30 Questions
In a three-phase system, what is the angular displacement between the induced voltages in the coils?
120 degrees
What type of system is produced by a generator (alternator) with windings or coils placed 120 degrees apart?
Polyphase system
How many separate windings or coils are there in a three-phase generator?
3
What is the function of the rotor in a three-phase alternator?
Rotates and creates a magnetic field
What do the terminals a-a', b-b', and c-c' represent in a three-phase system?
Different coils
What allows a three-phase generator to supply power to both single-phase and three-phase loads?
Equal induced voltages in all coils
What is one of the main advantages of three-phase systems over single-phase systems?
Reduced energy losses during transmission
How many phases are typically used in electric power generation and distribution?
Three phases
What industry requires 48 phases for melting purposes?
Aluminum industry
In three-phase power generation, why are one-phase or two-phase inputs often taken from the three-phase system?
To avoid generating them independently
How do three-phase systems compare to single-phase systems for the same amount of power?
More economical
What is a key advantage of using three-phase systems in terms of distributing power to balanced loads?
Minimizing voltage imbalances and reducing stress on the electrical system
Why is three-phase power transmission considered more efficient over long distances?
Reduced wiring requirements
How can three-phase systems be designed to improve power factor according to the text?
By increasing power factor which is important for optimizing power usage
Why is it advantageous for many industrial equipment to operate on three-phase power?
Simplifying installation and operation by ensuring compatibility with the equipment
What characteristic of three-phase systems results in uniform power transmission and less vibration of machines?
Instantaneous power being constant, not pulsating
In a balanced Y-Y system, what do the phase voltages represent?
Line-to-neutral voltages
How do balanced loads in three-phase systems affect the distribution of power among phases?
Ensure that the power drawn from each phase is equal
How does the amount of wire required for a three-phase system compare to that required for an equivalent single-phase system?
The amount of wire required is less for a three-phase system
What is ZY in a Y-Y circuit referred to as?
Total load impedance per phase
Which component's impedance is Zn in a Y-Y circuit?
Impedance of the neutral line
What is the line current for phase A in the Y-Y system?
6.81∠-21.8° A
Which component's impedance is Zs in a Y-Y circuit?
Internal impedance of the generator
In a balanced Y-Y system, what can be assumed if no source or line impedance is given?
ZY = ZL
What is ZL in a Y-Y circuit?
Impedance of each phase of the load
What is the value of Vcn in Problem 1, assuming a positive sequence?
110∠90° V
What is the impedance of the Y-connected balanced load in Problem 2?
24∠19° per phase
Based on the positive sequence of source voltages, what is the line current for phase B?
6.81∠141.8° A
In the three-wire Y-Y system, which phase has a line current of 6.81∠141.8° A?
Phase B
If the source voltages in the Y-Y system were not in positive sequence, what would happen to the line currents?
They would change both magnitude and phase angle
This quiz is focused on three-phase circuits, specifically addressing Wye-Wye connections. Topics covered include the introduction to three-phase circuits and analyzing systems with AC sources at the same frequency but different phases.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
