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In the conventional dc machine (with a closed continuous commutator winding on its armature), for example, full-wave rectification of the alternating voltage induced in individual armature coils is achieved by means of a commutator, which makes a unidirectional voltage available to the external circuit through the stationary carbon brushes held against the commutator surface.The armaturewindings of dcmachines are located on the rotor because of this necessity for commutation and are of the closed continuous type, known as lap and wavewindings. The simplex lap winding has as many parallel paths as there are poles, whereas the simplex wave winding always has two parallel paths. The winding connected to the commutator, called the commutator winding, can be viewed as a pseudostationary winding because it produces a stationary flux when carrying a direct current, as a stationarywindingwould. The direction of the flux axis is determined by the position of the brushes. In a conventional dc machine, in fact, the flux axis corresponds to the brush axis (the line joining the two brushes). The brushes are located so that commutation (i.e., reversal of current in the commutated coil) occurs when the coil sides are in the neutral zone, midway between the field poles. The axis of the armature mmf is then in the quadrature axis, whereas the stator mmf acts in the field (or direct) axis. Figure shows schematic representations of a dc machine. The commutator is thus a device for changing the connections between a rotating closed winding and an external circuit at the instants when the individual coil-generated voltages reverse. In a dc machine, then, this arrangement enables a constant and unidirectional output voltage. The armature mmf axis is fixed in space because of the switching action of the commutator (even though the closed armature winding on the rotor is rotating), so the commutator winding becomes pseudostationary.
The following four output displays of an oscilloscope (right hand side, below) show waveforms of a biased diode ac circuit. An example is illustrated on the left hand side. VIN is
Q. A 100-kVA, 2300:230-V, 60-Hz, single-phase transformer has the following parameters: R 1 = 0.30 , R 2 = 0.003 , RC 1 = 4.5k, X 1 = 0.65 , X 2 = 0.0065 , and Xm 1 = 1.
Hybrid parameters (or) h - parameters:- If the input current that is denoted as i 1 and output Voltage that is denoted as V 2 are takes as independent variables, input v
Q. Illustrate Hexadecimal Number System? A big difficulty with the binary system is verbosity. To symbolize the value 202 requires eight binary digits. The decimal version n
1. The circuit below will be most efficiently analyzed by obtaining the Thevenin equivalent circuit for the circuit to the left of the points (a-b) on the schematic. The capacitor
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Write a brief note on MMX technology. MMX (Multimedia extensions) technology adds 57 new types of instructions to the Pentium - 4 microprocessors instruction set. The MMX tech
Calculate the diameter of copper wire of length 100 metres used as winding material in a transformer such that the resistance of the whole winding is 2 ohms. Calculate the diameter
Explain the Synchronous Up-Down Counters? The circuit of a 3-bit synchronous up-down counter and a table of its sequence are shown below. Alike to an asynchronous up-down count
I WANT TO KNOW WHAT IS THE THORY OF PLOTTING V-I CHARACTERISTIC CURVE OF SILICON DIODE ???
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