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Eddy current damping is not practical in moving iron instruments because these instruments rely on a magnetic field produced by a coil to move a ferromagnetic element. The rapid motion of this element can create eddy currents in nearby conductive materials, but the inherent design and operation of moving iron mechanisms do not allow for effective energy dissipation through these currents. Additionally, the presence of eddy currents can interfere with the magnetic field and the accuracy of the instrument, leading to potential measurement errors. Thus, other damping methods, such as air damping, are preferred.
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Why are moving iron test instruments not used with DC although they can work in DC?
For moving-iron instrument magnetic field is caused when the current (voltage) passes the fixed circle. When the current (voltage) passes the fixed circle，the two iron plates are magnetized ,rotational torque is resulted, the deflection angle indicate measured current. Because the magnetized polarity is same for AC or DC, moving-iron instrument can be used in AC and DC circuit. For permanent-magnet moving-coil instrument magnetic field is caused by the permanent-magnet, When the DC current passes the moving coil, rotational torque is resulted,so the deflection angle indicate measured DC current. As AC current passes the moving coil ,because inertia of moving parts of meter the deflection angle indicate rotational torque average, but rotational torque average is zero in cycle, moving parts of meter is´t deflec,so permanent-magnet moving-coil instrument only is used in DC circuit.
Can instrument transformers be used to extend the range of a moving coil voltmeter?
Not directly, as MC instruments are direct-current instruments, whereas instrument transformers only work on a.c.
Why moving iron is used in both AC and DC current?
A moving iron instrument works by means of a coil that attracts a moving iron mass that is attached to a pivoted pointer which moves across a graduated scale. The iron mass will be attracted towards the coil, regardless of the magnetic polarity of the coil. So, as an AC current continually reverses the magnetic polarity of the coil, the iron mass is always attracted towards the coil, never repelled by it. Similarly, a moving iron instrument doesn't care in which direction a DC current is flowing. So the instrument works equally well with both AC and DC currents. Moving iron instruments, however, are not as accurate as moving coil instruments which, of course, are sensitive to the direction of current.
What is the technique used for damping torque?
Damping torque is typically achieved through the use of viscous damping or frictional damping mechanisms. Viscous damping involves the use of a fluid, such as oil, to create resistance against the motion of a moving part, thereby dissipating energy and reducing oscillations. Frictional damping relies on the contact between surfaces to generate resistance, which also serves to dampen motion. Both techniques are commonly employed in various mechanical systems to enhance stability and control.
Is Voltmeter is a moving iron Instrument or moving coil instrument?
If this is a homework related question, you really should consider trying to solve it yourself before looking at this answer. Otherwise, the value of the lesson, and the reinforcement provided by the assignment, will be lost to you.A moving coil measuring instrument has a coil attached to the indicator, surrounded by a magnet.A moving iron measuring instrument has a magnet attached to the indicator, surrounded by a coil.In both cases, the indicator is driven by magnetic torque caused by current flow in the coil.
Why eddy current damping is not used in moving iron instruments?
because eddy current is produced by the heat produced in winding
How many types of damping torque in moving instruments?
air friction ,fluid friction, eddy current
What are the different methods of damping used in analog indicating instruments?
Damping torque can be provided by: (a) air friction damping (b) fluid friction damping (c) eddy current damping. In air friction damping, a light piston moves with a very small clearance in air chamber. The piston moves against pressure of air in air chamber. In fluid friction damping, light varies are attached to spindle of moving system. The movement of spindle is suppressed due to fluid friction, Eddy current damping is one of the most efficient method of damping. It is based on the principle that whenever a sheet of conducting but non magnetic material like copper or aluminum moves in magnetic field, eddy currents are induced.
Why are moving iron instruments unpolarized?
Moving-coil instruments are polarised, not unpolarised. This is because they are direct current instruments, and the direction of the current determines the direction in which the instrument's point will move. If a moving coil instrument is connected incorrectly, then the instrument will try and read 'downscale' -in other words, the resulting torque will try and move the pointer backwards.AnswerA moving-iron meter operates by the repulsion between a fixed iron pole piece, and a moving iron pole piece to which the pointer is attached. The magnetic polarity of the fixed and moving pole pieces is determined by the direction of current flowing though a coil. The magnetic polarities induced into the fixed and moving iron pole pieces, when the current flows in one direction, are both north; and, when the current flows in the oppositedirection are both south. So the pole pieces always repel each other, regardless of current direction.
Is it possible to obtain current from air in moving bus?
Nope.
Why are moving iron test instruments not used with DC although they can work in DC?
For moving-iron instrument magnetic field is caused when the current (voltage) passes the fixed circle. When the current (voltage) passes the fixed circle，the two iron plates are magnetized ,rotational torque is resulted, the deflection angle indicate measured current. Because the magnetized polarity is same for AC or DC, moving-iron instrument can be used in AC and DC circuit. For permanent-magnet moving-coil instrument magnetic field is caused by the permanent-magnet, When the DC current passes the moving coil, rotational torque is resulted,so the deflection angle indicate measured DC current. As AC current passes the moving coil ,because inertia of moving parts of meter the deflection angle indicate rotational torque average, but rotational torque average is zero in cycle, moving parts of meter is´t deflec,so permanent-magnet moving-coil instrument only is used in DC circuit.
Is EM Damping fields real?
Electromagnetic damping fields are a theoretical concept used in physics to describe the effects of electromagnetic fields on moving charged particles. While the idea of EM damping fields is used in theoretical models, their direct observation is not yet possible due to the complex nature of electromagnetic interactions at small scales.
What are the functions of moving coil instrument?
The function of the moving coil is to deflect the instruments needle across a calibrated scale to give the meter operator an accurate reading of what ever he is testing. The moving coil is given a minute current, through internal instrument circuity, a sample of the potential that is being measured.
Can instrument transformers be used to extend the range of a moving coil voltmeter?
Not directly, as MC instruments are direct-current instruments, whereas instrument transformers only work on a.c.
Why moving iron is used in both AC and DC current?
A moving iron instrument works by means of a coil that attracts a moving iron mass that is attached to a pivoted pointer which moves across a graduated scale. The iron mass will be attracted towards the coil, regardless of the magnetic polarity of the coil. So, as an AC current continually reverses the magnetic polarity of the coil, the iron mass is always attracted towards the coil, never repelled by it. Similarly, a moving iron instrument doesn't care in which direction a DC current is flowing. So the instrument works equally well with both AC and DC currents. Moving iron instruments, however, are not as accurate as moving coil instruments which, of course, are sensitive to the direction of current.
What are the advantages of moving coil instrument?
Advantages are:- high sensitivity, uniform scale, very effective and reliable eddy current danping well shelded from any stray magnetic field. Disadvantages are:- very expensive, only suitable for direct current and voltages.
What is the technique used for damping torque?
Damping torque is typically achieved through the use of viscous damping or frictional damping mechanisms. Viscous damping involves the use of a fluid, such as oil, to create resistance against the motion of a moving part, thereby dissipating energy and reducing oscillations. Frictional damping relies on the contact between surfaces to generate resistance, which also serves to dampen motion. Both techniques are commonly employed in various mechanical systems to enhance stability and control.
