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. Sep 05, 2012 moving iron instruments there are of two types of moving iron instruments. The instrument having its deflection depends upon average value is. A small piece of soft iron in the form of a vane or rod.
The effect is utilised in the attraction type of moving iron instruments. Classification of moving iron instruments a media to. When the current flows through the coil a magnetic field is produced and the moving iron moves from the weaker field outside the coil to the stronger. Classification of moving iron instruments moving iron instruments are of two types i attraction type. There are two general types of movingiron instruments namely. When the current to be measured is passed through the coil c, a magnetic field is produced. Classification, absolute and secondary instruments, indicating instruments, control, balancing and damping, constructional details, characteristics, errors in measurement, ammeters, voltmeters. K l university department of basic engineering sciences1. Construction of attraction type moving iron instruments points.
This field attracts the eccentrically mounted vane on the spindle towards it. The attraction and the repulsion are the types of the moving iron instruments. Jul 25, 2018 this instrument is one of the most primitive forms of measuring and relay instrument. Whereas in moving coil instrument the conductor coil is used for dc measurement. Its range can be extended by using published on 10 sep 15. The basic working principle of these instruments is very simple that a soft iron piece if brought near magnet gets attracted by the magnet. Electrical technology playlist pl5fcg6tovhr493p0pd6m1uyh4yfbjozgj unit 1 millmans theorem. In both the attraction and repulsion type moving iron 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. To this iron a pointer is attached so that it may deflect along with the moving iron over a graduated scale. There are two general types of moving iron instruments namely. Attraction type the construction of an attraction type moving iron instrument. 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. Which of the following instruments can be used for full scale deflection of 300o.
Classification of moving iron instruments a media to get. Moving iron instruments principle, operation and type, theory. Construction of attraction type moving iron instruments. Disadvantages of electrodynamic instruments 49 35 moving iron instruments 49 attraction type moving iron instrument 49 concentricvane moving iron instrument 51 torque equation 51 advantages of moving iron instruments 52 disadvantages of moving iron instruments 52 2irug8qlyhuvlw\3uhvv. Apr 20, 2018 in moving iron instruments, a van of soft iron forms the moving element of the system. Therefore, if we pivot the soft iron on a spindle between two bearings and a coil is mounted near it, the iron piece will swing into the coil when the latter is carrying current. Attraction type in this type of instrument, a single soft iron vane moving iron is mounted on the spindle, and is attracted towards the coil when operating current flows through it. In moving iron instruments the movable system consists of one or more pieces of speciallyshaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil. Repulsion type instruments the repulsion type instrument has two vanes or iron plates. The deflection of the coil is reduced by the aluminium piston which is attached to the moving coil. Click here to download the pdf of this topic moving iron instruments. The force of this attraction depends upon the strength said magnetic. Jul 21, 2014 attraction type the construction of an attraction type moving iron instrument. The pointer is attached to the spindle so that it is deflected with the motion of the soft iron piece.
Construction and working of repulsion type moving iron construction and working of repulsion type moving iron. This principle is utilized in the moving iron repulsion type instrument. For low voltage range the power consumption is higher. These are similarly magnetized when the current flows through the coil and there is a force of repulsion between the two vanes resulting in the movement of the moving vane. Moving iron instruments attraction type easiest explained. Analog instruments classification of analog instruments. A few instruments belong to a third combination type. 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. 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 following types of instruments are used for dual purpose. To produce the magnetic field due to current flowing through it and also to magnetize the. 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. Thus attraction type moving iron instruments can be used on ac as well as on dc systems. The operation of a permanentmagnet moving coil 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. The attraction type instruments use spring, which provided the controlling torque. The moving iron instrument can be used as an ammeter. Moving iron instruments there are of two types of moving iron instruments. It consists of a fixed cylindrical hollow coil which carries the operating current. Home advantages and disadvantages of movingiron instruments. The brief description of different components of a moving iron instrument is given below. Pdf classification of moving iron instruments atul. Repulsion type instruments the repulsion type instrument has two vanes. Moving iron instruments, classification of moving iron.
Attraction type, repulsion type moving iron ammeter pdf. When the coil is excited it produces magnetic field. Oct 14, 2017 moving iron instruments attraction type and repulsion type complete concept duration. Why do moving iron instruments measure both ac and dc. An attraction type of moving iron instrument is shown diagrammatically in figure. In moving iron instruments, the gravity or spring provides the controlling torque to the instrument. Moving coil instrument working principle your electrical guide. The control torque is provided by two hairsprings s1 and s2 in the same way as for a pmmc instrument, but in such instruments, springs are not used to carry any current gravity control can also be used for vertically mounted panel type mi meters. 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. Moving iron instrument working operation electrical edition. Disadvantages of electrodynamic instruments 49 35 movingiron instruments 49 attractiontype movingiron instrument 49 concentricvane movingiron instrument 51 torque equation 51 advantages of movingiron instruments 52 disadvantages of movingiron instruments 52 2irug8qlyhuvlw\3uhvv. A soft iron vane iv is attached to the moving system. Thus moving iron instruments are unpolarised instruments i. There are two general types of moving iron instruments namely i repulsion or double iron type ii attraction or single iron type.
