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Transcript of Electrodynamometer
The electrodynamometer is a transfer instrument.
It can be used in measuring both DC and AC measurement.
It can measure not only power line frequency but also can measure audio frequency range. History of Electrodynamomete The basic principle of electrodynamometer was laid out in an 1848 paper by Wilhelm Weber (1804-1891)
When the same current passes through two concentric coils placed at right angles to each other, the resulting torque depends on the square of the current. PHYSICAL CONSTRUCTION OF DYNAMOMETER
The moving coil is mounted on an aluminum spindle. It consists of pointer and counter weight. The suspension used in case of high accuracy desired. Pointer Produce the necessary field that required by the pointer to deflect from the initial place. Fixed Coil Same as the fixed coil unless the facts that is will rotating during the flowing of the current that flow inside it. Moving Coil Hairspring Controlling torque is provided by the hairspring. The hairspring is the element that will push the pointer to its Origin. The field that produced by the instrument are consider as very weak. Sometimes, the weakness can affected by earth’s magnetic field and cause the reading affected. So, the shielding is done to protect it from stray magnetic field. Shielding How Electrodynamometer Works? How Electrodynamometer Works? Left hand rule explained when the current carrying conductor wires are placed in a magnetic field, it will pushed away
This discovery is the fundamental of electrodynamometer pointer deflects The working principle of electrodynamometer is as same as motor rotation but it is limited to a certain angle which is about 120 degrees only rather than motor that can rotate freely.
The pointer rotate/deflect together with coil, it will stop its deflection when the force of the electromagnet equal to the force of the hairspring.
The meter is a transfer instrument, it can work in both AC and DC without any problem. CONNECTION OF ELECTRODYNAMOMETER Electrodynamometer as Ammeter Electrodynamometer as Voltmeter Electrodynamometer as Wattmeter 1. Electrodynamometer of Wattmeter
- Measurement of Power
2. Electrodynamometer of Ammeter
- Measurement of Current
3. Electrodynamometer of Voltmeter
-Measurement of Voltage APPLICATIONS OF
When the electrodynamometer is used as an ammeter, a special type of construction must be used.
This is because the large currents that flow through the meter cannot be carried through the moving coils.
In the ammeter circuit in view B of stationary coils a and b are wound of heavier wire to carry up to 5.0 amperes.
An inductive shunt (XL) is wired in parallel with the moving coils and permits only a small part of the total current to flow through the moving coil.
The current flowing through the moving coil is directly proportional to the total current flowing through the instrument. Electrodynamometer Ammeter Electric power is measured by means of a wattmeter.
This instrument is of the electrodynamometer type.
It consists of a pair of fixed coils, known as current coils, and a moving coil, called the voltage (potential) coil.
The fixed current coils are wound with a few turns of a relatively large conductor. Electrodynamometer wattmeter Electrodynamometer Voltmeter - When an electrodynamometer is used as a voltmeter, current required is not
more than 0.1 ampere.
- This amount of current can be handled easily by the spiral springs.
- Fixed coils a and b are wound of fine wire since the current flow through them
will not exceed 0.1 ampere.
- They are connected directly in series with movable coil c and the series
current-limiting resistor. Advantages and Disadvantages Since the coil are air cored, the instruments are free from hysteresis and eddy current losses.
It is free from hysteresis errors. Advantage
It have non-uniform scale
It is sensitive to overloads and any mechanical impacts. Therefore, a safety precaution must be taken care while handling the electrodynamometer.
The operating current are large due to the facts that it need a large amount of current to create an electromagnetic field. Disadvantage Thanks You...