<P> An electric generator or electric motor consists of a rotor spinning in a magnetic field . The magnetic field may be produced by permanent magnets or by field coils . In the case of a machine with field coils , a current must flow in the coils to generate the field , otherwise no power is transferred to or from the rotor . The process of generating a magnetic field by means of an electric current is called excitation . </P>
<P> An electric generator or electric motor consists of a rotor spinning in a magnetic field . The magnetic field may be produced by permanent magnets or by field coils . In the case of a machine with field coils , a current must flow in the coils to generate the field , otherwise no power is transferred to or from the rotor . The process of generating a magnetic field by means of an electric current is called excitation . </P>
magnetic field in a dc generator is produced by
magnetic field in a dc generator is produced by
excitation
excitation