Electric DC machines, as indeed any other type of electric machine, can be used to either produce electric energy from the input mechanical energy, or to convert electric energy into output mechanical energy. These two possible operating regimes are called generation and motoring. | ENGNG2024 Electrical Engineering STEADY STATE OPERATION OF DC MACHINES 1. INTRODUCTION Electric DC machines as indeed any other type of electric machine can be used to either produce electric energy from the input mechanical energy or to convert electric energy into output mechanical energy. These two possible operating regimes are called generation and motoring. As already mentioned DC machines used to be in the past the major source of DC power. In order to produce electric power DC machines were operated as generators. Nowadays however use of DC generators is becoming more and more rare. DC power is obtained instead by means of power electronic converters. The remaining applications of DC machines are today restricted to motoring. In this operating regime a DC machine is operated as a DC motor it consumes DC power while delivering at its shaft mechanical power. The shaft drives a certain load that is characterised with the load torque. A DC machine consists of stationary part called stator and rotating part called rotor. Both stator and rotor are equipped with one winding. Stator winding is supplied from a DC voltage source and the role of this winding is to produce magnetic flux in the air gap of the machine. This flux is stationary in space. Rotor winding is again supplied from a DC voltage source for motoring DC supply is connected to the rotor winding through a special assembly that is composed of brushes and commutator. Brushes are stationary while commutator is fixed to the rotor and hence rotates together with the rotor. This assembly enables supply of electric power from stationary power supply to rotating winding on rotor. Principle of operation of this assembly is illustrated by means of Fig. 1. Rotor winding is shown in a very simplified manner as consisting of just one coil connected to two segments of the commutator. Motoring action is assumed and the current is therefore delivered to the rotor winding through the stationary brushes and rotating .
