The voltage regulation of an alternator or synchronous generator is defined as the rise in the terminal voltage when the load is decreased from full-load rated value to zero. The speed and field current of the alternator remain constant.In other words, the voltage regulation of the alternator can be defined ... Read More

Armature Leakage ReactanceIn an AC electrical machine, the magnetic flux set up by the load current which does not contribute to the useful magnetic flux of the machine is known as leakage flux. This leakage flux sets up a self-induced EMF in the armature winding of the machine. The leakage ... Read More

Consider a 2-pole alternator as shown in Figure-1. Suppose that the alternator is loaded with an inductive load of zero power factor leading.. Thus, the phase currents 𝐼𝑅 , 𝐼𝑌 and 𝐼𝐵 will be leading their respective phase voltages 𝐸𝑅 , 𝐸𝑌 and 𝐸𝐵 by 90°. Figure-2 shows the phase ... Read More

Consider a 2-pole alternator as shown in Figure-1. Suppose that the alternator is loaded with an inductive load of zero power factor lagging. In this case, the phase current 𝐼𝑅 , 𝐼𝑌 and 𝐼𝐵 will be lagging with their respective phase voltages 𝐸𝑅 , 𝐸𝑌 and 𝐸𝐵 by 90°. The ... Read More

Practically, most of the synchronous generators or alternators have stationary armature and rotating field.A stationary armature-rotating field alternator has several advantages over a rotating armature type alternator, as given below −When a stationary armature is used in the alternator, the output current can be taken directly from the fixed terminals ... Read More

The synchronous impedance method or EMF method is used to determine the voltage regulation of the larger alternators. The synchronous impedance method is based on the concept of replacing the effect of armature reaction by an imaginary reactance.For an alternator, $$\mathrm{𝑽 = 𝑬_{𝒂} − 𝑰_{𝒂}𝒁_{𝒔} = 𝑬_{𝒂} − 𝑰_{𝒂}(𝑅_{𝒂} + ... Read More

Unsaturated Synchronous ReactanceAt low excitations, the open-circuit characteristic (OCC) of an alternator coincides with the air-gap line, thus, the synchronous impedance of the alternator is constant and this value of the synchronous impedance is known as linear or unsaturated synchronous impedance.The unsaturated synchronous reactance (denoted by Xsu) can be obtained ... Read More

In an alternator or synchronous generator, the actual generated voltage consists of the summation of two component voltages. One of these component voltages is the excitation voltage  (𝐸exc); it is the voltage that would be generated because of the field excitation only. The excitation voltage is the voltage that would ... Read More

In a synchronous machine, the short-circuit ratio (SCR) is an important factor. The SCR affects the physical size, operating characteristics and cost of the synchronous machine.Low Value of SCRWith a low value of SCR, the synchronous machine is very sensitive to the load variations, i.e., the alternator has a large ... Read More

What is Hunting in Alternator?When an alternator or synchronous generator is running under normal condition, the armature field and the rotor magnetic field will be rotating in the same direction at synchronous speed.When either a sudden change in the load of the alternator or a change in the torque of ... Read More