Dynamometer type wattmeter construction and working. The force of attraction depends on the strength of the magnet field. Enter the page to learn more about electrical machines. May 12, 2018 permanent magnet moving coil or pmmc instruments are the most accurate type for the measurement of dc current or voltage. 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 construction and working principle in hindi duration. Construction and working of repulsion type moving iron construction and working of repulsion type moving iron. Analog instruments depend for their operation on one of the many effects produced by current and voltage and thus analog instruments are classified according to which of the effects is used for their working.
Moving coil galvanometer is an electromagnetic device that can measure small values of current. To study the advantage and limitation of pmmc instruments. It is capable of a machining heavy workpiece, which cannot be fit on a shaper table. Power factor meter working principle the basic working principle of power factor meter is similar to that of dynamometer type wattmeter i. Electrostatic type instruments construction principle. Moving iron type instruments are of mainly two types. This page includes all articles published in related to electrical machines. For example, an instrument meant for measurement of current is classified as an ammeter while an instrument that measures voltage is classified as a voltmeter. When a current carrying coil is placed in the magnetic field produced by permanent magnet, the coil experiences a force and moves.
The iron van is so situated that it can move in the magnetic field produced by a stationary coil. Pmmc instruments construction and working principle. Electrostatic type instruments construction principle torque. 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. Rectifier transformer working principle and application.
Voltmeters types of voltmeters with brief explanation and. 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 can measure current and voltage to a great accuracy. Attraction type the basic working principle of attraction type moving iron instruments is illustrated in fig. These instruments are based on the principle that when an unmagnetised soft iron piece is placed in the magnetic field of a coil, then the piece is attracted towards the coil. The iron van is so situated that it can move in the. It works on the principle that the iron place near the magnet attracts towards it. Whenever a piece of iron is placed nearer to a magnet it would be attracted by the magnet. The deflection of the moving system is indefinite if there is no controlling torque this torque opposes the deflecting torque and increases with the deflection of the moving system the pointer is brought to rest when these two torques are equal under the influence of controlling torque the pointer will return to its zero position on removing the source. Movingiron instruments construction and basic principle operation movingiron instruments are generally used to measure alternating voltages and currents. The moving iron instruments or mi instruments are quite cheap in cost, simple in construction and very accurate at fixed power supply frequency. This instrument is one of the most primitive forms of measuring and relay instrument. Jan 28, 2019 friends is video me ham moving iron instrument ke bare me discuss kar rahe hai, is video me apko moving iron instrument ke working principle, construction, advantage and disadvantages ke bare me.
Range extension of ammeters voltmeters your electrical. 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. They are used on board to assist in regular maintenance of electrical equipment or when precise measurements are required. The pmmc stands for permanent magnet moving coil and it is also called as darsonval instruments. Moving iron instruments moving iron instruments are generally used to measure alternating voltages and currents. Basic principle operation of movingiron instruments 61. The moving iron instrument uses the stationary coil as an electromagnet. It consists of permanent horseshoe magnets, coil, soft iron core, pivoted spring, nonmetallic frame, scale, and pointer. In addition to above instruments, we have wattmeters, power factor meters, frequency meters etc. The working principle of pmmc instruments are same as that of darsonaval type of galvanometer, difference being that a direct reading instrument is provided with pointer and scale. It would have a torque in one direction during one half of the cycle and an equal effect in. 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. Apr 20, 2018 working principle of moving iron instruments. Nevertheless, by making the fixed iron curved and tapering as shown in fig.
The current to be measured is passed through the coil, coil produced the magnetic field. In the attraction moving iron instrument a specially shaped piece of soft iron with a pointer attached is pivoted near to the open end of a short solenoid fig. Before going have a comparison between gravity control and spring control let us have a look at why we need controlling torque in a measurement instrument. Moving iron instruments are generally used to measure alternating voltages and currents. Voltmeters types of voltmeters with brief explanation. Moving iron instruments construction and basic principle operation.
Comparison of gravity control and spring control gravity control or spring control both are comes under the category of controlling torques of an electrical measurement instrument. There are four basic types of temperature measuring devices, each of which uses a different principle. The moving iron instruments use the stationary coil of copper or aluminium wire which. Electrodynamometer type instruments construction and. Planer machine parts, types, working principle with pdf. What is the difference between movingiron and movingcoil instruments. A moving coil instrument operates on the motor principle. Basic principle operation of moving iron instruments 61. Working principle of moving iron instruments electrical. Working principle of electrostatic type instruments. 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. Working principle and construction of pmmc polytechnic hub. 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.
Broadly, the analog instruments and for that matter digital instruments may be classified according to the quantity they measure. Jul 25, 2018 this instrument is one of the most primitive forms of measuring and relay instrument. Electromagnetic instruments are divided into simple moving iron, dynamo meter type and induction types of instruments. Permanent magnet moving coil or pmmc instrument definition. Movingiron instruments physics homework help, physics. Moving iron instruments attraction and repulsion type. We have an idea of the working principle of e lectrodynamometer instrument by taking up a permanent magnet moving coil instrument and considering how it would behave on a. Electrodynamometer type instruments construction and operation.
It operates on the principle that the torque is exerted on the moving coil placed in the field of the permanent magnet. Friends is video me ham moving iron instrument ke bare me discuss kar rahe hai, is video me apko moving iron instrument ke working principle, construction, advantage and disadvantages ke bare me. The magnetic field induces by the electromagnet whose strength depends. Pdf eec 126 instrumentation theory farouq osuolale. The electromagnet is the temporary magnet whose magnetic field strength increases or decreases with the magnitude of the current passes through it. Due to square low response, the scale of the moving iron instrument is nonuniform. Moving iron instrument working principle, construction. Used in ammeters, voltmeters, wattmeters, integrating meters etc. 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. Mar 16, 2018 pmmc stands for permanent magnet moving coil. Alternating current instruments ac page 45 moving iron instruments page 45 moving coil instruments with rectifier page 49 volt ammeter with switch page 4 maximun demand indicators page 415 triple quadruple instruments page 417 power power factor meter page 421 phase sequence indicators page 428 frequency instruments page 429. Movingiron instruments are generally used to measure alternating voltages and currents.
