A shunt generator is a device that produces electric power output from an armature winding using a field winding that taps from the same electric power output. The field winding is the counterpart of early permanent magnets that provided the magnetic fields that were cut by the armature windings, producing the generator electrical output. Shunt generators come in various connection configurations such as the long shunt and the short shunt. The shunt field in the long shunt is parallel with the series combination of the armature and the series field, while in the short shunt, the parallel combination of the armature and shunt field is in line with the series field.
Shunt generators make use of the same generated electrical energy to sustain the electrical generation process. From standstill, the shunt generator only has a residual magnetic field that will produce a very small amount of electrical energy in the first few fractions of a second. The small electrical energy produced will build up the magnetic field, which results in bigger electrical energy output. Meanwhile, in the same shunt generator, the field winding may be in parallel with the electrical output, and so the voltage across the field winding builds up as the electrical output builds up.
In a steadily running shunt generator, the mechanical energy input is the final requirement to sustain electrical power generation. The mechanical torque that turns the armature windings is being converted into electrical energy. As the electrical currents are generated, more torque is needed up to a point where the load power is maintained at a given mechanical input. Any increase or decrease in load power will reflect as increase or decrease in mechanical loading, given there is a voltage control circuit.
The simplest direct current generator may have a permanent magnet instead of a field winding. It should be noted that an electromagnet is required to produce a controllable magnetic field, which is the main energy source of the electromagnetic induction process involved, resulting in an electromagnet with a winding that is commonly referred to as the field winding. The field winding and the armature winding may be connected in various configurations. There may even be a series field winding along with a parallel field winding. The former and the latter are commonly referred to as series field and shunt field, respectively.
Electric motors work on reciprocal principles as that of generators. When electrical energy is fed into an electric motor, there is both rotor and field energy that interact to generate the needed mechanical output. The opposite process is electrical power generation where both residual magnetic field and mechanical torque eventually produce a stable electrical power output.