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Yaskawa Electric America Motor Basics 07/08/2002 PP.AFD.02.MotorBasics 1 of 55 Three Phase Motor Construction Windings - Electromagnets Rotor bars Rotor Stator Three Phase Motor Construction Stator Windings Enclosure Air Gap Stator Rotor Shaft End View Three Phase Motor Construction T1 T2’ T3’ T3 End View T2 T1’ Motor Operation Motor Operation Motor Operation Motor Operation Three Phase Motor Construction T1 denotes current +is moving away from you + T2’ T3’ + + T3 End View T2 T1’ denotes current is moving towards you Rotation of the motor One Cycle* T1 T3 T2 + + S N * - current waveform + Rotation of the motor One Cycle* T1 T3 T2 + + S + N + + + * - current waveform Rotation of the motor One Cycle* T1 T3 T2 + + S + + + N + + + + * - current waveform Rotation of the motor One Cycle* T1 T3 T2 + + S + + + N + + N + + + S + * - current waveform + Rotation of the motor One Cycle* T1 T3 T2 + + S + + + N + + N + + + N + + + S + * - current waveform + Rotation of the motor One Cycle* T1 T3 T2 + + S + + + N + + N + + + N + + + N + + S + * - current waveform + + Rotation of the motor One Cycle* T1 T3 T2 + + S + + + + + S N + + N N + + + N + + + N + + S + * - current waveform + + + Calculating Synchronous Speed of the Motor 120 f No P Poles & Synchronous RPM @ 60Hz Magnetic Poles 2 4 6 8 7200 P = Synchronous RPM 3600 1800 1200 900 Synchronous RPM 7200 Synchronous RPM = P Three Phase Motor Construction T1 T2’ T3’ T3 End View T2 T1’ Three Phase Motor Construction T1 T2’ T3’ T3 End View T2 T1’ Three Phase Motor Construction T3b T2b’ T1b’ T1a T3b’ T2b T3b’ T2a T1a’ T1b End View T2a’ T3b Magnetic Poles What is Slip ? To produce torque in an induction motor, current must flow in the rotor. To induce current flow in the rotor, the rotor speed must be slightly slower than the synchronous speed. The difference between the synchronous speed and the rotor speed (rated speed) is called the slip. Flux Stator Slip Rotor 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 - (No - N) / No Speed - Torque Curve (300%) (600%) Slip TORQUE CURRENT (300%) (200%) Locked Rotor Torque (150%) Breakdown Torque (200-250%) Pull Up Torque (125%) Full Load Torque (100%) No Load Current (30%) SPEED Rated Speed Synch Speed Speed - Torque Curve TORQUE SPEED Typical NEMA Design Characteristics NEMA Design A High breakdown torque Normal starting torque High starting current Low full load slip TORQUE 300% Used in applications that require: Occasional overloads Better efficiency 200% 100% 0 SPEED 100% Typical NEMA Design Characteristics NEMA Design B 300% Normal breakdown torque Normal starting torque Low starting current Normal full load slip less than 5% TORQUE Design A 200% 100% Design B General Purpose Motor 0 SPEED 100% Typical NEMA Design Characteristics NEMA Design C Low breakdown torque High starting torque Low starting current Normal full load slip less than 5% TORQUE 300% Design C Design A 200% 100% Design B Used in applications that require: high breakaway torque 0 SPEED 100% Typical NEMA Design Characteristics NEMA Design D 300% Design D High breakdown torque High starting torque Normal starting current High full load slip 5 - 13% Design C TORQUE Design A 200% 100% Design B Used in applications that require: high breakaway torque 0 SPEED 100% Motor Nameplate Data Understanding the Nameplate HP- Horsepower 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. Rotational Horsepower Formula HP = The horsepower formula in simplified form Torque x RPM OR Torque = 5250 HP x 5250 RPM Where: Torque - Amount of torque in lb.ft. RPM - RPM of the motor 5250 - constant obtained by dividing 33,000 by 6.28 Understanding the Nameplate RPM - Revolutions per Minute The RPM value represents the approximate speed at which the motor will run when properly connected and delivering its rated output Understanding the Nameplate Poles 2 4 6 8 Synchronous RPM 3600 1800 1200 900 Typical Nameplate RPM 3450 1725 1140 850 Understanding the Nameplate Voltage 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. Effects of Voltage Variation on the Motor at 60Hz High Voltage Low Voltage Higher than normal current Higher than normal motor temperature Higher than normal current Lower than normal power factor Understanding the Nameplate Phase 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. Understanding the Nameplate Hz-Frequency 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. Understanding the Nameplate Amps 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. Understanding the Nameplate NEMA Design The NEMA Design rating specifies the speed torque curve that will be produced by the motor. Understanding the Nameplate Insulation Class The insulation class letter designates the amount of allowable temperature rise based on the insulation system and the motor service factor. Insulation Class Information Most common insulation classes are class B and F Insulation Class A B F H Ambient Temp. 40oC 40oC 40oC 40oC Temp. Rise 65oC 90oC 115oC 140oC Total Temp. 105oC 130oC 155oC 180oC Understanding the Nameplate S.F. - Service Factor 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 Understanding the Nameplate Frame The frame designation refers to the physical size of the motor as well as certain construction features such as the shaft and mounting dimensions. Types of Motor Enclosures Open Drip-proof (ODP) Totally enclosed non-ventilated (TENV) Totally enclosed fan cooled (TEFC) Totally enclosed blower cooled (TEBC) Types of Motor Enclosures ODP Open drip-proof 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. Types of Motor Enclosures TENV Totally enclosed non-ventilated Totally enclosed enclosure with no means of external cooling. Types of Motor Enclosures TEFC Totally enclosed fan-cooled Totally enclosed enclosure with external cooling means, such as a shaft connected fan Types of Motor Enclosures TEBC Totally enclosed blower-cooled Totally enclosed enclosure with external cooling means such as a separately controlled motor/blower TEFC Speed Ranges Constant Torque 4:1 (15-60 Hz) Constant Torque 10:1 (6-60 Hz) Variable Torque 1-60 Hz 2:1 (30-60 Hz) CT TENV/TEBC Speed Ranges Constant Torque 0 to Base Speed 100:1 (0.6-60 Hz) 1000:1 (0.06-60 Hz) Motor Retrofit Summary RPM Volts Phase Amps NEMA Design Frame + any prefix or suffix letter codes Location Mounting Orientation Application Enclosure Style Motor Control Method Inverter-Duty? Motor Basics Exercise 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. Motor Basics Exercise 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). 120 x f / P 2.) To calculate the actual motor speed what has to be included in the above formula? slip (120 x f / P) - slip 3.) The majority of electric motors used in general purpose applications in industry today are what NEMA design? NEMA design B 4.) A NEMA design D motor is characterized by very high breakdown torque, and a large percentage of slip ? (True or False) True 5.) Name two key pieces of information needed off the motor nameplate when selecting an inverter. Voltage and Full Load Amps (FLA) Yaskawa Electric America Technical Training Services 09/06/2001 07/08/2002 PP.AFD.02.MotorBasics 55 of 55 Yaskawa Electric America Technical Training Services For training information, please: Call us at 1-800-YASKAWA and select option #6 Check out our website at www.yaskawa.com E-mail us at [email protected] 07/08/2002 PP.AFD.02.MotorBasics 56 of 55