The moving system of the instrument is attached to the soft iron piece and the operating current is passed through a coil placed near it. Construction of attraction type moving iron instruments. A planer machine is very large and massive compared to a shaper machine. To this iron a pointer is attached so that it may deflect along with the moving iron over a graduated scale.
The operating magnetic field in moving iron instrument is very weak and. All of them infer temperature by sensing some change in a physical characteristic. General theory permanent magnet moving coil pmmc instruments 57. Analog instruments classification of analog instruments. Generally, an ebook can be downloaded in five minutes or less. Moving iron instruments principle and operation repulsion type. A hollow circular coil is used and one of the iron pieces is attached inside the hollow coil. If the flux density b is made constant by using permanent magnets and the conductor is a fixed length say, a coil then the force will depend only on the current. If two coils are connected such that, current proportional to the load voltage, flows through one coil and current proportional to the load current, flows through another coil, the meter can be calibrated directly in watts. Permanent magnet moving coil instruments pmmc the permanent magnet moving coil instruments are most accurate type for direct current measurements.
Moving iron instruments principle, operation and type, theory. Another type of instrument that is usually classed with the attractive types of instrument is shown in fig. The most widely used movingiron instruments are switchboard instruments of classes 1. 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. 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. Com is an online magazine for electrical engineers including machines,power systems,electronics and interview questions. Inside the coil, there are two soft iron pieces rods or vanes placed parallel to each other and along the axis, of the coil.
The instrument can be constructed to measure current and voltage to an accuracy needed in most engineering works and still be ch. I instrument the most common ammeter and voltmeter for laboratory or switch board use at power frequency are the moving iron instruments. Home advantages and disadvantages of movingiron instruments. It intended to produce plane and flat surfaces by a singlepoint cutting tool. When a conductor carrying current is placed in a magnetic field, a force f is exerted on the conductor, given by f bil. Permanent magnet moving coil or pmmc instruments are the most accurate type for the measurement of dc current or voltage. Rx is the unknown resistor to be measured, r2 is variable adjusted resistance so that the pointer read zero at short circuit test. In moving iron instruments, a plate or van of soft iron or of high permeability steel forms the moving element of the system. It consists of permanent horseshoe magnets, coil, soft iron. Feb 15, 2012 moving iron instruments moving iron instruments are the most common instruments used for measurements of electrical quantities.
It is an instrument for detecting and measuring electric current. Seventh lecture moving coil instruments 8 b series ohmmeter. It can be designed to step up or step down voltages and works on the magnetic induction principle. Still mi instruments are cheap as compared to any other type of a. The scale of series ohmmeter is nonlinear with zero at the right and infinity at extreme left. Moving iron instrument working principle, construction, advantage. The instrument in which the moving iron is used for measuring the flow of current or voltage is known as the moving iron instrument. Jul 25, 2018 working principle of electrostatic type instruments. Moving iron instruments moving iron instruments are the most common instruments used for measurements of electrical quantities. Advantages and disadvantages of movingiron instruments.
Ammeters, voltmeters are some of the examples of mi instruments. Click here to download the pdf of this topic moving iron instruments. As the name suggests the electrostatic type instrument use static electrical field to produce the deflecting torque. Hi friends, in this article, i am discussing about moving iron instruments working principle and other necessary related information. 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.
Hence moving iron instruments can be used for both a. Again moving iron classified as attraction and repulsion types of instruments. Pmmc instrument working principle permanent magnet moving coil. Rotation is opposed by a hairspring that produces the restoring torque. The basic construction of attraction type moving iron instrument is illustrated bellow. Ammeter working principle and types of ammeter ammeter. Movingiron measuring mechanisms are also used in ratio meters. Moving iron instruments principle, operation and type, theory of. A permanent magnet is used to produce magnetic flux and a coil that carries the current to be measured moves in this field. Dynamometer type wattmeter construction and working principle. The instrument consists of two high intensity, high coercive force magnets or a big ushape magnet based on design.
Principles and methods of temperature measurement course content temperature can be measured via a diverse array of sensors. They are used as wattmeters,varmeters and with some modification as power factor meters and frequency meters. Used in ac ammeters, voltmeters, watt meters and integrating meters. Working principle of moving iron instruments electrical concepts. The action of these instruments is based on the motoring principle. A transformer has no moving parts and is a completely. 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. It consists of a fixed cylindrical hollow coil which carries the operating current. While moving iron instruments are used in ac circuits.
In case of aminstruments with doubled overload range the overload range corresponds to approximately 20 % of the full scale length. Moving iron instruments having scales that are nonlinear and somewhat crowded in the lower range of calibration. Permanent magnet moving coil instrument or pmmc instrument the current i is shown which breaks into two components at the point the two components are is and before i. Download ebook by learn eee friends is video me ham moving iron instrument ke bare me. The various effects used are listed in the table present in the middle of this article. Figure below shows a simple moving iron instrument. Moving iron instruments principle, operation and type. In the attraction moving iron instrument a specially shaped piece of soft iron with a pointer attached is pivoted near to the open end of a. In this also consists of soft iron which is of movable and fixed coils. Moving iron instrument working operation electrical edition. Permanent magnet moving coil mechanism pmmc mathematical. 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.