Analog Instrument basic of electricity.pptx

Basic of analog in electrical engineering used in day to today life and application in electrical system .Basic of analog in electrical engineering used in day to today life and application in electrical system Basic of analog in electrical engineering used in day to today life and application in electrical system

1. K.S.RANGASAMY COLLEGE OF TECHNOLOGY (Autonomous) Tiruchengode – 637 215, Namakkal (Dt.), Tamil Nadu. Department of Electrical and Electronics Engineering Course Name: Basic Electrical and Electronics Engineering Presentation by S.Jaividhya Assistant Professor / EEE E-Mail ID: [email protected] Moving Iron Instruments 1 1/30/2024

2. Moving Iron Instruments Introduction The movable system consists of one or more pieces of specially-shaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil. Used to measure both AC and DC quantity Two types of moving-iron instruments Repulsion (or double iron) type Attraction (or single-iron) type . 2 1/30/2024

3. Moving Iron Instruments Attraction type Moving Iron Instruments Principle A soft iron piece gets magnetized when it is brought into a magnetic field. The same phenomenon happens when the soft iron piece is brought near either of the ends of a coil carrying current. The iron piece is attracted towards that portion where the magnetic flux density is more. This movement of soft iron piece is used to measure the current or voltage which produces the magnetic field. 3 1/30/2024

4. Moving Iron Instruments Attraction type Moving Iron Instruments Deflecting torque is produced by the current or the voltage to be measured. It is proportional to the square of the voltage or current. Hence, the instrument can be used to measure DC or AC Scale is non- uniform Control torque : Spring or gravity Damping : Air friction damping 4 1/30/2024

5. Moving Iron Instruments Repulsion type Moving Iron Instruments Two iron piece kept with close proximity in a magnetic field get magnetized to the same polarity. Hence, a repulsive force is produced. If one of the two piece is made movable, the repulsive force will act on it and move it on to one side. This movement is used to measure the current or voltage which produces the magnetic field 5 1/30/2024

6. Moving Iron Instruments Repulsion type Moving Iron Instruments When the current to be measured is passed through the fixed coil it sets up its own magnetic field which magnetizes the two rods similarly the adjacent points on the lengths of the rods will have the same magnetic polarity. Hence, they repel each other with the result that the pointer is deflected against the controlling torque of a spring or gravity. The force of repulsion is approximately proportional to the square of the current passing through the coil Whatever be the direction of current in the coil, the two irons are always similarly magnetised 6 1/30/2024

7. Moving Iron Instruments Torque Equation 7 1/30/2024

8. Moving Iron Instruments Advantages & Disadvantages Advantages 1. The instruments are suitable for use in AC and DC circuits. 2. The instruments are robust, owing to the simple construction of the moving parts. 3. The stationary parts of the instruments are also simple. 4. Instrument is low cost compared to moving coil instrument. 5. Torque/weight ratio is high, thus less frictional error. Disadvantages 1. Scale is not uniform. Cramped at lower end. 2. Serious errors due to hysterisis , frequency changes, stray magnetic field. 3. Increase in temperature, increases resistance of coil, decreases stiffness of springs . 8 1/30/2024

9. Moving Iron Instruments Errors in Moving Iron Instruments 1. Hysterisis error-due to the different value of flux density for the same current for ascending and descending values. 2. Temperature error-due to the effect of temperature on the temperature co-efficient of the spring-cause self heating of coil –can be avoided by using Manganin material. 3. Stray magnetic fields-due to weak magnetic field. 4. Frequency error-due to change in frequency. 5. Eddy current error-due to the production of eddy current in the iron parts of the instrument-affects change in deflection. 9 1/30/2024

10. Thanking You 10 1/30/2024