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. Classification of moving iron instrument moving iron instrument are of two types attraction type repulsion type 4. 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. Analog instruments classification of analog instruments. Moving iron instrument working operation electrical edition. When the coil is excited it produces magnetic field. 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. Positive current in the coil has the same pull as negative current. A few instruments belong to a third combination type. There are two general types of movingiron instruments namely i repulsion or double iron type ii attraction or singleiron type.
Attraction type construction of the attraction type moving iron instrument is as shown in the given figure. If there were no saturation, the change of inductance with the angle of deflection i. The attraction type instruments use spring, which provided the controlling torque. The attraction and the repulsion are the types of the moving iron instruments. The movement is light, quick acting, but extremely robust. Classification, absolute and secondary instruments, indicating instruments, control, balancing and damping, constructional details, characteristics, errors in measurement, ammeters, voltmeters. Moving iron instruments attraction type and repulsion type. Moving iron instruments principle, operation and type. The instruments developed by us have an almost uniform scale starting at 10% of the fullscale reading. Suitable for low frequency and high power circuits. The majority of movingiron instruments are either of the attraction type or of the repulsion type. The most widely used movingiron instruments are switchboard instruments of classes 1. In this also consists of soft iron which is of movable and fixed coils. The basic working principle of moving iron attraction typeis very these instruments simple that a soft iron piece if instrument brought near the magnet gets.
The movingiron meter was invented by austrian engineer friedrich drexler in 1884. Click here to download the pdf of this topic moving iron instruments. Moving iron instrument working principle, construction. The deflection of the coil is reduced by the aluminium piston which is attached to the moving coil. 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. For such pure square response, moving iron instrument scale can easily be graduated uniformly.
What is the difference between movingiron and movingcoil. Construction of attraction type moving iron instrument. Moving iron instruments principle and operation repulsion type. Deflecting torque in the attraction type moving iron instrument, the deflecting torque is due to the force of. Moving iron instruments attraction and repulsion type. Moving iron instruments attraction type and repulsion type complete concept duration.
In moving iron instruments, a plate or van of soft iron or of high permeability steel forms the moving element of the system. Pdf moving coil or moving iron controllable actuators. Movingiron measuring mechanisms are also used in ratio meters. Again moving iron classified as attraction and repulsion types of instruments. In repulsion type, a fixed vane or rod is also used and magnetized with the same polarity. Moving iron type instruments are of mainly two types. 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. Electromagnetic instruments are divided into simple moving iron, dynamo meter type and induction types of instruments.
This field attracts the eccentrically mounted vane on the spindle towards it. Moving iron ammeters use a piece of iron which moves when acted upon by the electromagnetic force of a fixed coil of wire. The figure shows an attraction type moving iron mi instrument. Permanent magnet moving coil or pmmc instrument definition. Repulsion type instruments the repulsion type instrument has two vanes. 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. The deflecting torque causes the moving system to move from its zero position. What does the moving iron voltmeter measure in a circuit. 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. It consists of a hollow cylindrical coil or solenoid which is kept fixed as shown in the fig. Moving iron springmounted jewel bearing suspension accuracy.
The basic working principle of these instruments is very simple that a soft iron piece if brought near magnet gets attracted by the magnet. The magnetic field induces by the electromagnet whose strength depends. There are two general types of moving iron instruments namely. One important requirement in indicating instruments is the arrangement for producing operating or deflecting torque t d when the instrument is connected in the circuit to measure the given electrical quantity. Capable of giving an accuracy within limits of both precision and industrial grades. This is achieved by utilizing the various effects of electric current or voltage. 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. Moving iron instruments are generally used for measuring ac voltage and currents. The force of attraction depends on the strength of the magnet field.
Pdf eec 126 instrumentation theory farouq osuolale. 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 brief description of different components of a movingiron instrument is given below. It operates on the principle that the torque is exerted on the moving coil placed in the field of the permanent magnet. There are two general types of movingiron instruments namely. If two soft iron pieces are place near a current carrying coil there will be a force of repulsion. For low voltage range the power consumption is higher. Both moving coil and moving iron instruments are used measure the voltage and current of circuits. Classification of moving iron instruments a media to. This principle is used in moving iron attraction type instrument.
Voltmeters types of voltmeters with brief explanation. What is permanent magnet moving coil or pmmc instrument. Construction and working of repulsion type moving iron construction and working of repulsion type moving iron. Name the bridge used to measure low value resistance 4 how. The pointer is attached to the spindle so that it is deflected with the motion of. A small piece of soft iron in the form of a vane or rod. 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 the simplest form of attraction type moving iron instrument uses a solenoid and a moving oval shaped soft iron pivoted eccentrically. A soft iron vane iv is attached to the moving system. This type of meter responds to both direct and alternating currents as opposed to the movingcoil ammeter, which works on. 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 instrument having its deflection depends upon average value is. Moving iron instrument this instrument is one of the most primitive forms of measuring and relay instrument. The iron van is so situated that it can move in the magnetic field produced by a stationary coil. While moving iron instruments are used in ac circuits. It works on the principle that the iron place near the magnet attracts towards it.
Construction of attraction type moving iron instruments. Moving ironmi instruments the moving iron instruments are classified as. Attraction type the construction of an attraction type moving iron instrument. The instruments which use the permanent magnet for creating the stationary magnetic field between which the coil moves is known as the permanent magnet moving coil or pmmc instrument. The current to be measured is passed through the coil, coil produced the magnetic field. The instrument in which the moving iron is used for measuring the flow of current or voltage is known as the moving iron instrument. Which of the following instruments can be used for full scale deflection of 300o. Find details of companies offering moving iron ammeter at best price. But in actual instrument rate of change of inductance with angular deflection i. This instrument is one of the most primitive forms of measuring and relay instrument. Its range can be extended by using published on 10 sep 15.
Current in one direction through the wire will produce a clockwise torque on the needle mechanism, while current the other direction will produce a counterclockwise torque. The usual moving iron actuators are more generally. Figure below shows a simple moving iron instrument. A moving iron meter doesnt have a permanent magnet it relies on the magnetic attraction from the current in the coil to pull a piece of iron. The effect is utilised in the attraction type of moving iron instruments.
Whenever a piece of iron is placed nearer to a magnet it would be attracted by the magnet. To study the advantage and errors involved in movingiron instruments. 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. 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 force of this attraction depends upon the strength said magnetic. As far as we know such instruments are not being produced anywhere.
When the current to be measured is passed through the coil c, a magnetic field is produced. 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. Advantages and disadvantages of movingiron instruments. Since the stationary parts and the moving parts of the instrument are simple so they are cheapest. Get complete concept after watching this video topics covered under playlist of electrical measuring instruments. In repulsion type, a fixed vane or rod is also used and magnetized with the. In attraction type moving iron instruments, an ovalshaped disc made up of soft iron is pivoted on the spindle near the coil. Moving iron instruments principle, operation and type, theory of. Construction of attraction type moving iron instruments points. Working principle of moving iron instruments electrical. 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. The coil is flat and has a narrow slot like opening the moving iron disc or a sector essentially mounted. The construction of the attraction type moving iron instrument is shown in the below figure. An attraction type of movingiron instrument is shown diagrammatically in figure.
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