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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.
Mechanical Structure of Depletion Type MOSFET The mechanical structure of this type of device is displayed in figure. In an IC, we would locate two n-type regions side by side
Induction motors are often braked rapidly by a technique known as plugging, which is the reversal of the phase sequence of the voltage supplying the motor. Assume that a motor with
A symmetrical fluctuating message, with |f(t)| max = 6.3 V and KCR = 3, is to be encoded by using an encoder that employs an 8-bit natural binary code to encode 256 voltage levels
Q. What do you mean by Pinch off voltage? As the voltage Vds is increased from 0 to a few volts, the drain current will increase as determined by Ohm's law and the plot of Id
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Q. Explain Read-only memory? ROM is nonvolatile (because it maintains its contents even when its power is shut off) and is used to store data and programs that do not change du
Q. Prove mathematically that the operating point does not depend on beta, in a potential divider bias circuit ? To determine the operating point, consider the input section of
Q. For the electromagnet shown in Figure, the λ-i relationship for the normalworking range is given by i = aλ 2 + bλ(x -d) 2 ,where a and b are constants. Determine the force app
Write discussion on Construction and working of analog type storage oscilloscope
Q. Show that the image frequency for an FM station does not fall in the range of 88.1-107.9 MHz, regardless of the choice of high- or low-side local oscillator.
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