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07/08/2002 PP.AFD.02.MotorBasics 1 of 55 Yaskawa Electric America Motor Basics

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Three Phase Motor Construction Stator Rotor Windings - Electromagnets Rotor bars

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Three Phase Motor Construction End View Rotor Stator Enclosure Air Gap Stator Windings Shaft

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Three Phase Motor Construction End View T1 T2 T2’ T3 T1’ T3’

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Motor Operation

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Three Phase Motor Construction T1 End View T2 T2’ T3 T1’ T3’ + + + + denotes current is moving away from you denotes current is moving away from you denotes current is moving towards you denotes current is moving towards you

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Rotation of the motor + + + N N S S S N T1T3T2 One Cycle* * - current waveform

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Rotation of the motor + + + N S N N S S T1T3T2 One Cycle* * - current waveform + + + N N S S S N

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Rotation of the motor + + + N N S S S N T1T3T2 One Cycle* * - current waveform + + + N N S S S N + + + N S N N S S

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Rotation of the motor + + + N N S S S N T1T3T2 One Cycle* * - current waveform + + + N N S S S N + + + N S N N S S + + + N N S S S N

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Rotation of the motor + + + N N S S S N T1T3T2 One Cycle* * - current waveform + + + N N S S S N + + + N S N N S S + + + N N S S S N + + + N N S S S N

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Rotation of the motor + + + N N S S S N T1T3T2 One Cycle* * - current waveform + + + N N S S S N + + + N S N N S S + + + N N S S S N + + + N N S S S N + + + N N S S S N

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Rotation of the motor + + + N N S S S N T1T3T2 One Cycle* * - current waveform + + + N N S S S N + + + N S N N S S + + + N N S S S N + + + N N S S S N + + + N N S S S N + + + N N S S S N

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Calculating Synchronous Speed of the Motor

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Poles & Synchronous RPM @ 60Hz 7200 = Synchronous RPM P 7200 = P Synchronous RPM

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Three Phase Motor Construction T1 End View T2 T2’ T3 T1’ T3’

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Three Phase Motor Construction T1 End View T2 T2’ T3 T1’ T3’

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Three Phase Motor Construction End View MagneticPoles T1a T2a T2a’ T1a’ T1b T2b T2b’ T3b T1b’ T3b’ T3b’ T3b

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What is Slip ? n To produce torque in an induction motor, current must flow in the rotor. n To induce current flow in the rotor, the rotor speed must be slightly slower than the synchronous speed. n The difference between the synchronous speed and the rotor speed (rated speed) is called the slip. Stator Flux Rotor Slip

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Calculating Motor Rated Speed Formula to find actual motor RPM N = 120 f P ( 1 - s ) Where: N - RPM of the motor f - Frequency in Hz P- Number of poles of the motor s- (N o - N) / N o

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Speed - Torque Curve (600%) Locked Rotor Torque (150%) Full Load Torque (100%) Pull Up Torque (125%) Breakdown Torque (200-250%) Rated Speed Synch Speed SPEED TORQUE CURRENT No Load Current (30%) Slip (300%) (300%) (200%)

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Speed - Torque Curve SPEED TORQUE

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Typical NEMA Design Characteristics 0 100% SPEED TORQUE 200% 300% 100% NEMA Design A n High breakdown torque n Normal starting torque n High starting current n Low full load slip n Used in applications that require: l Occasional overloads l Better efficiency

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Typical NEMA Design Characteristics 0 100% SPEED TORQUE 200% 300% 100% Design B NEMA Design B n Normal breakdown torque n Normal starting torque n Low starting current n Normal full load slip l less than 5% n General Purpose Motor Design A

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Typical NEMA Design Characteristics 0 100% SPEED TORQUE 200% 300% 100% Design C NEMA Design C n Low breakdown torque n High starting torque n Low starting current n Normal full load slip l less than 5% n Used in applications that require: l high breakaway torque Design A Design B

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Typical NEMA Design Characteristics 0 100% SPEED TORQUE 200% 300% 100% Design D NEMA Design D n High breakdown torque n High starting torque n Normal starting current n High full load slip l 5 - 13% n Used in applications that require: l high breakaway torque Design C Design A Design B

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Motor Nameplate Data

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Understanding the Nameplate HP- Horsepower n The horsepower figure stamped on the nameplate is the horsepower the motor is rated to develop when connected to a circuit of the voltage, frequency and number of phases specified on the motor nameplate.

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Rotational Horsepower Formula n The horsepower formula in simplified form HP = Torque x RPM Torque x RPM5250 Where: Torque - Amount of torque in lb.ft. RPM - RPM of the motor 5250 - constant obtained by dividing 33,000 by 6.28 HP x 5250 HP x 5250RPM Torque = OR

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Understanding the Nameplate RPM - Revolutions per Minute n The RPM value represents the approximate speed at which the motor will run when properly connected and delivering its rated output

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Understanding the Nameplate

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Voltage n The rated voltage figure on the motor nameplate refers to the voltage of the supply circuit to which the motor should be connected, to produce rated horsepower and RPM. Key piece of information when selecting an inverter.

