AC MotorsAC MOTOR TYPESAC MOTOR TYPESVarious types of AC motors are used for specific applications. By matching thetype of motor to the appropriate application, increased equipment performancecan be obtained.EO 1.5 DESCRIBE how torque is produced in a single-phaseAC motor.EO 1.6 EXPLAIN why an AC synchronous motor does not havestarting torque.EO 1.7 DESCRIBE how an AC synchronous motor is started.EO 1.8 DESCRIBE the effects of over and under-exciting an ACsynchronous motor.EO 1.9 STATE the applications of the following types of ACmotors:a. Inductionb. Single-phasec. SynchronousInductionMotorPrevious explanations of the operation of an AC motor dealt with induction motors. Theinduction motor is the most commonly used AC motor in industrial applications because of itssimplicity, rugged construction, and relatively low manufacturing costs. The reason that theinduction motor has these characteristics is because the rotor is a self-contained unit, with noexternal connections. This type of motor derives its name from the fact that AC currents areinduced into the rotor by a rotating magnetic field.The induction motor rotor (Figure 5) is made of a laminated cylinder with slots in its surface.The windings in the slots are one of two types. The most commonly used is the "squirrel-cage"rotor. This rotor is made of heavy copper bars that are connected at each end by a metal ringmade of copper or brass. No insulation is required between the core and the bars because of thelow voltages induced into the rotor bars. The size of the air gap between the rotor bars andstator windings necessary to obtain the maximum field strength is small.Rev. 0 Page 9 ES-12
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