Machine Parts

If the counter emf   becomes equal to the applied voltage, then current through the armature conductor will be zero and for this armature of motor will not rotate. Thus again the counter emf of the motor will be zero. So the counter emf can never be equal or greater than terminal voltage of a motor. Explain the universality of the statement that motor action is always accompanied by generator action or vice versa:  When armature of motor rotates in magnetic field, then the conductors cut flux and for this reason a voltage is induced across the armature. This is the motor action accompanied by the generator action. In the case of a generator, current flows through the conductors of the armature. When a current flowing conductor is placed in a magnetic field, it rotates. Thus it is the generator action accompanied by motor action. What are the detrimental effects of armature reaction on the performance of a dc machine?    Mecha...

  The use of shunt generator is somewhat restricted. It is used to supply power to equipment located within the immediate vicinity of the generator. Its use is not satisfactory for supplying power to remotely located points because not only does the terminal voltage of the generator drop as load increases, but there is also a voltage drop in the line. The greater the load the greater the greater the voltage drop in line. The combined effect of the reduction in generator voltage plus the line drop makes the shunt generator unsatisfactory for the transmission of power over long distances. Diverter resistor: A resistance shunting the series field of a compound generator to adjust the degree of compounding to produce a desired voltage regulation is called diverter resistor. 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.   ...