.The induction motor is the most popular type of AC motor because of its simplicity and ease of operation.An induction motor does not have a separate field circuit:instead,it depends on transformer action to induce voltages and currents in its field circuit.In fact,an induction motor is basically a rotating transformer.Its equivalent circuit is similar to that of a transformer,except for the effects of varying speed. DC machinery fundamentals DC machines are generators that convert mechanical energy to DC electric energy and motors that convert DC electric energy to mechanical energy.Most DC machines are like AC machines in that they have AC voltages and currents within them-DC machines have a DC output only because a mechanism exists that converts the interal AC voltages to DC voltages at their terminals. Since this mechanism is called commutator,DC machinery is also known as commutating machinery. DC motors and generators DC motors are DC machines used as motors,and DC generators are DC machines used as generators.The same physical machine can operate as eithe a motor or a generator-it is simply a question of the direction of the power flow through it. There are several types of DC motors,differing in the manner in which their field fluxes are derived.These types of motors are separately excited,self- excited and permanent magnet.The manner in which the flux is derived affects the way it varies with the load,which in turn affects the motor's overall torque- speed characteristic. DC generators are DC machines used as generators.There are several different types of DC generators,differing in the manner in which their field fluxes are Unit 2 Electric Machinery and Electrical Equipment 27 9 The induction motor is the most popular type of AC motor because of its simplicity and ease of operation. An induction motor does not have a separate field circuit; instead, it depends on transformer action to induce voltages and currents in its field circuit. In fact, an induction motor is basically a rotating transformer. Its equivalent circuit is sim ar to that of a transformer, except for the effects of varying speed. DC machinery fundamentals 10 DC machines are generators that convert mechanical energy tone electric energy and motors that convert DC electric energy to mechanical energy. Most 1 DC machines are lik~ AC mac nes in that they have AC voltages and currents wit them - DC machines have a DC output only because a mechanism exists that converts the internal AC voltages to DC voltages at their terminals. Since this mechanism is called commutator, DC machinery is also known as commutating machinery. DC motors and generators 11 DC motors are DC machines used as motors, and DC generators are DC machines used as generators. The same physical mac can operate as either a motor or a generator - it is simply a question of the ection of the power flow through it. 12 There are several types of DC motors, diffe in the manner in which their field fluxes are derived. These types of motors are separately excited, self￾excited and pem nent magnet. The manner in which the flux is derived affects the way it varies with the load, which in turn affects the motor's overall torque￾speed characteristic. 13 DC generators are DC machines used as generators. There are several different types of DC generators, differing in the manner in hich their field fluxes are Unit 2 Electric Machinery and Electrical Equipment 27