Electrical Engineering

What are the conditions when the poly phase (here three phase) induction machine will behave as an induction generator? The following are conditions when the induction machine will behave as an induction generator are written below: (a) Slip becomes negative due to this the rotor current and rotor emf attains negative value. (b) The prime mover torque becomes opposite to electric torque. Now let us discuss how we can achieve these conditions. Suppose that an induction machine is coupled with the prime mover whose speed can be controlled. If the speed of the prime mover is increased such that the slip becomes negative (i.e. speed of the prime mover becomes greater than the synchronous speed).Due to this, all the conditions that we have mentioned above will become fulfilled and machine will behave like an induction generator. Now if the speed of the prime mover is further increased such that it exceeds the negative maximum value of the torque produced then the generati...

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: E f which denotes excitation voltage V t which denotes terminal voltage I a which denotes the armature current θ which denotes the phase angle between V t and I a ᴪ which denotes the angle between the E f and I a δ which denotes the angle between the E f and V t r a which denotes the armature per phase resistance In order to draw the phasor diagram we will use V t 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 E f . (2) Phasor E f is always ahead of V t . These two points are necessary for making the...

In modern power systems isolated generators are veryrare. Power systems are highly interconnected and many generators share the load. The first problem of an engineer is connectinga synchronous generator onan existingbus.   CONNECTING a GENERATOR to a BUS The above figure  illustrates a generator G1 which is already connected to a power grid under load. Generator 2 has to be connected or “brought on line” 1.  The prime mover of the generator has to bringthe speed of the shaft close to the rated speed of the generator. 2.  The excitation of the generator has to be increasedto give a no-load output voltage as close as possible to the existingbus voltage We want to create a phasor rotation for generator 2 output similar to the bus voltage phasor. 3.  Observe the lights which are connected across the switches: theyshould beat, first get brighter and then dimas the phasors for generator and bus respectivelyshift. If the 3 lights beat concurrently...