Methods of limiting the effects of armature reaction – The cross-magnetizing effect of armature m.m.f. can be minimised at the design and construction stage of a D.C. machine. Various methods of mitigating the effects of armaturereaction are discussed below :(a) High-reluctance pole tips – If thereluctance of the pole tips is increased, then the magnitudeContinue reading “Methods of Limiting the Effects of Armature Reaction in D.C Machine”
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Armature reaction in D.C Machines
Armature reaction in d.c machines – The armature m.m.f. produces two undesirable effects on the main field flux and these are :(1) net reduction in the main field flux(2) distortion of the main field flux Effects of armature reaction in d.c machine (1) iron losses – These losses depend on the maximum value of fluxContinue reading “Armature reaction in D.C Machines”
D.C Machines
D.C Machines – DC machine is a highly versatile energy conversion device it can meet the demand of loads requiring high starting torque, high accelerating and declerating torques. At the same time DC machine is easily adaptable for drives requiring wide-range speed control and quick reversals. These in herent characteristics can further be modified,if desired,Continue reading “D.C Machines”
Machine Ratings
Machine Ratings – A name-plate fixed to the outside frame of an electrical machine records the data pertaining toits rating. A machine rating species the voltage, current, speed, excitation, pf, efliciency, power output etc. under which it can operate satistactorily. Here satisfactory operation implies that temperature rise of the machine above ambient (or surrounding) temperatureContinue reading “Machine Ratings”
Losses and Efficiency of Electrical Machine
Losses and Efficiency of Electrical Machines – In electrical machines, the power input (mechanical or electrical) is always more than the power output. The difference between power input and power output, under steady state coniditions, Is called power loss in watts. Thus, in accordance with the law of conservation ofpower (or energy), power input =Continue reading “Losses and Efficiency of Electrical Machine”
Pole-Pitch
Pole-Pitch – The peripheral distance between two adjacent poles, is called pole-pitch. Pole-pitch is always expressed in electrical degrees, rather than in mechanical degrees, it can therefore, be inferred that pole pitch is always equal to 180 electrical degrees or π electrical radians.
Synchronous Machines
Synchronous machines In synchronous machines, the armature winding either exports A.C. power (synchro-nous generator) or imports A.C. power (synchronous motor), whereas the field winding is always energised from a D.C. source. In other words, the synchronous machines are doubly excited energy-conversion devices. The generation of e.m.f, in general, depends on the relative motion between fieldContinue reading “Synchronous Machines”
Induction motor has two types of Rotar
Induction motor has two types of Rotar (1) Squirrel cage rotor (2) Wound-rotor ya Slip Ring SQUIRREL CAGE ROTOR – The rotor winding consists of an insulated conductors, in the form of copper or aluminium bars embedded in the semi closed slots. These solids bar short circuited at both ends by end-rings of the sameContinue reading “Induction motor has two types of Rotar”
Transformer Noise
Transformer noise In this case transformers are located in residential area, then the noise emanating from transformers may be annoying to the nearby houses. The hum, leading to noise, originates in the ferromagnetic core of a transformer. The major cause of noise in transformers is the magnetostriction. When ferromagnetic transformer core is magnetized, the coreContinue reading “Transformer Noise”
Pulse Transformer
Pulse Transformer The transformers which handle voltages and currents in the form of pulses are called pulse transformers. The use of such transformers is quite common in radar, television, digital computer and thyristor systems. The functions of pulse transformers are: (1) for changing the amplitude of a voltage pulse, (2) for inverting the polarity ofContinue reading “Pulse Transformer”
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