Synchronous reluctance motors:

The operating principle of the fundamental reluctance motor is switched reluctance motors in the section.
The so-called "synchronous" reluctance motor has been designed to run on alternating current frequency hands and it uses stator windings similar to those distributed to those in cage induction motors. But the salient pole rotor has a variable reluctance magnetic circuit in the engine to create what dependent on the angular position of the rotor. These salient poles can be obtained by milling grooves along the axial length of a cage. See figure below.

Features:

The synchronous reluctance motor off not by itself, without the cage. During the term until it is like an induction motor goal, as it assumes approaches synchronous speed, the reluctance torque and locks in the synchronous speed of the engine.
Applications Used in regulated applications where speed control is required success as metering and industrial process equipment.

Hysteresis Motor:
The hysteresis synchronous motor consists of a wound stator produce a rotating field and a rotor in the form of a cylindrical casing made with all the bars of hard steel with relatively high magnetic hysteresis.
Upon starting, the combined effects of eddy currents caused in the steel induction motor action and residual magnetism in the steel causes the magnetic poles follow the rotating field, as well as causing the engine speed to build. Since the engine is behaving synchronous speed, the magnetic effect of the crossbar approaches like a permanent magnet causes the motor to the synchronous speed lock. The result is that the torque is approximately constant at all speeds.

Features Simple design:
Starts as an induction motor and locks in a synchronous motor.
With the rotor produces a smooth homogeneous material, the noise and vibration is naturally low. Since there are no pages or pole saliency, is the magnetic permeability of the permanent way, o that the magnetic pulses, which are the main cause of noise in the salient pole type.
Applications:

Their efficiency is low and limited applications for small power ratings.
Used extensively in tape recorders and clocks.
Meanwhile, largely replaced by permanent magnet motors.

Universal Motors:

An AC motor, which used to feed separately excited rotor windings on a rocker to the current rotor coils behave in the same way as a brushed DC motor, and may indeed be a universal motor having to supply either AC or DC source be used.
In contrast to induction and synchronous motors, the speed of universal motors is not limited by the electrical grid frequency and can easily more than one revolution per cycle. This makes them useful for appliances such as blenders, vacuum cleaners and hairdryers need What kind of high-speed operation. Speeds of up to 30,000 rpm are possible to the current carrying capacity is determined by the commutator and brushes, which limits their use on low-power applications in excess of 1 kW or less restricted to.