Skip to main content

300x250 Ads

Phasor Diagram for Synchronous Generator

By Ashik

In the present article we are going to discuss one of the easiest methods of making the phasor diagram for synchronous generator. Now let us write the various notations for each quantity at one place, this will help us to understand the phasor diagram more clearly. In this phasor diagram we are going to use:
Ef which denotes excitation voltage
Vt which denotes terminal voltage
Ia which denotes the armature current
θ which denotes the phase angle between Vt and Ia
á´ª which denotes the angle between the Ef and Ia
δ which denotes the angle between the Ef and Vt
ra which denotes the armature per phase resistance
In order to draw the phasor diagram we will use Vt as reference .Consider these two important points which are written below:
(1) We already know that if a machine is working as a synchronous generator then direction of Ia will be in phase to that of the Ef.
(2) Phasor Ef is always ahead of Vt.
These two points are necessary for making the phasor diagram of synchronous generator. Given below is the phasor diagram of synchronous generator:
In this phasor diagram we have drawn the direction of the Ia is in phase with that of the Ef as per the point number 1 mentioned above. Now let us derive expression for the excitation emf in each case. We have three cases that are written below:
(a) Generating operation at lagging power factor
(b) Generating operation at unity power factor
(c) Generating operation at leading power factor
Given below are the phasor diagrams for all the operations.
phasor diagram of synchronous generator
(a) Generating operation at lagging power factor: We can derive the expression for the Ef by first taking the component of the Vt in the direction of Ia. Component of Vt in the direction of Ia is VtcosΘ, hence the total voltage drop is (VtcosΘ+Iara) along the Ia. Similarly we can calculate the voltage drop along the direction perpendicular to Ia. The total voltage drop perpendicular to Ia is (Vtsinθ+IaXs). With the help of triangle BOD in the first phasor diagram we can write the expression for Ef as
E_f^2=(V_tcos\theta +I_a\times r_a)^2+(V_tsin\theta +I_a\times X_s)^2

(b) Generating operation at unity power factor: Here also we can derive the expression for the Ef by first taking the component of the Vt in the direction of Ia. But in this case the value of theta is zero and hence we have ᴪ=δ. With the help of triangle BOD in the second phasor diagram we can directly write the expression for Ef as







c) Generating operation at leading power factor: Component in the direction of Ia is VtcosΘ. As the direction of Ia is same to that of the Vt thus the total voltage drop is (VtcosΘ+Iara). Similarly we can write expression for the voltage drop along the direction perpendicular to Ia. The total voltage drop comes out to be (Vtsinθ-IaXs). With the help of triangle BOD in the first phasor diagram we can write the expression for Ef as
E_f^2=(V_tcos\theta +I_a\times r_a)^2+(V_tsin\theta -I_a\times X_s)^2E_f^2=(V_t+I_a\times r_a)^2+(I_a\times X_s)^2
Labels:

Comments

Post a Comment

Popular posts from this blog

Armature Winding ,Pole Pitch, Coil Span, Commutator Pitch

By Ashik
Now we are going to discuss about armature winding in details. Before going through this section, we should understand some basic terms related to armature winding of dc generator . Pole Pitch Definition of Pole Pitch The pole pitch is defined as peripheral distance between center of two adjacent poles in dc machine. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. This is naturally equal to the total number of armature slots divided by number of poles in the machine. If there are 96 slots on the armature periphery and 4 numbers of poles in the machine, the numbers of armature slots come between two adjacent poles centers would be 96/4 = 24. Hence, the pole pitch of that dc machine would be 24. As it is seen that, pole pitch is equal to total numbers of armature slots divided by total numbers of poles, this can alternatively referred as armature slots per pole . Coil Span or Coil Pitch Coil of
Post a Comment
Read more

Coding

By Ashik
Binary Coding 1. Binary Coded Decimal (BCD) Binary coded decimal (BCD) is a way to express each of the decimal digits with a binary code. There are only ten code groups in the BCD system, so it is very easy to convert between decimal and BCD. Because welike to read and write in decimal, the BCD code provides an excellent interface to binary systems. Examples of such interfaces are keypad inputs and digital readouts. The 8421 Code: The 8421 code is a type of BCD (binary coded decimal) code. Binary coded decimal means that each decimal digit, 0 through 9, is represented by a binary code of four bits. The designation 8421indicates the binary weights of the four bits 2 3 , 2 2 , 2 1 , 2 0 . The ease  of conversion between 8421 code numbers and the familiar decimal numbers is the main advantage of this code.  All wehave to remember are the ten binary combinations that represent the ten decimal digits as shown in Table 1. The 8421 code is the predominant BCD code, and when we ref
Post a Comment
Read more

Propagation-Radio-Waves

By Ashik
Radio Wave Propagation types
Post a Comment
Read more

Add