Category: Rotating Machines

Electric Motor Characteristics

Electric Motor Characteristics: The machine and the load are the two components of an electro-mechanical energy-conversion system, and the Electric Motor Characteristics, generally, play a predominant part in the operating behavior of the complete system. In choosing an electric motor its speed-torque characteristic is needed to be known to a fair degree of accuracy and […]

Rating and Loss Dissipation

Rating and Loss Dissipation: The Rating and Loss Dissipation of a synchronous generator is its operating voltage, frequency, speed and kVA/MVA output at a specified power factor. In case of motors the output rating is given in kW (older practice was to specify the rated output in horse-power (1 hp = 746 W)). The dc […]

Rotating Electrical Machines Losses and Efficiency

Rotating Electrical Machines Losses and Efficiency Classification: Rotating Machines Losses Classification – The Losses and Efficiency of a transformer have been studied in earlier lesson. As in the case of transformers, it is more accurate to determine the Rotating Electrical Machines Losses and Efficiency rather than by the direct load test in which the input […]

Magnetic Flux Leakage in Rotating Machines

Magnetic Flux Leakage in Rotating Machines: The Magnetic Flux Leakage in rotating machines is that flux which links only the stator or only the rotor windings. Because of the presence of air-gap in the magnetic circuit of machines, the leakage in these is quite significant and cannot be neglected in analysis as could be done […]

Principle of Induction Machine

Principle of Induction Machine: Principle of Induction Machine 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 be connected to an […]

Synchronous Machine Torque Equation

Synchronous Machine Torque Equation: Figure 5.36 shows a Synchronous Machine Torque Equation 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 known as […]

Torque in Round Rotor Machine

Torque in Round Rotor Machine: Torque in Round Rotor 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 flux components […]

Rotating Magnetic Field

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 […]

Current sheet Concept

Current sheet Concept: 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 […]

MMF of AC Distributed Winding

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 […]