These instruments use soft iron which is a ferromagnetic material. This effect is utilised in repulsion type moving iron instruments. Classification of moving iron instruments a media to. Sep 05, 2012 moving iron instruments there are of two types of moving iron instruments. Force between a current carrying coil and a permanent magnet. The figure shows an attractiontype moving iron mi instrument. When the coil is excited it produces magnetic field. It produces an imaginary bar magnet when carrying current. Repulsion or double iron type figure 1 attraction or singleiron type figure 2 the brief description of different components of a movingiron instrument is given below. There are two general types of moving iron instruments namely. Difference between moving coil instrument,moving iron. Thus moving iron instruments are unpolarised instruments i. Construction of attraction type moving iron instruments the simplest form of attraction type moving iron instrument uses a solenoid and a moving oval shaped soft iron pivoted eccentrically. The instrument can be constructed to measure current and voltage to an accuracy needed in most engineering works and still be cheaper as compared any other type of a.
Classification of moving iron instruments moving iron instruments are of two types i attraction type. The iron van is so situated that it can move in the magnetic field produced by a stationary coil. The angular deflection of needle of moving iron instruments is related to the current flowing through the field coil. Difference between moving coil instrument,moving iron instrument. Which of the following instruments can be used for full scale deflection of 300o. Movingiron ammeters and voltmeters there are two basic forms of these instruments i. The basic working principle of these instruments is very simple that a soft iron piece if brought near magnet gets attracted by the magnet. Due to this square law response, the moving iron instrument scale is nonuniform.
Moving iron instruments principle, operation and type. The current to be measured is passed through the coil, coil produced the magnetic field. A sectional view of the attraction type moving iron instrument is shown. Moving iron instrument this instrument is one of the most primitive forms of measuring and relay instrument. This principle is used in moving iron attraction type instrument. For low voltage range the power consumption is higher. There are two general types of movingiron instruments namely. A hollow circular coil is used and one of the iron pieces is attached inside the hollow coil. A soft iron vane iv is attached to the moving system. The operation of a permanentmagnet movingcoil type instrument is be based upon the principle that when a currentcarrying conductor is placed in a magnetic field, it is acted upon by a force that tends to move it to one side and out of the field. Moving iron instrument type iqe type iqe 72 iqe 96 front flange mm 72 x 72 96 x 96 housing mm 66 x 66 89 x 89 class 1.
A permanent magnet moving coil pmmc meter also known as a darsonval meter or galvanometer is an instrument that allows you to measure the current through a coil by observing the coils angular deflection in a uniform magnetic field. It is a permanent magnet moving coil instrument plus a rectifier is also suitable for acdc measurements. In both the attraction and repulsion type movingiron instruments it is found that for a given position of the moving system, the value of the deflecting torque is proportional to the square of the current, so long as the iron is working below saturation. Before this article, i have shared an electrical measuring instrument covering all different instruments and their uses the main functions of the measuring instrument are indicating, recording, detecting, controlling and testing the electrical units. This is the second article based on the electrical instruments classification of electrical measuring instruments. A moving iron piece is attracted towards the coil due to magnetic. Moving iron instruments attraction type easiest explained. When the current to be measured is passed through the coil c, a magnetic field is produced. To produce the magnetic field due to current flowing through it and also to magnetize the. Due to magnetic field the moving iron moves from the weaker field outside the. Deflection torque is proportional to the square of the current. The instrument in which the moving iron is used for measuring the flow of current. This field attracts the eccentrically mounted vane on the spindle towards it. It is clear that whatever may be the direction of the current in the coil of the instrument, the iron vanes are so magnetized that there is always a force of attraction in the attraction type and repulsion in the repulsion type of instruments.
Repulsion or double iron type figure 1 attraction or single iron type figure 2 the brief description of different components of a moving iron instrument is given below. When current flows in the solenoid, a pivoted softiron disc is attracted towards the solenoid and the movement causes a pointer to move across a scale. Attraction type the instrument in which the iron plate attracts from the weaker field towards the stronger field such type of instrument is known as the attraction type instrument. Another type of instrument that is usually classed with the attractive types of instrument is shown in fig. On passing current through the coil produces magnetic field which attracts soft. The force of this attraction depends upon the strength said magnetic. Classification of moving iron instrument moving iron instrument are of two types attraction type repulsion type 4. The deflection of needle of moving iron instrument is given in terms of rms value of voltage or current. The magnetic field is obtained by a multiturn rectangular shaped coil. Advantages and disadvantages of movingiron instruments. Repulsionattraction type current responsive instrument. Moving iron instruments there are of two types of moving iron instruments. Attraction type construction of the attraction type moving iron instrument is as shown in the given figure. Moving iron instruments attraction and repulsion type.
Suitable for low frequency and high power circuits. It consists of a fixed cylindrical hollow coil which carries the operating current. In attraction type moving iron instruments, an ovalshaped disc made up of soft iron is pivoted on the spindle near the coil. As the angular deflection of moving iron instrument is proportional to square of operating current, therefore the instrument has basically square law response. This instrument is one of the most primitive forms of measuring and relay instrument.
Inside the coil, there are two soft iron pieces rods or vanes placed parallel to each other and along the axis, of the coil. This principle is utilized in the moving iron repulsion type instrument. Jan 15, 2019 a permanent magnet moving coil pmmc meter also known as a darsonval meter or galvanometer is an instrument that allows you to measure the current through a coil by observing the coils angular deflection in a uniform magnetic field. Moving coil instrument working principle your electrical. Movingiron instruments are generally used to measure alternating. When current flows in the solenoid, a pivoted soft iron disc is attracted towards the solenoid and the movement causes a pointer to move across a scale.
