The rotor of the synchronous machine carries a field winding that is supplied with d.c. through two slip rings by a separate d.c. source. Synchronous Rotor construction is of two types, namely :
Salient (or projections) pole type.
Cylindrical type (or non-salient pole type)
In this type, salient poles are mounted on a large circular steel frame which is fixed to the shaft of the alternator.
The rotors of salient-pole rotor machines have concentrated winding on the poles and a nonuniform air gap.
Salient pole generators have a large number of poles. sometimes as many as 50, and operate at lower speeds.
The synchronous generators in hydroelectric power stations are of the salient pole type and are driven by water turbines.
The rotors are shorter axial length but have a large diameter.
A DC motor can be operated from a single-phase AC supply.
The direction of the torque produced by a DC machine is determined by the direction of current flow in the armature conductors and by the polarity of the field.
Torque is developed in a DC machine because the commutator arrangement permits the field and armature currents to remain in phase, thus producing torque in a constant direction.
A similar result can be obtained by using an AC supply, and by connecting the armature and field windings in series.
The amount of flux produced by the magnet indicates the strength of the magnet. The more the magnetizing force (MMF), the more is the flux produced. The more the opposition to the flux path (i.e., reluctance or magnetic resistance) less is the flux produced. This relationship is expressed as
Flux = MMF/ Reluctance
Reluctance is the opposition offered by the material in the flux path to the establishment of the flux. The reluctance in a magnetic circuit is similar to the resistance in an electric circuit. Reluctance is the inverse of permeance.
MMF = Flux/Permeance
Form factor: The ratio of r.m.s (or effective) value to average value is the form factor (Kf) of the Waveform. It has used in voltage generation and instrument correction factors.
Peak factor: The ratio of maximum value to the r.m.s value is the peak factor (Kp) of the waveform.
Form Factor × Peak Factor = (RMS Value / Average Value) * (Maximum Value / RMS Value) = Maximum Value / Average Value
In the exclusive OR gate (XOR gate) has two inputs
The ouput will be 1 when either input is 1 i.e X = 1 and Y = 1, but not when both the inputs are 1.
If both the input is zero i.e X = 0 and Y = 0, then the output is 0.