Moving iron instruments attraction type and repulsion type. Feb 15, 2012 classification of moving iron instrument. This is also called ferraris type instrument and is shown in the fig. 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. There are two general types of moving iron instruments namely i repulsion or double iron type ii attraction or single iron type. 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.
Coils are wound on the poles, the opposite poles being connected in series. In moving iron instruments, a plate or van of soft iron or of high permeability steel forms the moving element of the system. The effect is utilised in the attraction type of moving iron instruments. Thus moving iron instruments are unpolarised instruments. An instrument to be used for measurement and control should preferably have a. These instruments use soft iron which is a ferromagnetic material. The instrument in which the coil rotates between the magnetic field of the permanent magnet for measuring the dc such type of instrument is known as the moving coil instrument. The main elements of a movingiron instrument are a measuring circuit that converts the quantity to be measured into a dc or ac current and a. Classification, absolute and secondary instruments, indicating instruments, control, balancing and damping, constructional details, characteristics, errors in measurement, ammeters, voltmeters. If two soft iron pieces are place near a current carrying coil there will be a force of repulsion. The force of attraction depends on the strength of the magnet field.
To this iron a pointer is attached so that it may deflect along with the moving iron over a graduated scale. Apr 20, 2018 for such pure square response, moving iron instrument scale can easily be graduated uniformly. The movement is light, quick acting, but extremely robust. Disadvantages of electrodynamic instruments 49 35 movingiron instruments 49 attraction type movingiron instrument 49 concentricvane movingiron instrument 51 torque equation 51 advantages of movingiron instruments 52 disadvantages of movingiron instruments 52 2irug8qlyhuvlw\3uhvv. Whereas the hysteresis loss occurs in the moving coil instrument. But in actual instrument rate of change of inductance with angular deflection i. Electrostatic type instruments construction principle.
When the current to be measured is passed through the coil c, a magnetic field is produced. Moving iron instruments attraction and repulsion type. Figure below shows a simple moving iron instrument. The pointer is attached to the spindle so that it is deflected with the motion of. For low voltage range the power consumption is higher. Repulsion type instruments the repulsion type instrument has two vanes or iron plates. The meter readings are affected by hysteresis error, changes of frequency and wave forms the accuracy of the readings is affected by stray magnetic fields. Moving iron instruments principle and operation repulsion type. Difference between moving coil instrument,moving iron instrument. When you go for viva or interview most often question on electrical measurements is what is the difference between mi and mc type instruments.
Movingcoil instrument article about movingcoil instrument. In repulsion type movingiron instrument consists of two cylindrical soft. 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. Explanation of errors in moving iron instruments blogger. Both moving coil and moving iron instruments are used measure the voltage and current of circuits. 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. The magnetic field induces by the electromagnet whose. The brief description of different components of a moving iron instrument is given below. When one of the plates is fixed and other plate is free to move, plates are oppositely charged in order to have attractive force between them. Moving iron instrument multiple choice questions and answers.
Whenever a piece of iron is placed nearer to a magnet it would be attracted by the magnet. The instrument in which the moving iron is used for measuring the flow of current or voltage is known as the moving iron instrument. Moving iron instrument working operation electrical edition. Moving iron instrument this instrument is one of the most primitive forms of measuring and relay instrument. The deflection of the coil is reduced by the aluminium piston which is attached to the moving coil.
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. When this happens, coil produces magnetic field which attracts soft iron cam placed near to it. Moving iron measuring mechanisms are also used in ratio meters. An analog instrument is one in which the output or display is a continuous function of time and bears a constant relation to its input. Class 3 for bimetallic meter movements and class 1.
The coil is flat and has a narrow slot like opening the moving iron disc or a sector essentially mounted. Analog instruments find extensive use in present day applications although digital instruments are increasing in number and applications. Name the bridge used to measure low value resistance 4 how inductance is from eee 01 at psg college of technology. Moving coil instrument working principle your electrical. A soft iron vane iv is attached to the moving system. There are two general types of movingiron instruments namely i repulsion or double iron type ii attraction or singleiron type. Let us have a comparison between two major type of electrical measuring instruments they are moving coil mc and moving iron mi instruments. A small piece of soft iron in the form of a vane or rod. This principle is used in moving iron attraction type instrument. Any instrument in which current is sent through one or more coils suspended or pivoted in a magnetic field, and the motion of the coils is used to measure either the current in the coils or the strength of the field. The repulsion type instrument is a nonpolarized instrument, i.
Fig shows the constructional details of an attraction type mi instrument. Moving iron instrument working principle, construction, advantage and disadvantages in hindi. The areas of application which are common to both analog and digital instruments are fairly limited at. Construction and working of repulsion type moving iron construction and working of repulsion type moving iron. The moving iron instrument is free from the hysteresis loss.
Jul 21, 2014 attraction type the construction of an attraction type moving iron instrument. The deflection of moving iron instruments is independent of direction of current, because the needle of the moving iron instrumen. When the coil is excited it produces magnetic field. Movingiron instrument article about movingiron instrument. What is the difference between movingiron and movingcoil. In this type of instrument, the coil is stationery and the deflection is caused by a soft iron piece moving in the field produced by the coil. The current coil of a wattmeter is connected to the. The angular deflection of needle of moving iron instruments is related to the current flowing through the field coil. It consists of a hollow cylindrical coil or solenoid which is kept fixed as shown in the fig. Capable of giving an accuracy within limits of both precision and industrial grades. Moving coil instruments there are two types of moving coil instruments namely, permanent magnet moving coil type which can only be used for direct current, voltage measurements and the dynamometer type which can be used on either direct or alternating current, voltage measurements.
