Electrical Engineering ⇒ Topic : Moving-Iron (M.I.) Ammeters and Voltmeters
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DJ
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Moving-Iron (M.I.) Ammeters and Voltmeters This type of instrument is principally used for the measurement of alternating currents and voltages, though it can also be used for d.c. measurements. There are two types of moving-iron instruments. (1) Attraction type in which a single soft-iron vane (or moving iron) is mounted on the spindle and is attracted towards the coil when operating current flows through it. (2) Repulsion type in which two soft-iron vanes are used; one fixed and attached to the stationary coil while the other is movable (i. e. moving iron) and mounted on the spindle of the instrument. When operating current flows through the coil, the two vanes are magnetised, developing similar polarity at the same ends. Consequently, repulsion takes place between the vanes and the movable vane causes the pointer to move over the scale. In case the instrument is to be used as an ammeter, the coil has a fewer turns of thick wire so that the ammeter has low resistance a desirable requirement. In case it is to be used as a voltmeter, the coil has a large number of turns of fine wire so that the voltmeter has high resistance a desirable requirement | |
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DJ
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Moving-Iron (M.I.) Ammeters and Voltmeters This type of instrument is principally used for the measurement of alternating currents and voltages, though it can also be used for d.c. measurements. There are two types of moving-iron instruments. (1) Attraction type in which a single soft-iron vane (or moving iron) is mounted on the spindle and is attracted towards the coil when operating current flows through it. (2) Repulsion type in which two soft-iron vanes are used; one fixed and attached to the stationary coil while the other is movable (i. e. moving iron) and mounted on the spindle of the instrument. When operating current flows through the coil, the two vanes are magnetised, developing similar polarity at the same ends. Consequently, repulsion takes place between the vanes and the movable vane causes the pointer to move over the scale. In case the instrument is to be used as an ammeter, the coil has a fewer turns of thick wire so that the ammeter has low resistance a desirable requirement. In case it is to be used as a voltmeter, the coil has a large number of turns of fine wire so that the voltmeter has high resistance a desirable requirement | |
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