Metadyne is a cross-field machine. The cross-field machines are special DC machines having an additional set of brushes on the direct-axis or d-axis. This arrangement of brushes enables the use of armature MMF to provide most of the excitation and achieve high power gains.Construction and Working of MetadyneAn ordinary DC ... Read More

The synchronising torque coefficient is defined as the torque at which the synchronous speed gives the synchronising power. If represents the synchronising torque coefficient, then$$\mathrm{𝜏_{𝑠𝑦𝑛} =\frac{1}{𝜔_{𝑠}}𝑚\frac{𝑑𝑃}{𝑑𝛿}\:Nm/electrical\:radian …(1)}$$Also, $$\mathrm{𝜏_{𝑠𝑦𝑛} =\left (\frac{1}{𝜔_{𝑠}}𝑚\frac{𝑑𝑃}{𝑑𝛿} \right)\cdot \frac{𝜋𝑝}{180°}\:Nm/mechanical \:degree …(2)}$$Where, m is the number of phase of the machine, 𝜔𝑠 = 2𝜋𝑛𝑠 is the angular synchronous ... Read More

What is an Infinite Bus?Normally, in a power system, more than one synchronous generators or alternators operate in parallel. The alternators may be located at different places.A group of alternators located at a single place may be treated as a single large alternator.Also, the alternators connected to the same busbar ... Read More

The zero power factor characteristics (ZPFC) is the graph plotted between the armature terminal voltage per phase and the field current, when the machine being operating with constant rated armature current at synchronous speed and zero lagging power factor. The ZPFC is also known as Potier Characteristics after its originator.In ... Read More

When the flux density distribution in the alternator is non-sinusoidal, the induced voltage in the winding will also be non-sinusoidal. Thus, the pitch factor or coil span factor, distribution factor and winding factor will be different for each harmonic voltage.Pitch Factor for nth HarmonicAs the electrical angle is directly proportional ... Read More

When a synchronous machine is synchronised to infinite busbars, it has an inherent tendency to remain in synchronism.Rotor is accelerated – Consider an alternator delivering a steady power P at a steady load angle δ. Suppose, due to some transient disturbance, the rotor is accelerated so that the load angle ... Read More

Short Circuit RatioThe ratio of the field current required to generate rated voltage on open-circuit to the field current required to circulate rated armature current on short circuit is called as the short-circuit ratio (SCR) of a synchronous machine.Calculation of SCRThe short circuit ratio of a synchronous machine can be ... Read More

The frequency of the generated voltage by the alternator depends upon the number of field poles and the speed at which the field poles are rotated. One complete cycle of the voltage being generated in an armature coil when a pair of field poles i.e. one north pole and one ... Read More

Coil span or coil pitch is defined as the distance between the two sides of a coil.Pole pitch is defined as the angular distance between the central line of one pole to the central line of the next pole. A pole pitch is always 180° electrical regardless of the number ... Read More

For a salient-pole synchronous generator or alternator, the per phase reactive power is given by, $$\mathrm{𝑄_{1𝜑} =\frac{𝑉𝐸_{𝑓}}{𝑋_{𝑑}}cos\:𝛿 −\frac{𝑉^{2}}{2𝑋_{𝑑}𝑋_{𝑞}}\lbrace{(𝑋_{𝑑} + 𝑋_{𝑞} ) − (𝑋_{𝑑} − 𝑋_{𝑞})\:cos\:2\delta}\rbrace … (1)}$$Where, V is the terminal voltage per phase.Ef is the excitation voltage per phase.$\delta$ is the per phase angle between Ef and V.Xd is ... Read More