Chapter 8, Problem 8.1MCQ

Positive-sequence components consist of three phasors _________ with magnitudes and _________ phase displacement in positive sequence; negative- sequence components consist of three phasors with ________ magnitudes and _________ phase displacement in negative sequence; and zero-sequence components consist of three phasors with __________ magnitudes and __________ phase displacement.

To determine

To fill: The appropriate words in the given blank spaces.

Answer to Problem 8.1MCQ

The appropriate words are: equal, $120°$ , equal, $120°$ , equal, $0°$

Explanation of Solution

The method of symmetrical components is used to solve the unbalanced system. This method is also termed as three-component method. The balanced set of components are positive sequence component, negative sequence component and zero-sequence component.

Positive Sequence components: The positive-sequence system is represented by a balanced system of phasors having the same phase sequence (and therefore positive phase rotation) as the original unbalanced system. The phasors of the positive-sequence system are equal in magnitude and displaced from each other by $120°$ , as shown in figure below.

Negative Sequence components: The negative-sequence system is represented by a balanced system of phasors having the opposite phase sequence (and therefore negative phase rotation) to the original system. The phasors of the negative-sequence system are also equal in magnitude and displaced from each other by $120°$ , as shown in figure below.

Zero Sequence components: The zero-sequence system is represented by three single phasors that are equal in magnitude and angular displacement between all the phasors is $0°$ , as shown in figure below.

Therefore, in positive-sequence component, there are three phasors of equal magnitude but $120°$ displaced. In negative-sequence component, there are three phasors of equal magnitude but displaced $120°$ in negative sequence and in zero-sequence component there are three phasors of equal magnitude with $0°$ phase displacement.