When not connected to a load resistance, generators will generate voltage roughly proportional to shaft speed. With precise construction and design, generators can be built to produce very precise voltages for certain ranges of shaft speeds, thus making them well-suited as measurement devices for shaft speed in mechanical equipment. A generator specially designed and constructed for this use is called a tachometer or tachogenerator. Often, the word “tach” (pronounced “tack”) is used rather than the whole word.
It states that whenever there is a relative motion between the magnetic field and a conductor , then the voltage is generated in that conductor. Characteristic requirements of tachogenerator: ?Accuracy: The input to the tachogenerator is speed and the output is electrical voltage. The voltage should be measured correctly so that it can indicate the speed accurately ? Resolution: The analogue voltage measuring device should have division and subdivision of scale small enough, calibrated to indicate the smallest variation of speed. ?Linearity: If the relationship between voltage and speed is linear the scale will be linear.
It may be easy to read in case of fraction of subdivision. ?Temperature effect: Armature and field winding resistances are affected by temperature depending upon temperature resistance coefficients. The magnetic property of the core is also temperature dependent . If temperature variations are excessive physical expansion coefficient may affect the dimentions. ?System voltage: If the system voltage use for excitation is fluctuating , the output relation may be affected. ?Residual error: In case of electromagnetic type field for DC tachogenerator the residual flux may give error.
The Essay on The Effect Of Temperature On The Rate Of Diffusion
Molecules undergo constant motion and move in regions with a higher concentration to a lower concentration and this process is called diffusion. It is where particles make numerous collisions with one another and so with the partition. This movement of the particles causes them to be equally and uniformly distributed throughout, (De et. al, 2010). It can occur in any state of matter. The ...
In case of AC tachogenerator statically –induced voltage by transformer action and harmonics may lead to residual error at zero speed. ?Radio Noise: The moving contacts at brushes, commutators , arcing and ripple create radio frequency disturbing signals . ?Phase Shift: In case of AC tachogenerator the resistance, reactance and impedence create phase difference. ?Reliability: Reliability of any system component is essential. ?Torque : Tachogenerator are like generators running without load but the rotating system has some mass, inertia and friction .
One of the two stator windings called primary winding is connected to the rated voltage at rated frequency . It provides necessary AC excitation. Due to this excitation alternating flux Om of the same frequency same as that of supply is established in the air gap. The rotor is driven by its shaft coupled to the machine whose speed is to be measured. The relative motion between rotor and stationary but alternating stator flux Om develops dynamically induced AC voltage in the rotor which is proportional to the speed.
At the same time transformer action induces statically induced EMF in the rotor. The dynamically induced voltage by flux Om establish current in rotor. Rotor current establish flux Oc perpendicular to main flux as shown in figure. The cross field flux Oc links with out put winding on the stator and develops voltage by transformer action. The voltage in the output winding is proportional to the dynamically induced EMF in rotor, which is proportional to angular speed of the rotor. So finally voltage across output winding is proportional to the rotor speed imparted by the shaft speed to be measured .
The Essay on Magnetic Field and Average Voltage
Purpose: To prove Faraday’s Law of Induction using an oscillating wand which swings through a magnetic field. In addition, we studied the conversion of mechanical energy to electrical energy. Questions: 1. What are the possible errors in this experiment? There are a variety of sources of error which may have affected the results of this experiment. There could have been an error in the setup ...
