Two Reaction Theory – Salient Pole Synchronous Machine

Two Reaction Theory was proposed by Andre Blondel. The theory proposes to resolve the given armature MMFs into two mutually perpendicular components, with one located along the axis of the rotor of the salient pole. It is known as the direct axis or d axis component. The other component is located perpendicular to the axis…

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Armature Reaction in a Synchronous Machine

The effect of Armature (stator) flux on the flux produced by the rotor field poles is called Armature Reaction. When the current flows through the armature winding of the an alternator, a flux is produced by the resulting MMF. This armature flux reacts with the main pole flux, causing the resultant flux to become either…

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Effect of Load on a Synchronous Motor

A synchronous motor runs at constant synchronous speed, regardless of the load. Let us see the effect of the load change on the motor. Consider a synchronous motor operating initially with a leading power factor. The phasor diagram for leading power factor is shown below. The load on the shaft is increased.the rotor slows down…

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Short Circuit Ratio of a Synchronous Machine

The Short Circuit Ratio (SCR) of a synchronous machine is defined as the ratio of the field current required to generate rated voltage on an open circuit to the field current required to circulate rated armature current on short circuit. The short circuit ratio can be calculated from the open circuit characteristic ( O.C.C) at…

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Generator Synchronization

A stationary generator must not be connected to live Busbars because the induced EMF is zero at standstill resulting in a short circuit. The Synchronisation procedure and the equipment for checking it are the same whether one alternator is to be connected in parallel with another alternator, or an alternator is to be connected to…

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Capability Curve of a Synchronous Generator

The Capability Curve of a Synchronous Generator defines a boundary within which the machine can operate safely. It is also known as Operating Charts or Capability Charts. The permissible region of operation is restricted to the following points given below. The MVA loading should not exceed the generator rating. This limit is determined by the…

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Hunting in a Synchronous Motor

The phenomenon of oscillation of the rotor about its final equilibrium position is called Hunting. On the sudden application of load, the rotor search for its new equilibrium position and this process is known as Hunting. The Hunting process occurs in a synchronous motor as well as in synchronous generators if an abrupt change in…

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V Curve of a Synchronous Motor

V curve is a plot of the stator current versus field current for different constant loads. The Graph plotted between the armature current Ia and field current If at no load the curve is obtained known as V Curve. Since the shape of these curves is similar to the letter “V”, thus they are called…

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Synchronizing Power and Torque Coefficient

Definition: – Synchronizing Power is defined as the varying of the synchronous power P on varying in the load angle δ. It is also called Stiffness of Coupling, Stability or Rigidity factor. It is represented as Psyn.A synchronous machine, whether a generator or a motor, when synchronised to infinite Busbars has an inherent tendency to…

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Starting of a Synchronous Motor

Starting of the Synchronous Motor does not take place on its own. This means that the Synchronous Motor is not Self Starting. It can be started by the following methods given below. Starting with the help of an External Prime Mover Starting with the help of Damper Windings The detailed description of the methods is…

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