Machine Parts

When a current is flow through the armature conductor, a magnetic field is set up around the conductor. The interaction between this magnetic field flux and main field flux is called armature reaction.              The armature magnetic field has two effects- ·          If demagnetizer or weakens the main field flux. For the weakness of the main field flux the generated voltage is reduced. ·          It’s cross magnetizing component produces spark at the brushes due to the resultant field flux. Which is not in the same direction as the original main field flux but runs from the tip of one of the poles across the armature to the tip of the other pole.   Monocrystalline solar cell used in Smartphone                       Mechanism of Solar Collector for Flat Plate                            Why a self excited shunt generator will not build up voltage?     How can the voltage, current and power ratings of a generator be adjusted?

The circuit shows in figure 1 is used to duplicate the required flux and speed for any specific load. The rheostat in series with the armature is adjusted until the voltmeter reads the same as the induced voltage at the specific load (generated voltage if the dynamo is a generator, counter emf if the dynamo is a motor. Since the I a R a drop of the dynamo as connected is very small, it can be neglected and the voltage across the armature is assumed to be the counter emf. The field rheostat is now adjusted to obtain the same speed at the specific load condition. The voltage induced in a dynamo is given by the equation E=KΦS. Inasmuch as the induced voltage as well as the speed have now be duplicated, it is apparent from the formula that the flux must now be the same as the flux at the load condition. Having duplicated the flux and the speed, the stray power is now determined by subtracting the copper loss from the power input to the armature.               

Phasing of a transformer :  Two dimensional vector is known as phasor.As the vector diagram of a transformer is drawn in phasor form and this is called the phasing of transformer. When load is applied to the secondary terminal the current that flows through the secondary terminal opposite to the primary current from lenz’s law.So flux is reduced,causes the induced emf in the primary winding is also reduced and therefore more current flows in the primary winding.This increased primary current will cause the flux to increase its original value.When more load current flow through secondary,the process is repeated. Phasor diagram with load : When load is connected the load current I 2 is   lagging E 2 .I 1 ̕   is the current that flows in the primary winding to balance the demagnetizing effect of I 2 .Since the flux remains constant I o   must be the same current that energizes the transformer at no load I 1 the actual current that   flows in the p

The process to determine the transformer constants referred to the low voltage side if only one set of high voltage measurement is taken , is to short circuit the low voltage side. Then the watt meter W, a voltage V and an ammeter A are connected in the high voltage side i.e. primary winding. A low voltage usually 5% to 10% of the rated supply voltage is applied to the primary and is continuously increase till full load current will flow both in primary and secondary winding.      As 5% of rated voltage is necessary to overcome the impedance which is the only limiting component   of current flow through each winding. The impedance is formed by the resistance and reactance of two windings.      Now the total impedance of the transformer is given by Z T =V 1 /I 1 . Where V1 is the applied voltage and I1 is the rated current. Since flux is directly proportional to voltage, the mutual flux in the transformer under the short circuit test is very small. So,the iron or c