The circuit model of a cylindrical rotor synchronous generator or alternator is shown in Figure-1.Let, 𝑉 = Terminal voltage per phase$𝐸_{𝑓}$ = Excitation voltage per phase$𝐼_{𝑎}$ = Armature current$\delta$ = Load angle (between 𝑉 and $𝐸_{𝑓}$ )By applying KVL in the circuit, we get, $$\mathrm{𝑬_{𝒇} = 𝑽 + 𝑰_{𝒂}𝒁_{𝒔} … ... Read More

The circuit model of a cylindrical rotor synchronous generator is shown in Figure-1.Let, 𝑉 = Terminal voltage per phase$𝐸_{𝑓}$ = Excitation voltage per phase$𝐼_{𝑎}$ = Armature current$\delta$ = Load angle or angle between 𝑉 and $𝐸_{𝑓}$Also, the phasor diagram of the alternator at lagging power factor is shown in Figure-2.For ... Read More

The Potier Triangle Method is used in determining the voltage regulation of alternators. It is also known as the Zero Power Factor (ZPF) method. The following assumptions are made in the Potier triangle method −The armature reaction MMF is constant.The open-circuit characteristic (O.C.C.) taken on no-load accurately represents the relation ... Read More

In practice, a very large number of 3-phase alternators operate in parallel because the various power stations are interconnected through the national grid. The electric power systems are interconnected for economy and reliable operation. This interconnection of power systems requires alternators to operate in parallel with each other.In a generating ... Read More

Consider two synchronous generators or alternators are operating in parallel and their load-frequency characteristics are shown in the figure.Let$𝑓_{1(𝑛𝑙)}$ = No load frequency of alternator 1$𝑓_{2(𝑛𝑙)}$ = No load frequency of alternator 2$𝑓_{1(𝑓𝑙)}$ = Full load frequency of alternator 1$𝑓_{2(𝑓𝑙)}$ = Full load frequency of alternator 2𝑓 = Common operating ... Read More

The slip test is a simple no-load test, which is used to determine the direct-axis and quadrature-axis synchronous reactances of a salient-pole synchronous machine. In this test, a small voltage at rated frequency is applied to the 3-phase stator winding of the synchronous machine. The field winding is unexcited and ... Read More

A synchronous machine may be subjected to various disturbances. Any cause of disturbance will produce electrical and mechanical transients. These transients may result from switching, from sudden changes of load, from sudden short-circuits between line and ground or between double lines or between all the three lines. These disturbances produce ... Read More

Magnetic Axes of RotorThe figure shows the direct axis and the quadrature axis of a rotor −Direct AxisThe axis of symmetry of the magnetic poles of the rotor is called as direct axis or d-axis. The axis of symmetry of the north magnetic poles of the rotor is known as ... Read More

A synchronous machine under steady running conditions has a driving torque at every instant balancing its retarding torque. The retarding torque is developed by phase displacement ($\delta$) between the axis of the stator and rotor poles. A mechanical rotary system possesses inertia and restoring torque that tends to restore its ... Read More

In the ampere-turn method (which is also known as the MMF method), the effect of armature leakage reactance is replaced by an equivalent additional armature reaction MMF so that this MMF can be combined with the armature reaction MMF.In order to predict the voltage regulation of the alternator by the ... Read More