Induction Motor and Faults
The chapter deals with general description of an induction motor followed by different faults. First, construction of induction motor has been discussed. Then a review of induction motor fault has been presented. Faults like rotor broken bar, mass unbalan
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Induction Motor and Faults
Abstract The chapter deals with general description of an induction motor followed by different faults. First, construction of induction motor has been discussed. Then a review of induction motor fault has been presented. Faults like rotor broken bar, mass unbalance, stator faults, single phasing, crawling, bearing faults, etc. are discussed along with causes and effects.
Keywords Bearing fault Broken rotor bar Construction Crawling Induction motor Mass unbalance Single phasing Stator fault
Chapter Outcome Aftercompletion of the chapter, readers will be able to gather knowledge and information regarding the following areas: • • • • • • • • • • •
Construction of induction motor Different classes of induction motor Different motor faults Statistics on motor fault Broken rotor bar Rotor mass unbalance Stator winding fault Single phasing Crawling Bearing fault Over/under voltage, overload.
2.1
Introduction
An induction motor comprises a magnetic circuit interlinking two electric circuits which are placed on the two main parts of the machine: (i) the stationary part called the stator and (ii) the rotating part called the rotor. Power is transferred from one © Springer Science+Business Media Singapore 2016 S. Karmakar et al., Induction Motor Fault Diagnosis, Power Systems, DOI 10.1007/978-981-10-0624-1_2
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2 Induction Motor and Faults
Fig. 2.1 An induction motor (dissected)
Fig. 2.2 Magnetic circuit of stator and rotor of an induction motor
part to the other by electromagnetic induction. For this induction machine is referred as an electromechanical energy conversion device which converts electrical energy into mechanical energy [1]. Rotor is supported on bearings at each end. Generally, both the stator and rotor consist of two circuits: (a) an electric circuit to carry current and normally made of insulated copper or insulated aluminum and (b) a magnetic circuit, shown in Fig. 2.2, to carry the magnetic flux made of laminated magnetic material normally steel (Fig. 2.1).
2.2 Construction
2.2
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Construction
(a) Stator The stator, shown in Fig. 2.3, is the outer stationary part of the motor. It consists of (i) the outer cylindrical frame, (ii) the magnetic path, and (iii) a set of insulated electrical windings. (i) The outer cylindrical frame: It is made either of cast iron or cast aluminum alloy or welded fabricated sheet steel. This includes normally feet for foot mounting of the motor or a flange for any other types of mounting of the motor. (ii) The magnetic path: It comprises a set of slotted high-grade alloy steel laminations supported into the outer cylindrical stator frame. The magnetic path is laminated to reduce eddy current losses and heating. (iii) A set of insulated electrical windings: For a 3-phase motor, the stator circuit has three sets of coils, one for each phase, which is separated by 120° and is excited by a three-phase supply. These coils are placed inside the slots of the laminated magnetic path. (b) Rotor It is the rotating part of
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