The effect is utilised in the attraction type of moving iron instruments. One iron vane is held fixed to the coil frame and other is free to rotate. 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. 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. Working principle of moving iron instruments electrical. 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. What is the difference between movingiron and movingcoil. Differences between moving coil mc and moving iron mi. 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 and working of repulsion type moving iron construction and working of repulsion type moving iron. Moving iron measuring mechanisms are also used in ratio meters. Working principle of electrostatic type instruments.
Name the bridge used to measure low value resistance 4 how inductance is from eee 01 at psg college of technology. 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. 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. For low voltage range the power consumption is higher. Moving iron instruments principle, operation and type. When this happens, coil produces magnetic field which attracts soft iron cam placed near to it.
This is also called ferraris type instrument and is shown in the fig. 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. The magnetic field induces by the electromagnet whose. A small piece of soft iron in the form of a vane or rod. Attraction type construction of the attraction type moving iron instrument is as shown in the given figure. Apr 20, 2018 for such pure square response, moving iron instrument scale can easily be graduated uniformly. Electrostatic type instruments construction principle torque. Ferromagnetic materials magnetize in the direction of a magnetic field, therefore, if they are brought near one end of a current carrying coil. Click here to download the pdf of this topic moving iron instruments. The pointer is attached to the spindle so that it is deflected with the motion of. 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.
The movement is light, quick acting, but extremely robust. 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. Let us have a comparison between two major type of electrical measuring instruments they are moving coil mc and moving iron mi instruments. The angular deflection of needle of moving iron instruments is related to the current flowing through the field coil. 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. In moving iron instruments, a plate or van of soft iron or of high permeability steel forms the moving element of the system. An attraction type of movingiron instrument is shown diagrammatically in figure. Jul 25, 2018 this instrument is one of the most primitive forms of measuring and relay instrument. Due to this, moving iron instrument scale gets distorted from the square law. 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. Moving iron instrument working operation electrical edition. Classification of moving iron instruments a media to get. Measurement of voltage and current what is the use. The repulsion type instrument is a nonpolarized instrument, i.
Its range can be extended by using published on 10 sep 15. The instrument having its deflection depends upon average value is. Moving iron instruments attraction type easiest explained. The deflection of the coil is reduced by the aluminium piston which is attached to the moving coil. This field attracts the eccentrically mounted vane on the spindle towards it. Moving iron instruments attraction and repulsion type.
When the coil is excited it produces magnetic field. The latter instruments may be used for frequencies of up to 800 hertz. 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. There are two general types of movingiron instruments namely i repulsion or double iron type ii attraction or singleiron type. The instrument in which the moving iron is used for measuring the flow of current or voltage is known as the moving iron instrument. Suitable for low frequency and high power circuits. Advantages and disadvantages of movingiron instruments. 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. Thus moving iron instruments are unpolarised instruments.
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 moving iron instruments is independent of direction of current, because the needle of the moving iron instrumen. Which of the following instruments can be used for full scale deflection of 300o. 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. In repulsion type movingiron instrument consists of two cylindrical soft. 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. These instruments use soft iron which is a ferromagnetic material. Fig shows the constructional details of an attraction type mi instrument. 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. Electrical technology playlist pl5fcg6tovhr493p0pd6m1uyh4yfbjozgj unit 1 millmans theorem.
When the current to be measured is passed through the coil c, a magnetic field is produced. But in actual instrument rate of change of inductance with angular deflection i. 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. The instrument which uses the soft iron piece as a moving element such type of instrument is known as the mi instrument. Construction of attraction type moving iron instruments points. The current coil of a wattmeter is connected to the. Feb 15, 2012 classification of moving iron instrument. Movingcoil instrument article about movingcoil instrument. Moving iron instrument this instrument is one of the most primitive forms of measuring and relay instrument. Since the stationary parts and the moving parts of the instrument are simple so they are cheapest. When you go for viva or interview most often question on electrical measurements is what is the difference between mi and mc type instruments. Moving iron instruments are generally used for measuring ac voltage and currents.
Analog instruments classification of analog instruments. Analog instruments find extensive use in present day applications although digital instruments are increasing in number and applications. The attraction type instruments use spring, which provided the controlling torque. Whenever a piece of iron is placed nearer to a magnet it would be attracted by the magnet. In this article all major differences between moving iron and moving coil instruments are discussed. The iron van is so situated that it can move in the magnetic field produced by a stationary coil. Moving iron instruments principle, operation and type, theory of.
