Machine Parts

  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?      Protecting Coating Shop   

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.               

Justify the statement: Stability of operation is an important factor in the parallel operation of generators. Shunt generators share the load proportionately. Should anything to occur to upset this proportionate division of load, it would be desirable for the generators to restore automatically the division of load. Assuming that the speed governor of one of the motors driving the generators is such that it will not hold the speed constant and because of this condition the speed of generator 2 will increase. The increase in speed will produce a large r induced voltage in generator 2,which in turn will cause generator 2 to deliver more load. Of course ,if generator 2 delivers more of the load, generator 1 delivers less. This larger load upon generator 2 will cause more current to flow in the armature of generator 2,producing a larger I a R a drop, a larger drop due to armature reaction, and a larger reduction in armature current, all of which tends to oppose the increas

With two generators connected in parallel, adjustments can be made for one generator to deliver all or any part of the load. If the resistance of the field rheostat of a generator is lowered, the resulting increase in field current will cause the generated voltage to increase. This increase in generated voltage causes the load delivered by the generator to increase. Naturally if one generator takes more load, the other generator drops some load. Hence by adjusting the field rheostats of the generators, the load can be shifted from one generator to the other or divided in any proportion desired.