Which of the following single-phase motors is suitable for timing and control purposes?
Right Answer is:
Reluctance Motor is suitable for timing and control purposes.
Single-phase induction motors built with a variable air gap reluctance with no DC supply on the rotor are called reluctance motors. Such motors start like induction motors but are pulled into synchronous speed because of the variation in air gap reluctance. This pull-in force on such motors is based on the magnetic reluctance principle.
- The single-phase reluctance motor can either be of split-phase type or capacitor-type.
- A single-phase supply is therefore provided to the main and auxiliary winding spaced 90° apart on the stator.
- The stator produces the revolving field. The rotor of any uniformly distributed single-phase induction motor is modified or altered as shown in Figure, where it is shown that some iron portions of the rotor have been chipped or cut away so as to produce salient rotor – poles.
- In this way, the reluctance of the air-gap flux path will be greater where there are no conductors embedded in slots.
- Thus the rotor flux offers variable magnetic reluctance to the stator flux, as the reluctance of the air-gap flux path varies with the position of the rotor. The salient poles have lower-reluctance air gaps.
Application of Reluctance Motor
These motors have a constant speed, rugged construction, do not need DC excitation, and need minimum maintenance. The constant speed characteristics of the reluctance motor for application such as
- Analog electric meters.
- Some washing machine designs.
- Control rod drive mechanisms of nuclear reactors.
- Hard disk drive motor.
- Signaling device
- Recording Instrument
- Timing and control