In attraction type moving iron instruments, an ovalshaped disc made up of soft iron is pivoted on the spindle near the coil. 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. The angular deflection of needle of moving iron instruments is related to the current flowing through the field coil. Feb 15, 2012 classification of moving iron instrument. In this system, when current flows through the coil, a magnetic field. The deflection of needle of moving iron instrument is given in terms of rms value of voltage or current. Moving iron instruments principle and operation repulsion type damping torque deflecting torque theory of attraction type moving iron instrument. Moving iron instruments principle, operation and type, theory of. Ferromagnetic materials magnetize in the direction of a magnetic field, therefore, if they are brought near one end of a current carrying coil. An attraction type of movingiron instrument is shown diagrammatically in figure. The figure shows an attraction type moving iron mi instrument. The construction of the attraction type instrument is shown in the. Essentials of indicating instruments moving coil, moving iron, shunts and multipliers. Movingiron measuring mechanisms are also used in ratio meters.
The pointer is attached to the spindle so that it is deflected with the motion of. 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. The most widely used movingiron instruments are switchboard instruments of classes 1. Ferromagnetic materials magnetize in the direction of a magnetic field, therefore, if they are brought near one end of a current carrying coil, poles of opposite polarity are induced in them. What is the difference between movingiron and movingcoil. These instruments use soft iron which is a ferromagnetic material. 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. 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. Types of ammeters, voltmeters electrical instruments. Moving coil instrument working principle your electrical.
Moving iron instrument multiple choice questions and answers. 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. Dec 25, 2014 construction of attraction type moving iron instruments points. Advantages, disadvantages, errors in moving iron instrument. In moving iron instruments, a van of soft iron forms the moving element of the system. Feb 01, 2017 4 constructional details of attraction type mi moving element. 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. Attraction type moving iron instruments these instruments use soft iron which is a ferromagnetic material. On passing current through the coil produces magnetic field which attracts soft. The damping torque is provided by the movement of a thin vane v in a closed sectorshaped box b, or. If two soft iron pieces are place near a current carrying coil there will be a force of repulsion. This principle is used in moving iron attraction type instrument. 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. The deflection of moving iron instruments is independent of direction of current, because the needle of the moving iron instrumen.
The brief description of different components of a movingiron instrument is given below. The basic working principle of attraction type moving iron instruments is illustrated in fig. Suitable for low frequency and high power circuits. Since the stationary parts and the moving parts of the instrument are simple so they are cheapest. Construction of attraction type moving iron instrument. Attraction type moving iron instruments are commonly used and therefore, we will focus on it. Moving iron instruments attraction and repulsion type. In movingiron instruments the movable system consists of one or more pieces of speciallyshaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil. The instrument in which the moving iron is used for measuring the flow of current. Both moving coil and moving iron instruments are used measure the voltage and current of circuits. Deflection torque is proportional to the square of the current. Whenever a piece of iron is placed nearer to a magnet it would be attracted by the magnet. 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. Moving iron instruments attraction type and repulsion type complete concept duration.
A hollow circular coil is used and one of the iron pieces is attached inside the hollow coil. 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. In the repulsion type, there are two vanes inside the coil. The majority of movingiron instruments are either of the attraction type or of the repulsion type. It is a permanent magnet moving coil instrument plus a rectifier is also suitable for acdc measurements. Due to this square law response, the moving iron instrument scale is nonuniform. The instrument which uses the soft iron piece as a moving element such type of instrument is known as the mi instrument. The coil is flat and has a narrow slot like opening the moving iron disc or a sector essentially mounted. Advantages and disadvantages of movingiron instruments. List out the instruments used to measure voltage and current. It consists of a hollow cylindrical coil or solenoid which is kept fixed as shown in the fig.
Moving iron type instruments are of mainly two types. Moving iron instruments principle, operation and type. 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. The attraction type, where the iron vane is drawn into the field of the coil as the current is increased, is shown schematically in figure 7. There are two general types of movingiron instruments namely i repulsion or double iron type ii attraction or singleiron type. As the angular deflection of moving iron instrument is proportional to square of operating current, therefore the instrument has basically square law response. Working principle of moving iron instruments electrical.
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. 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. 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. The iron van is so situated that it can move in the magnetic field produced by a stationary coil. The construction of the attraction type moving iron instrument is shown in the below figure. 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. Attraction type construction of the attraction type moving iron instrument is as shown in the given figure. Inside the coil, there are two soft iron pieces rods or vanes placed parallel to each other and along the axis, of the coil.
Capable of giving an accuracy within limits of both precision and industrial grades. This instrument is one of the most primitive forms of measuring and relay instrument. The current to be measured is passed through the coil, coil produced the magnetic field. Electrical technology playlist unit 1 millmans theorem.
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