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Effects of Voltage Variation on the Motor at 60Hz Low Voltage l Higher than normal current l Higher than normal motor temperature High Voltage l Higher than normal current l Lower than normal power factor

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Understanding the Nameplate Phase n The phase figure on the motor nameplate describes the alternating current system that the motor has been designed for. Key piece of information when selecting an inverter.

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Understanding the Nameplate Hz-Frequency n The frequency figure on the motor nameplate describes the alternating current system frequency that must be applied to the motor to achieve rated speed and horsepower.

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Understanding the Nameplate Amps n The amp figure on the motor nameplate represents the approximate current draw by the motor when developing rated horsepower on a circuit of the voltage and frequency specified on the nameplate. Key piece of information when selecting an inverter.

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Understanding the Nameplate NEMA Design n The NEMA Design rating specifies the speed torque curve that will be produced by the motor.

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Understanding the Nameplate Insulation Class n The insulation class letter designates the amount of allowable temperature rise based on the insulation system and the motor service factor.

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Insulation Class Information n Most common insulation classes are class B and F

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Understanding the Nameplate S.F. - Service Factor n The number by which the horsepower rating is multiplied to determine the maximum safe load that a motor may be expected to carry continuously Example - a 10HP motor with a service factor of 1.15 will deliver 11.5 horsepower continuously without exceeding the allowable temperature rise of its insulation class

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Understanding the Nameplate Frame n The frame designation refers to the physical size of the motor as well as certain construction features such as the shaft and mounting dimensions.

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Types of Motor Enclosures n Open Drip-proof (ODP) n Totally enclosed non-ventilated (TENV) n Totally enclosed fan cooled (TEFC) n Totally enclosed blower cooled (TEBC)

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Types of Motor Enclosures ODP n Open drip-proof n Ventilating openings permit passage of external cooling air over and around the windings of the motor. Small degree of protection against liquid or solid particles entering the enclosure.

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Types of Motor Enclosures TENV n Totally enclosed non-ventilated n Totally enclosed enclosure with no means of external cooling.

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Types of Motor Enclosures TEFC n Totally enclosed fan-cooled n Totally enclosed enclosure with external cooling means, such as a shaft connected fan

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Types of Motor Enclosures TEBC n Totally enclosed blower-cooled n Totally enclosed enclosure with external cooling means such as a separately controlled motor/blower

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TEFC Speed Ranges n Constant Torque4:1(15-60 Hz) n Constant Torque10:1(6-60 Hz) n Variable Torque1-60 Hz 2:1 (30-60 Hz) CT

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TENV/TEBC Speed Ranges n Constant Torque0 to Base Speed 100:1(0.6-60 Hz) 1000:1(0.06-60 Hz)

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Motor Retrofit Summary n RPM n Volts n Phase n Amps n NEMA Design n Frame + any prefix or suffix letter codes n Location n Mounting Orientation n Application n Enclosure Style n Motor Control Method n Inverter-Duty?

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Motor Basics Exercise n n Answer the following questions using your knowledge and/or the documents from this class. 1.) Write down the formula to calculate synchronous motor speed (please use the simplified form). 2.) To calculate the actual motor speed what has to be included in the above formula ? 3.) The majority of electric motors used in general purpose applications in industry today are what NEMA design ? 4.) A NEMA design D motor is characterized by very high breakdown torque, and a large percentage of slip ? (True or False) 5.) Name the two pieces of information needed off the motor nameplate when selecting an inverter.

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Motor Basics Exercise n n Answer the following questions using your knowledge and/or the documents from this class. 1.) Write down the formula to calculate synchronous motor speed (please use the simplified form). Voltage and Full Load Amps (FLA) 120 x f / P slip (120 x f / P) - slip NEMA design B True 2.) To calculate the actual motor speed what has to be included in the above formula? 3.) The majority of electric motors used in general purpose applications in industry today are what NEMA design? 4.) A NEMA design D motor is characterized by very high breakdown torque, and a large percentage of slip ? (True or False) 5.) Name two key pieces of information needed off the motor nameplate when selecting an inverter.

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07/08/2002 PP.AFD.02.MotorBasics 55 of 55 n Yaskawa Electric America Technical Training Services 09/06/2001 09/06/2001

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07/08/2002 PP.AFD.02.MotorBasics 56 of 55 n Yaskawa Electric America Technical Training Services n For training information, please: l Call us at 1-800-YASKAWA and select option #6 l Check out our website at www.yaskawa.com www.yaskawa.com l E-mail us at training@yaskawa.com

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