An attraction type of moving iron instrument is shown diagrammatically in figure. The instrument having its deflection depends upon average value is. Whereas in moving coil instrument the conductor coil is used for dc measurement. The operation of the attraction type depends on the attraction of a single piece of soft iron into a magnetic field and that of repulsion type depends on the repulsion of two adjacent pieces of iron magnetised. Moving iron instrument working operation electrical edition. Attraction or single iron type figure 2 the brief description of different components of a moving iron instrument is given below. Capable of giving an accuracy within limits of both precision and industrial grades. Analog instruments classification of analog instruments. Construction of attraction type moving iron instrument. Both moving coil and moving iron instruments are used measure the voltage and current of circuits. The basic principle can also be stated that when a field resultant magnetic field produced by the movable current carrying coil tries to come in line with the main field. At one end of the coil, a ovalshaped soft iron disc is pivoted eccentrically so that it can be attracted into the coil and the pointer attacted to the disc can show reading. Figure below shows a simple moving iron instrument.
Moving iron instruments, classification of moving iron. The instrument which uses the soft iron piece as a moving element such. When the current to be measured is passed through the coil, then coil produces a magnetic field and attracts the ovalshaped disc, hence disc will swing into the coil. Oct 21, 2016 before answering your question let me explain the working principle of both moving coil and moving iron instruments that will give you a basic idea. Jul 21, 2014 the instrument can be constructed to measure current and voltage to an accuracy needed in most engineering works and still be cheaper as compared any other type of a. Construction of attraction type moving iron instruments. In moving iron instruments, a plate or van of soft iron or of high permeability steel forms the moving element of the system. Essentials of indicating instruments moving coil, moving iron, shunts and multipliers. Moving iron instrument multiple choice questions and answers. Classification of moving iron instruments a media to get. Construction of attraction type moving iron instruments points. Whenever a piece of iron is placed nearer to a magnet it would be attracted by the magnet. In the attraction type moving iron instrument, current is passed through the coil.
The basic moving coil instrument working principle is that when a current carrying conductor is placed in a magnetic field, a mechanical force is exerted on the conductor. Attraction type moving iron instrument by prof anil. The construction of the attraction type moving iron instrument is shown in the below figure. A small piece of soft iron in the form of a vane or rod. When a permanent magnet is brought near it, there will be either a force of attraction or repulsion. The deflection of moving iron instruments is independent of direction of current, because the needle of the moving iron instrumen. What is the difference between movingiron and movingcoil. Dec 25, 2014 construction of attraction type moving iron instruments points. Electrical technology playlist pl5fcg6tovhr493p0pd6m1uyh4yfbjozgj unit 1 millmans theorem. Attraction type moving iron instruments are commonly used and therefore, we will focus on it. Its range can be extended by using published on 10 sep 15. The attraction of iron pieces is independent of the direction of the current in the coil and thus named \unpolarised instrument, because of magnetisation of iron piece it will be experienced by a torque.
Apr 20, 2018 working principle of moving iron instruments. Working principle of moving iron instruments electrical. In repulsion type, a fixed vane or rod is also used and magnetized with the same polarity. When the current to be measured or a definite fraction of it or proportional to the voltage to be measured is passed through the solenoid, a magnetic field is set up inside the solenoid. Moving iron instruments having scales that are nonlinear and somewhat crowded in the lower range of calibration. The pointer is attached to the spindle so that it is deflected with the motion of.
Moving iron type instruments are of mainly two types. In repulsion type movingiron instrument consists of two cylindrical soft. Construction of attraction type instrument the stationary coil of the attraction type instrument is flat and has a narrow opening. An attraction type of movingiron instrument is shown diagrammatically in figure. Since the stationary parts and the moving parts of the instrument are simple so they are cheapest. Attraction or singleiron type figure 2 the brief description of different components of a movingiron instrument is given below. An oval shaped soft iron pieces is attached to the spindle in such a way that it can move in or out of the coil. Why do moving iron instruments measure both ac and dc. Construction and working of repulsion type moving iron construction and working of repulsion type moving iron. When this happens, coil produces magnetic field which attracts soft iron cam placed near to it. Classification of electrical measuring instruments.
The basic principle of a repulsion type moving iron instruments is that the repulsive forces will act when two similarly magnetized iron pieces, are placed near each other construction. The force of attraction acting on the soft iron core and the magnitude of the force depends on the strength of the magnetic field. Ferromagnetic materials magnetize in the direction of a magnetic field, therefore, if they are brought near one end of a current carrying coil. In this page you can learn various important moving iron instrument multiple choice questions answers,mcq on moving iron instrument with answers,mcq on moving iron instrument,sloved moving iron instrument objective questions answers etc. Feb 01, 2017 4 constructional details of attraction type mi moving element. Pdf classification of moving iron instruments atul. Jul 25, 2018 this instrument is one of the most primitive forms of measuring and relay instrument. In dc, only the coil resistance is the opposition to current flow. To this iron a pointer is attached so that it may deflect along with the moving iron over a graduated scale.
Types of ammeters, voltmeters electrical instruments. The attraction and the repulsion are the types of the moving iron instruments. It consists of a hollow cylindrical coil or solenoid which is kept fixed as shown in the fig. Moving coil instrument working principle your electrical guide. Thus attraction type moving iron instruments can be used on ac as well as on dc systems. Moving iron instruments principle, operation and type, theory. K l university department of basic engineering sciences1.
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