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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.
What are the modes used in display modes? 1. Left Entry mode In the left entry mode, the data is going into from the left side of the display unit. 2. Right Entry Mode
Q. The magnetization curve taken at 1000 r/min on a 200-V dc series motor has the following data: Field current, A: 5 10 15 20 25 30 Voltage, A: 80 160 202 222 236 244 Th
What do you mean by external data bus? External Data Bus: A bus which connects a computer to the peripheral devices. The microprocessor-8088 has 16-bit registers, 20-bit add
An ice plant produces 12tonn of ice per day at 0 0 C using water at 300C. The plant operates on reversed Carnot cycle between -15 0 C and 28 0 C. If the actual C.O.P. is 50% of the
Q. Counters are used to realize various dividers in the schematic representation of the digital clock shown in Figure. The blocks labeled "logic array" are logic gate combinations
Followings are the Disadvantages of PLC a.Too much work required in connecting wires. b.Difficulty with changes or replacements. c.Difficulty in finding errors requi
Explain Inverse Discrete-Time Fourier Transform 1. Observe the same things among this formula and the inverse analogue Fourier transform: The (1/2π) factor The sign
Why dummy coils are used in generators
Connect the 2 kHz (sin ωt) signal to input A of the "Adder" module Connect input B to ground (GND). Connect the outputof the"Adder"(GA+gB) to input A-CH1 of "Scope Selector".
What is dummy coil?
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