inductance; CEMF; Inductive reactance and time delay; Phase angles; Impedance; Mutual induction; Inductors

Learning Objectives:

• Name the property of a coil that makes it resist changes in current.
• List the factors that determine inductance in a coil.
• State the definition of counter electromotive force.
• Demonstrate how to convert a frequency in Hz to a frequency in radians per second.

Chapter 4: Capacitance and Capacitive Reactance

Topics: How a capacitor works; Factors controlling capacitance; Kinds of capacitors; Time constants; Capacitive reactance; Phase angle

Learning Objectives:

• Name the parts of a capacitor.
• List the factors that affect the amount of charge stored in a capacitor at a given potential difference.
• Demonstrate how to install a multisection electrolytic capacitor.
• State the definition of capacitive reactance.

Chapter 5: Impedance

Topics: Impedance in series circuits; Phase angles; Resonance in series circuits; Impedance in parallel circuits

Learning Objectives:

• State the definition of impedance
• Explain how to calculate the impedance in a series ac circuit.
• Demonstrate how to find the value of a phase angle for a circuit.
• Explain how to calculate the impedance in a parallel circuit.

Chapter 6: Power and Energy in AC Circuits

Topics: Work and energy; Power in resistive, inductive, and capacitive circuits; Power factor correction; Power capacitors; Capacitor installation

Learning Objectives:

• State the definition of power.
• Demonstrate how to calculate power in an inductive circuit.
• State the reason why capacitors are added to circuits to increase the power factor.
• Explain how to install capacitors correctly.

Chapter 7: Three-Phase Circuits

Topics: Three-phase alternators; Y- and delta-connected alternators; Power in three-phase circuits; Load connections; Measuring power

Learning Objectives:

• List the main advantages of the three-phase ac system.
• State the definition of phase sequence.
• Demonstrate how to calculate the RMS power in a single-phase circuit.
• Explain how to measure the total power consumed by the load in a three-phase circuit.

Chapter 8: Principles of Transformers

Topics: Magnetic field; No-load operation; Transformer construction, losses, and efficiency; Autotransformers; Instrument transformers

Learning Objectives:

• Explain the difference between the primary winding and the secondary winding in a transformer.
• Explain how the windings are positioned in a core-type transformer.
• List the kinds of losses that occur in transformers.
• State the definition of a current transformer.
• List the functions of an instrument transformer.

Chapter 9: Transformer Applications

Topics: Transformer designation, insulation, cooling, and polarity; Single- and three-phase transformer connections; Installing transformers

Learning Objectives:

• Name general kinds of transformers.
• List the temperature limits for each class of transformer insulation.
• Explain how oil-immersed transformers are cooled.
• Name the common methods of connecting three single-phase transformers for three-phase operation.
• Explain how to select the correct location for a transformer.

Chapter 10: Maintaining Transformers

Topics: Preventive maintenance; Inspection; Transformer liquids; Transformer failure; Testing; Disassembly and inspection

Learning Objectives:

• Explain what to look for during an inspection of sealed transformers.
• List problems that are indicated by an increase in transformer operating temperature.
• Demonstrate how to perform a breakdown test.
• Explain how to locate the exact point of a leak in a welded joint below the liquid level.
• List the steps in inspecting a transformer when a winding fails.

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