[...]... performed by an electric motor And power determines how fast the work may be accomplished © Cengage Learning 2013 NEMA-rated electric motors is horsepower, and for IEC-rated motors is watts One horsepower is defined as performing 550 foot-pounds of work in one second, and the horsepower-to-watts conversion factor is 1 horsepower = 746 watts Figure  2-1 0  Graticule with out-of-phase waveforms showing... moving parts of the motor centered in the stator core, are also mounted to the motor housing Mounting Base The motor base for the motor pictured in Figure  2-1 is labeled on the lower left There are many different methods of fastening motors in place, so not all motors have mounting bases For the motors that do have mounting bases, this is how the motor is fastened in place The bolt-hole dimensions and... drive motor is capable of producing, the motor will not be able to turn and no mechanical work will be performed For mechanical work to be performed by an electric motor, the motor must be capable of producing enough torque to overcome the turning force requirements of the mechanical load The most common torque unit of measure for NEMA-rated electric motors is foot-pounds, and for IEC-rated motors... the design of the motor Figure  2-1 3  Full-voltage stator current graph Figure  2-1 4  Design B induction motor torque curve more detailed explanation The four torque measurements identified on the torque-speed graph in Figure  2-1 4 include: • Locked rotor torque—the torque that the motor develops at zero speed (rotor not turning) when the rated voltage and frequency are applied • Pull-up torque—the minimum... Stator winding slots Air vent holes Motor housing Mounting base Figure  2-1   Induction motor cutaway view with labels Through bolts holding The motor together © Cengage Learning 2013 Laminated iron stator core Chapter 2  Induction Motor Overview     13 Air Vent Holes The air vent holes of the motor pictured in Figure  2-1 are labeled on the bottom right of the picture Not all motors have air vent holes; some... on the load connection Not all motor shafts have key slots Many smaller motors use a flat area on the shaft where a set screw can be seated Motor Housing The motor housing, labeled on the lower left of Figure  2-1 , holds all the parts of the motor together All of the stationary parts of the motor, the stator core, conduit box, and mounting base are all mounted to the motor housing The end bells, which... the 50 turns at 0.5 V/t, 25 volts will be induced To help clarify the volts-per-turn principle, Figure  1-2 shows an iron core where both the energized coil and the induced coil have 100  turns each The energized winding has 100 turns, and is energized with 100 volts, which establishes a one volt-per-turn ratio Once the volts-per-turn ratio is established in the energized winding, it carries through to... IEC-rated motors it is newton-meters The torque foot-pound measurement is different from the work foot-pound measurement by the way it is calculated A torque foot-pound is defined as the force of one pound acting on a radius of one foot The product of any force in pounds and radius in feet will equal foot-pounds of turning torque For example, if a motor drives a pulley with a two-foot radius, and the belt... one turn of the coil Expanding magnetic field For the sake of this discussion, in Figure  1-5 , the 100-V supply voltage © Cengage Learning 2013 © Cengage Learning 2013 6      Chapter 1 Electromagnetic Induction Theory Figure  1-5   Inductor with 100-V source voltage Figure  1-6   Inductor with 100-V source and 100-V CEMF is going to push a single electron through the inductor coil The instant that electron... torque-speed curves NEMA has many motor letter classification designs by these characteristics (A,B,C, D, etc.), but the NEMA design B motor is the general purpose design, and is by far the most common The design B motor provides a good balance between locked rotor torque, locked rotor current, and full-speed torque that make it suitable for a wide range of electric motor applications Figure  2-1 3 shows . Two-Wire Motor Control 145 Two-Wire Motor Control Circuits 146 CHAPTER 13 Three-Wire Motor Control 151 Three-Wire Motor Control Circuits 152 CHAPTER 14 Control Circuits 159 Two-Wire Control Circuits. 112 CHAPTER 9 Magnetic Motor Starters 119 Denition 120 CHAPTER 10 Motor Starter Circuits 127 Motor Circuit Conductor Protection 128 Magnetic Motor Starter Circuit 128 CHAPTER 11 Motor Control Circuit. Induction Motors 39 Single-Phase Alternating Current (AC) Motors 40 Single-Phase Induction Motor Classications 45 CHAPTER 5 Induction Motor Electrical Connections 53 Motor Connections 54 CHAPTER 6 Motor