Electrical Machines

Principle of Induction Motor | Torque Slip Characteristic: Principle of Induction Motor has not been introduced so far. Consider a cylindrical rotor machine with both the stator and rotor wound for three phases and identical number of poles as shown in Fig. 5.40. Assume initially the rotor winding to be open-circuited and let the stator […]

Torque Equation of Synchronous Motor: Figure 5.36 shows a Torque Equation of Synchronous Motor with a round rotor. The rotor is initially stationary with fixed north-south poles created by dc excitation. Let the 3-phase winding of the stator be connected to a 3-phase supply of fixed voltage V (line) and fixed frequency f (this is

Torque in Round Rotor Synchronous Machine: Torque in Round Rotor Synchronous Machine – When the stator and rotor windings of a machine both carry currents, they produce their own magnetic fields along their respective axes which are sinusoidally distributed along the air-gap. Torque results from the tendency of these two fields to align themselves. The

Rotating Magnetic Field: Rotating Magnetic Field – It was seen earlier that the sinusoidal current in any phase of an ac winding produces a pulsating mmf wave in space whose amplitude varies sinusoidally with time. The expression for the fundamental component of this mmf is given in Eq.(5.36). The harmonics of the mmf wave are

Sinusoidally Distributed Current Sheet Concept: It was seen above that a distributed winding gives rise to a stepped mmf wave having a strong fundamental component which will be considered in machine modelling while all the harmonic components will be neglected (justification for the same has been advanced). Now the kind of space distribution of current

MMF of AC Distributed Winding: It has been seen earlier that the armature what-when-how.comof a practical machine has distributed winding wound for the same number of poles as the field winding. As the armature carries current, the resultant field of its current-carrying coils has the same number of poles as the field winding. Our approach

Armature Winding in DC Machine: With reference to the single-coil elementary Armature Winding in DC Machine of Figs 5.13 and 5.14(a) which shows the B-wave of the machine relative to the elementary full-pitched coil, LetConsider that the coil is lying in the interpolar region so that the full flux/pole (Φ) links it positively. Let it

Two layer Winding of Transformer: One important and commonly used way of neatly arranging the end connection of coils in a winding is to place two coil-sides per slot. Each coil then has one coil-side in the bottom half of one slot and the other coil-side in the top half of another slot (one pole

Short Pitch Coil or Chorded Coil: Short Pitch Coil – So far it was assumed that the stator coils are full-pitched (a span of π rad elect). Coils may have a span of less than the full-pitch. This arrangement offers certain advantages. Consider that the coil-span is less than the full-pitch by an elect. angle

Harmonic Analysis in Distributed Winding: The flux density wave of a synchronous machine is never exactly sine wave. Because of odd symmetry of poles (alternately north-south), the space Harmonic Analysis in Distributed Winding of the B-wave comprises odd harmonics only, which induce the corresponding harmonic emf s in the winding. Figure 5.19 shows the fundamental