Skip to main content

Synchronization With Infinite Bus Bar

There is a specific procedure of connecting synchronous machine to infinite bus bars. Infinite bus bar is one which keeps constant voltage and frequency although load varies. The Fig. 1 shows a synchronous machine which is to be connected to the bus bars with the help of switch K.
        If the synchronous machine is running as a generator then its phase sequence should be some as that of bus bars. The machine speed and field current is adjusted in such a way so as to have the machine voltage same as that of bus bar voltage. The machine frequency should be nearly equal to bus bar frequency so that the machine speed is nearer to synchronous speed.
Fig. 1

        When the above conditions are satisfied, the instant of switching for synchronization should be determined. This can be determined by lamps dark method, Lamps bright and dark method or by using synchroscope.
       Once switch K is closed, the stator and rotor fields of the machine lock into each other and the machine then runs at synchronous speed. The real power exchange with the mains will be now governed by the loading conditions on the shaft while the reactive power exchange will be determined by field excitation.
      The same procedure is to be followed for synchronizing the synchronous motor to the infinite bus bars. The motor is run by an auxiliary device such as small dc or induction motor initially and then synchronized to the bus bars.
       As we know that the synchronous motors are not self starting hence if switch K is closed when rotor is stationary, the average torque will be zero as the two fields run at synchronous speed relative to each other so the motor fails to start. They are made self starting by providing short circuited bars on the rotor which produce torque as produced in case of induction motors.
Labels:

Comments

Post a Comment

Comment Policy
We’re eager to see your comment. However, Please Keep in mind that all comments are moderated manually by our human reviewers according to our comment policy, and all the links are nofollow. Using Keywords in the name field area is forbidden. Let’s enjoy a personal and evocative conversation.

Popular posts from this blog

Practical Commutation

The e.m.f. induced in each coil of armature is alternating in nature. If load is connected, the current flowing will also be alternating. But the flow of current in a d.c. generator must be undirectional. This can be achieved by the use of commutator. When the armature conductors are under the influence of one pole they carry current in one direction whereas the current is reversed when the conductors are under the influence of other pole. This reversal of current takes place along the magnetic neutral axis. Fig. 1 Note : The reversal of current is likely to take place in short interval when a coil is short circuited by a brush so that transfer of current from one direction to other is carried out without any sparking. This process is called commutation.        Thus a process by which current in the short circuited coil is reversed while it crosses the MNA is called commutation. The time during which the coil remains short circuited is known as...
1 comment
Read more

Demagnetising and Cross Magnetizing Conductors

The conductors which are responsible for producing demagnetizing and distortion effects are shown in the Fig.1. Fig. 1        The brushes are lying along the new position of MNA which is at angle θ  from GNA. The conductors in the region AOC = BOD = 2θ  at the top and bottom of the armature are carrying current in such a direction as to send the flux in armature from right to left. Thus these conductors are in direct opposition to main field and called demagnetizing armature conductors.         The remaining armature conductors which are lying in the region AOD and BOC carry current in such a direction as to send the flux pointing vertically downwards i.e. at right angles to the main field flux. Hence these conductors are called cross magnetizing armature conductors which will cause distortion in main field flux.        These conductors are shown in the Fig. 2 Fig. 2  ...
Post a Comment
Read more

Winding Pitches

Now we will consider the definitions of different types of winding pitches, required in the design of the armature winding. 1.1 Back Pitch         The distance which is measured interns of armature conductors i.e. between top and bottom coil sides of a coil measured around the back of the armature i.e. away from the commutator is called back pitch and is denoted by . It is measured interms of coil sides. Note : Since it is difference between odd and even number, it is always odd number.        The size of the coil is decided by the back pitch. The back pitch is normally equal to coilsides per pole. It is shown for lap and wave type of winding in the Fig. 1. Fig. 1        The back pitch for the winding shown in the Fig. 1 is y b = 14 - 1 = 13 as coilsides 1and 14 are of coil number 1. 1.2 Front Pitch        It is defined as the distance measured between two c...
Post a Comment
Read more