Presentation on dynamometer and type.pptx

It is for electric engineering students

1. GOVT . POLYTECHNIC KANGRA Submitted by: AYUSH [10] Elec. 4 th Semester 210710405013 Submitted to: Mr. Sandeep Bhardwaj

2. WHAT IS DYNAMOMETER TYPE WATTMETER AND ITS MERITS AND DEMERITS?

3. Contents : Introduction Diagram Construction Working Merits Demerits Errors

4. Dynamometer type wattmeter This is an indicating type instrument which is used to measure the power in an electric circuit and it is known as watt meter. This measures the watt or kilowatts. This is universally used for the measurement of d.c. and a.c. power. When it is used as watt meter , the fixed coils are connected in series with the load and carry the load current.

5. Construction : In Dynamometer Type Wattmeter has a fixed coil divided into two parts and it is connected in series with the load and carries the load current(I 1 ). The moving coil is connected across the load through a series multiplier resistance (R) and carries current (I 2 ) proportional to the load voltage. The fixed coils are connected in series with the load and carry the load current. The fixed coil is known as current coil and the moving coil is known as potential coil . The pointer is also attached with the moving coil.

6. When a current carrying moving coil is placed in the magnetic field produced by the current carrying fixed coil. A Force is exerted on the sides of coil of moving coil , thus deflection takes place and so the pointer moves over the scale. The pointer comes to rest at a position where controlling torque . The reversal of current reverse the current in current coil , both fixed coil and pressure coil so the direction of the deflecting torque remains unchanged. Hence such instruments can be used on d.c. as well as a.c. power. Working :

7. Merits : These instruments may be used both on A.C. and D.C. By careful designing , high accuracy can be obtained i.e. Instruments with errors as low as 0.1% to about 2% can be produced. These instruments have uniform scale. Ammeters up to 10 A and voltmeters up to 600 V can be constructed. These instructions are free from eddy currents losses.

8. Demerits : These instruments are expensive. The operating field being weak , the reading are affected by stay fields. The torque is small. They have a precision grade accuracy. These instruction are sensitive to overloads and mechanical impacts , therefore they must be handled with great care. These instructions have a low sensitivity due to a low torque to weight ratio.

9. Errors : Error due to the friction of moving system. Error due to the fact that springs are subjected to ageing. Error due to connection of potential coil circuit. Error due to Eddy currents. Error due to temperature rise thereby increasing resistance of the moving and fixed coils. Error due to mutual inductance effects. Error due to pressure coil capacitance.