n DC ……machines the resistor of the field winding is high whereas its value in DC……..  machine is low. *Shunt-SeriesSeries- ShuntSeries- SeriesShunt – Shunt

It appears that you're asking about the differences between shunt and series DC machines, particularly in relation to the resistance of the field winding. Here's a detailed explanation:

1. Field Winding Configurations:

   • Shunt DC Machines: In a shunt DC machine, the field winding is connected in parallel with the armature winding. This configuration results in a high resistance for the field winding. The shunt field winding typically has many turns of wire with a small diameter, which increases its resistance. This is advantageous as it allows the field current to be relatively constant, providing better voltage regulation.

   • Series DC Machines: In a series DC machine, the field winding is connected in series with the armature. This means that the same current flowing through the armature also passes through the field winding. As a result, the resistance of the field winding in a series machine is low compared to that of a shunt machine. Series windings usually consist of fewer turns of thicker wire. This design is beneficial for applications requiring high starting torque, as the field strength increases with load current.

2. Applications and Performance:

   • Shunt DC machines are typically used in cases where constant speed is required, such as in fans and pumps.
   • Series DC machines are used in applications demanding high starting torque, like electric traction and cranes.

3. Voltage and Current Relationship:

   • In a shunt machine, since the field current is independent of the load current, the machine remains more stable under varying load conditions.
   • A series machine experiences fluctuations in field strength with load variations, affecting overall performance.

In summary, the key difference lies in the configuration of the field windings, which influences the machine's resistance and overall performance under different operating conditions.