Electronic Control of AC Motors Efficient control of motors becomes critical where high precision, accuracy, reliability and faster response are of paramount importance. Electronic and digital controls are employed in such conditions. Classes of Electronic A.C. Drives AC motors, particularly, the squirrel-cage and wound-rotor induction motors as well as synchronous motors lend themselves well to […]
Electric Braking of Motors There are three types of electric braking as applicable to electric motors. In many cases, provision of an arrangement for stopping a motor and its driven load is as important as starting it. For example, a planing machine must be quickly stopped at the end of its stroke in order to
Standard Types of Squirrel Cage Motors Different types of 3-phase squirrel-cage motors have been standardized, according to their electric characteristics, into six types, designated as design A, B, C, D, E and F respectively. The original commercial squirrel-cage induction motors which were of shallow slot type are designated as class A. For this reason, Class
Linear motors move in a straight line with linear force and speed. Linear motion is needed in many types of systems, but linear motors aren’t commonly used by makers or professional engineers. That’s because these motors aren’t well-understood, there aren’t many manufacturers, and they’re expensive. For these reasons, designers frequently obtain linear motion by connecting
Development of Induction Motor Equivalent Circuit Physically, the construction of the wound-rotor induction motor has striking similarities with that of the 3-phase transformer, with the stator and rotor windings corresponding to the primary and secondary windings of a transformer. In the light of these similarities, it is not surprising that the induction motor equivalent circuit
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Influence of Rotor Current on Flux Up to now, all our discussion in previous articles has been based on the assumption that the rotating magnetic field remains constant, regardless of what happens on the rotor. We have seen how torque is developed, and that mechanical output power is produced. We have focused attention on the
Torque Production in Induction Motor In this article we begin with a brief description of rotor types, and introduce the notion of ‘slip’, before moving onto explore how the torque is produced, and investigate the variation of torque with speed. We will find that the behaviour of the rotor varies widely according to the slip,
Rotating Magnetic Field of Induction Motor Like the d.c. motor, the induction motor develops torque by the interaction of axial currents on the rotor and a radial magnetic field produced by the stator. But, whereas, in the d.c. motor the ‘work’ current has to be fed into the rotor by means of brushes and a
Inverter Fed Induction Motor Drives Induction motor can only run efficiently at low slips, i.e. close to the synchronous speed of the rotating field. The best method of speed control must therefore provide for continuous smooth variation of the synchronous speed, which in turn calls for variation of the supply frequency. This is achieved using
Speed Control of Induction Motor To operate efficiently an induction motor must run with a small slip. It follows that any efficient method of speed control must be based on varying the synchronous speed of the field, rather than the slip. The two factors that determine the speed of the field, are the supply frequency