Why the terminal voltage of DC shunt generator decreases with increase of load current?

Direct-Current Machines For all d.c. shunt generators, the terminal voltage decreases as the machine is loaded for the following reasons: 1. The e.m.f. generated is reduced due to the effect of armature reaction which causes magnetic saturation at one of the pole tips and hence a reduction in the flux per pole.

What happens if the load current increases in case of DC motor *?

In case of DC shunt motor, the flux per pole is considered to be constant, torque increases with the increase of load current. If the load current increases then the armature current also be increased and the speed slightly falls due to increase in voltage drop in armature.

When there is a variation of load resistance which of the following DC generator can not deliver power at constant voltage?

Variation in load resistance causes the terminal voltage to vary. The terminal voltage will start falling, at saturation armature reaction effect becomes pronounced at large load current. Hence, series generators are not used for delivering power at a constant voltage.

Why terminal voltage decreases with the increase of load?

Why does the terminal voltage decrease and current increase? – Quora. In any circuit being powered by a small battery, if the load warms up and begins to decrease in resistance, it will cause the current to increase and because of the internal resistance of the battery, the voltage will decrease.

Is the terminal voltage of DC shunt generator on load same as its induced voltage why?

An external characteristic curve shows the relation between terminal voltage (V) and the load current (IL). Terminal voltage V is less than the generated emf Eg due to voltage drop in the armature circuit. Therefore, external characteristic curve lies below the internal characteristic curve.

When the load increases the speed decreases in DC shunt motor This is due to?

As the load increases, to maintain the voltage at a constant value, current decreases, due to which the strength of magnetic field produced by the Internal winding of DC motor decreases. This results in a decreased interaction of the two magnetic fields and thus decrease in speed of motor.

Why should the resistance of shunt field winding be high?

Hence as the current through series field winding is high, in order to keep voltage drop across it to a small value, its resistance is very low. On the other hand, the shunt field winding is directly connected across the rated supply voltage hence to limit current through it, resistance is very high.

Why is it desirable to have high shunt field resistance?

Adding resistance in series with the shunt field will reduce the field flux (strength). Less field flux will result in less counter emf (voltage) being produced at a given speed of the armature so the armature will tend to draw more current if the armature supply voltage is fixed.

What happens when load resistance of a shunt wound DC generator decreases?

When the load resistance of a shunt wound DC generator is decreased, then load current of the generator increased as shown in above figure. But the load current can be increased to a certain limit with (upto point C) the decrease of load resistance. Beyond this point, it shows a reversal in the characteristic.

What are the external and internal characteristics of a DC shunt generator?

The external characteristics are known by drawing a graph between the terminal voltage and the load current. The internal characteristics are known by drawing a graph between induced emf and the load current. The load test conducted on a dc shunt generator is shown in the figure below.

Why is a shunt generator called a constant voltage generator?

Thus the drop I a R a increases and terminal voltage V t = E – I a R a decreases. But the value of armature resistance is very small, the drop in terminal voltage as I L changes from no load to full load is very small. This is shown in the Fig. 3. Hence d.c. shunt generator is called constant voltage generator.

Why is the slope angle of a shunt DC generator constant?

Because in shunt dc generator the armature terminal voltage appears across the shunt field winding. Hence, this armature voltage divided by the corresponding field current is nothing but the shunt field resistance. Now if we slowly increase the resistance of the field coil, the slope angle of the straight line increases accordingly.

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