Classification, absolute and secondary instruments, indicating instruments, control, balancing and damping, constructional details, characteristics, errors in measurement, ammeters, voltmeters. The force of this attraction depends upon the strength said magnetic. Moving iron instrument working principle, construction, advantage and disadvantages in hindi. A feature of the moving element is that it is fitted with synthetic sapphire jewels. 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. Moving iron instruments attraction type and repulsion type.
It consists of a hollow cylindrical coil or solenoid which is kept fixed as shown in the fig. The magnetic field induces by the electromagnet whose strength depends. In the attraction type moving iron instrument, current is passed through the coil. 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. Thus attraction type moving iron instruments can be used on ac as well as on dc systems. The coil is flat and has a narrow slot like opening the moving iron disc or a sector essentially mounted.
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. As the name suggests the electrostatic type instrument use static electrical field to produce the deflecting torque. Thus moving iron instruments are unpolarised instruments i. Construction of attraction type moving iron instrument.
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. Jul 21, 2014 attraction type the construction of an attraction type moving iron instrument. Coils are wound on the poles, the opposite poles being connected in series. Movingiron instrument article about movingiron instrument.
One iron vane is held fixed to the coil frame and other is free to rotate, carrying with it. 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. The current to be measured is passed through the coil, coil produced the magnetic field. Moving coil instrument working principle your electrical. Learn what moving iron instruments are, a working animation, how they are constructed, and. Attraction type moving iron instruments are commonly used and therefore, we will focus on it. Moving iron instrument multiple choice questions and answers. Difference between moving coil instrument,moving iron instrument. 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. Why do moving iron instruments measure both ac and dc. 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. State the disadvantages of moving iron instruments. Electrostatic type instruments construction principle. The construction of the attraction type moving iron instrument is shown in the below figure.
An attraction type of moving iron instrument is shown diagrammatically in figure. The instrument in which the moving iron is used for measuring the flow of current. 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. Difference between moving coil instrument,moving iron. 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. If two soft iron pieces are place near a current carrying coil there will be a force of repulsion. The figure shows an attraction type moving iron mi 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. 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. There are two general types of moving iron instruments namely i repulsion or double iron type ii attraction or single iron type. The brief description of different components of a movingiron instrument is given below. Construction of attraction type moving iron instruments.
Moving iron instruments principle, operation and type, theory. 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. Explanation of errors in moving iron instruments blogger. Apr 20, 2018 in moving iron instruments, a van of soft iron forms the moving element of the system. It consists of a laminated magnet with the pairs of poles at right angles to each other. Moving iron type instruments are of mainly two types.
It works on the principle that the iron place near the magnet attracts towards it. The basic working principle of these instruments is very simple that a soft iron piece if brought near magnet gets attracted by the magnet. There are two general types of movingiron instruments namely. The coils on the two pairs of poles are connected in parallel. Jul 25, 2018 construction of electrostatic type 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. Capable of giving an accuracy within limits of both precision and industrial grades. 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. This instrument is one of the most primitive forms of measuring and relay instrument. Class 3 for bimetallic meter movements and class 1. Now due this attractive force movable plate will move towards the stationary or fixed plate till the moving plate stored maximum electrostatic energy. The moving iron instrument can be used as an ammeter, voltmeter and wattmeter.
The most widely used moving iron instruments are switchboard instruments of classes 1. Inside the coil, there are two soft iron pieces rods or vanes placed parallel to each other and along the axis, of the coil. Moving iron instrument working principle, construction. The moving iron instrument is free from the hysteresis loss. The brief description of different components of a moving iron instrument is given below. Deflection torque is proportional to the square of the current. Get complete concept after watching this video topics covered under playlist of electrical measuring instruments. The force of attraction depends on the strength of the magnet field. Both moving coil and moving iron instruments are used measure the voltage and current of circuits. Moving iron instruments principle and operation repulsion type. Figure below shows a simple moving iron instrument. Classification of moving iron instrument moving iron instrument are of two types attraction type repulsion type 4. Name the bridge used to measure low value resistance 4 how.