As the name suggests the electrostatic type instrument use static electrical field to produce the deflecting torque. The attraction type instruments use spring, which provided the controlling torque. Moving iron instruments are generally used for measuring ac voltage and currents. 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.
Analog instruments classification of analog instruments. The force of this attraction depends upon the strength said magnetic. Now due this attractive force movable plate will move towards the stationary or fixed plate till the moving plate stored maximum electrostatic energy. 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. Electrostatic type instruments construction principle torque. Moving iron instruments principle, operation and type. Moving iron instruments attraction type easiest explained. Jul 25, 2018 construction of electrostatic type instruments. Attraction type moving iron instruments are commonly used and therefore, we will focus on it. State the disadvantages of moving iron instruments.
A feature of the moving element is that it is fitted with synthetic sapphire jewels. This field attracts the eccentrically mounted vane on the spindle towards it. Measurement of voltage and current what is the use. Thus attraction type moving iron instruments can be used on ac as well as on dc systems. This instrument is one of the most primitive forms of measuring and relay instrument. Differences between moving coil mc and moving iron mi. A hollow circular coil is used and one of the iron pieces is attached inside the hollow coil. The most widely used moving iron instruments are switchboard instruments of classes 1. The instrument having its deflection depends upon average value is. The brief description of different components of a movingiron instrument is given below. The coils on the two pairs of poles are connected in parallel.
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. Construction of attraction type moving iron instruments points. 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. The figure shows an attraction type moving iron mi instrument. Deflection torque is proportional to the square of the current. Working principle of moving iron instruments electrical. These types of instrument are generally used for the measurement of high voltages but in some cases they can be used in measuring the lower voltages and powers of a given circuit. Suitable for low frequency and high power circuits. The latter instruments may be used for frequencies of up to 800 hertz.
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. Ferromagnetic materials magnetize in the direction of a magnetic field, therefore, if they are brought near one end of a current carrying 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. One iron vane is held fixed to the coil frame and other is free to rotate, carrying with it. It consists of a laminated magnet with the pairs of poles at right angles to each other. Attraction type construction of the attraction type moving iron instrument is as shown in the given figure.
Movingiron instrument a measuring instrument whose operation is based on the interaction between a magnetic field that is proportional to the quantity to be measured and a core made of a ferromagnetic material. The magnetic field induces by the electromagnet whose strength depends. 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. Since the stationary parts and the moving parts of the instrument are simple so they are cheapest. Jul 25, 2018 this instrument is one of the most primitive forms of measuring and relay instrument. It consists of a fixed cylindrical hollow coil which carries the operating current. Electrical technology playlist pl5fcg6tovhr493p0pd6m1uyh4yfbjozgj unit 1 millmans theorem. One iron vane is held fixed to the coil frame and other is free to rotate.
The instrument in which the moving iron is used for measuring the flow of current. 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. Construction of attraction type moving iron instruments. 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. Moving iron instrument working principle, construction. Advantages and disadvantages of movingiron instruments. Name the bridge used to measure low value resistance 4 how. It works on the principle that the iron place near the magnet attracts towards it. H mi instruments may be seriously affected by waveform both on account of the change in the form of flux waveform and in case of voltmeter, the effect of harmonic upon the inductance. Classification of moving iron instrument moving iron instrument are of two types attraction type repulsion type 4. 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. Difference between moving coil instrument,moving iron.
The iron van is so situated that it can move in the magnetic field produced by a stationary coil. Thus moving iron instruments are unpolarised instruments i. Moving iron mi instruments generally used to measure ac current or voltage but can measure dc current and voltage without any external circuit pointer is connected to specially designed soft iron that moves according to the intensity of magnetic field acting on it the magnetic field is produced by current carrying coil. Classification of moving iron instruments a media to get. Why do moving iron instruments measure both ac and dc. The current to be measured is passed through the coil, coil produced the magnetic field. Get complete concept after watching this video topics covered under playlist of electrical measuring instruments. 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. 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. It works on the principle that the force acting on the coil places between the magnetic field of the. 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. Apr 20, 2018 in moving iron instruments, a van of soft iron forms the moving element of the system.
An attraction type of moving iron instrument is shown diagrammatically in figure. Moving iron instruments are generally used to measure alternating voltages and currents. There are two general types of moving iron instruments namely. Moving iron instruments principle, operation and type, theory of. The construction of the attraction type moving iron instrument is shown in the below figure. 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. There are two general types of movingiron instruments namely. Learn what moving iron instruments are, a working animation, how they are constructed, and. The instrument which uses the soft iron piece as a moving element such type of instrument is known as the mi instrument. Moving iron instruments principle, operation and type, theory. Working principle of electrostatic type instruments. Which of the following instruments can be used for full scale deflection of 300o. The moving iron instrument can be used as an ammeter, voltmeter and wattmeter. In this article all major differences between moving iron and moving coil instruments are discussed.
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