UJT Relaxation Oscillator is a nonlinear oscillator which generates a non-sinusoidal signal such as sawtooth waveforms as output.
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An N-channel JFET is fabricated (or constructed) on N-type semiconductor bar that is as shown in figure (1). The left end of the N-type semiconductor bar is known as source and the right end is known as drain. Construction of N-channel JFET To design a N-channel JFET, the N-type bar is heavily doped with two
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A current transformer (CT) is nothing but a coil wound on a toroidal core. When a large current carried by a conductor is to be measured, it is advisable to avoid the direct connection of ammeter in this high current circuit. For this purpose a current transformer is used. Fig. 1 : Connection of Current
The three phase autotransformer is a combination of three single phase autotransformers. It has three windings, one per phase. Fig. 1 : 3 Phase Autotransformer.
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Swinburne’s test is the simplest indirect method to determine the efficiency of D.C machine. In this test the no- load losses are measured separately and from their knowledge, efficiency at any desired load can be predetermined in advance. Figure 1: Arrangement of Swinburne’s test.
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Retardation Test is used for finding the efficiency of shunt wound DC machines. In this test, the rotational losses or stray losses are measured and from their knowledge efficiency at any desired load can be determined. Figure 1: Arrangement of Retardation Test.
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Figure 1: Arrangement of Brake Test. Brake test is a direct testing method used to find the efficiency of a DC motor. The arrangement for performing brake test on a DC motor is shown in figure (1).
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Earth Tester generally used for measurement of earth resistance. Figure 1: Earth Tester.
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The different methods of speed control of DC shunt motor are, Armature control method Field control method Ward-Leonard method. Armature Control Method
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A four point starter is a protective device used in shunt and compound DC motors to limit the high starting current in the absence of back e.m.f. The construction of four point starter is similar to three point starter except the connection of NVC (No-volt coil).
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