Megger

The megger is an instrument used for the measurement of high resistance and separation resistance, Essentially the Magger insulation tester consists of a hand-driven d.c. generator and a direct reading true ohmmeter. A simplified transcend of electrical connections of the instrument is shown in fig. 6.242 Permanent magnets provide the dramatics for both the generator & the ohm-meter. The moving element of the ohm-meter consist of trio waves known as real (or deflecting) whirl, jam (or apply) coil and compensating coil, which argon mounted rigidly to a pivoted central shaft and which argon free to rotate over a stationary C-shaped manoeuvre core. The coils are connected to the circuit by means of rubber band leads (or ligaments) that exert no restoring torque on the moving element. and so the moving element may take up whatever position over the scale when the generator handle is stationary. The menstruation (or deflection) coil is connected in series wi th the resistance R between one generator last-place and the test closing marked L. The series resistance R protects the current (or deflecting) coil in case the test terminals are short-circuited and also go over the range of the instrument.

The crush (or control) coil in series with a compensating coil and protection resistance R is connected crosswise the generator terminals. Compensating coil is provided to obtain better scale proportions and to advert the instrument a static. When the current from the generator flows finished pressure coil, the coil tends to set itself at right angles to the field of the morose magnet. With the test terminals open, corresponding to infi nite resistance, no current flows with defl! ecting coil. The pressure coil thus governs the motion of the moving element, key it to move to its extreme counter-clockwise position. The point on the scale indicated by the pointer under this condition is marked infinite resistance. licensed coil is wound to produce clockwise torque on the...If you want to get a full essay, order it on our website: OrderEssay.net

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