APPLICATION OF MOTORS TO ADJUSTABLE FREQUENCY DRIVES PART

APPLICATION OF MOTORS TO ADJUSTABLE FREQUENCY DRIVES PART 1 Alan Lowe, Senior Electrical Consultant

NON-AGENDA ØRISE TIMES ØREFLECTED WAVES ØBEARING CURRENTS ØCABLE SELECTION ØIGBT 2

AGENDA ØINTRODUCTION ØNOMENCLATURE ØWHY USE AFD ØHORSEPOWER, SPEED, TORQUE ØMOTOR CAPABILITIES & LIMITATIONS ØTYPES OF LOADS 3

PRE-TEST 4

A “SPECIAL” MOTOR WILL BE REQUIRED FOR DRIVE APPLICATIONS: A. ALWAYS B. MOST OF THE TIME C. RARELY D. NEVER 5

A MOTOR APPLIED TO AN AFD MUST MEET WHICH OF THE FOLLOWING: A. NEMA M-G 1 PART 30 B. NEMA M-G 1 PART 31 C. IEEE 841 D. NEMA PREMIUM EFFICIENCY 6

OPERATING ON AN AFD A 100 HP, 1200 RPM MOTOR CAN DELIVER 100 HP A. BETWEEN 1200 AND 1500 RPM B. BETWEEN 600 AND 1200 RPM C. ALL OF THE ABOVE D. NONE OF THE ABOVE E. DON’T ASK ME—I JUST CAME FOR LUNCH 7

DRIVE NOMENCLATURE IS IT--VSD, ASD, VFD, OR AFD ? 8

DRIVE NOMENCLATURE VARIABLE VS. ADJUSTABLE THE WEATHER OUTSIDE IS VARIABLE THE TEMPERATURE IN YOUR HOME IS ADJUSTABLE 9

DRIVE NOMENCLATURE “SPEED” VS. “FREQUENCY” THERE ARE MANY KINDS OF ADJUSTABLE SPEED DRIVES: • DC MOTORS • CONE PULLEYS • STEAM TURBINE • MECH. DIFFERENTIALS • EDDY CURRENT CLUTCHES • ADJUSTABLE VOLTAGE DRIVES • ADJUSTABLE FREQUENCY DRIVES 10

DRIVE NOMENCLATURE BE CAREFUL-“DRIVE” CAN MEAN ALMOST ANYTHING 11

DRIVE NOMENCLATURE DRIVE: THE EQUIPMENT USED FOR CONVERTING AVAILABLE ELECTRICAL POWER INTO MECHANICAL POWER SUITABLE FOR THE OPERATION OF A MACHINE. A DRIVE IS A COMBINATION OF A POWER CONVERTER (CONTROL), MOTOR, AND ANY MOTOR MOUNTED AUXILIARY DEVICES. 12

WHY USE AN AFD? A. THE PROCESS REQUIRES IT B. THE PROCESS CAN BE IMPROVED BY IT C. ENERGY SAVINGS D. EASIER ON DRIVEN EQUIPMENT 13

WHY USE AN AFD? E. ACCELERATION OF HIGH INERTIA LOAD F. TO AVOID FREQUENT MOTOR STARTING G. AS A REPLACEMENT FOR GEARING 14

WHY WORRY ABOUT THE MOTOR? WHAT’S DIFFERENT? A. CAN THE MOTOR PRODUCE THE REQUIRED TORQUE THROUGHOUT THE OPERATING SPEED RANGE? B. WILL THE MOTOR HAVE ADEQUATE COOLING AT LOW SPEEDS? C. WILL HARMONICS FROM THE DRIVE CAUSE THE MOTOR TO OVERHEAT? 15

WHY WORRY ABOUT THE MOTOR? WHAT’S DIFFERENT D. WILL THE MOTOR FLY APART AT OVERSPEED? E. WILL THE DRIVE VOLTAGE WAVEFORM DAMAGE THE MOTOR WINDINGS? F. WILL THE DRIVE VOLTAGE WAVEFORM DAMAGE THE MOTOR BEARINGS? 16

IT’S A DRIVE SYSTEM ! 17

THE MOTOR WHAT DO WE MEAN BY A 100 HP, 1800 RPM MOTOR? 18

HORSEPOWER 19

MOTOR HORSEPOWER 33, 000 FT-LBS/MIN 1 HP MOTOR 550 FT-LBS/SEC 746 WATTS / MOTOR EFFICIENCY 20

MOTOR HORSEPOWER 21

MOTOR HORSEPOWER 22

MOTOR HORSEPOWER Generally a motor can deliver: ØRated TORQUE at and below base rated speed. ØRated HORSEPOWER at and above base rated speed. But there are some LIMITATIONS! 23

NEMA MG-1 § Part 30. 2 GENERAL PURPOSE MOTORS USED WITH ADJUSTABLE-VOLTAGE OR ADJUSTABLE-FREQUENCY CONTROL OR BOTH § Part 31 DEFINITE PURPOSE INVERTER FED POLYPHASE MOTORS 24

LIMITATIONS: REDUCED COOLING 1. 15 S. F. 1. 0 S. F. MOTOR NEMA MG-1 FIGURE 30 -2 25

LIMITATIONS: HARMONIC HEATING IT DEPENDS ON THE MOTOR. IT DEPENDS ON THE DRIVE. THERE’S NO ESTABLISHED METHOD OF CALCULATION. NEMA MG-1 FIGURE 30 -3 26

MOTOR TORQUE vs. SPEED RATED TORQUE = HP x 5252 / RPM 27

MOTOR TORQUE vs. SPEED LRT per NEMA MG-1 12. 38. 1 TABLE 12 -2 28

MOTOR LOCKED ROTOR TORQUE 29

MOTOR TORQUE vs. SPEED P. U. TORQUE per NEMA MG 1, 12. 40. 1 30

MOTOR PULL UP TORQUE NEMA MG-1 12. 40. 1 PULL UP TORQUE FOR DESIGN A AND B MOTORS 31

MOTOR TORQUE vs. SPEED BD TORQUE per NEMA MG 1, 12. 39. 1 32

MINIMUM BREAKDOWN TORQUE PER NEMA MG-1 12. 39. 1 FOR DESIGN A & B MOTORS 33

BREAKDOWN TORQUE IS PROPORTIONAL TO (V/HZ)2 ABOVE BASE SPEED BREAKDOWN TORQUE IS PROPORTIONAL TO (1/HZ)2 STARTING WITH 175% AT 60 HZ YIELDS 77. 7% RATED TORQUE AT 90 HZ. 34

LIMITATIONS: TORQUE B. D. TORQUE = 77. 7% TR 2/3 TR x 3/2 SR = HPR NEMA MG-1 FIGURE 30 -4 35

TORQUE vs. SPEED 36

TORQUE vs. SPEED ON AFD 37

TORQUE vs. SPEED ON AFD 38

TORQUE vs. SPEED ON AFD 39

MOTOR TORQUE vs. SPEED 40

MAXIMUM SAFE SPEED 41

LIMITATIONS: MAX SAFE SPEED ALLOWABLE OVERSPEED OPERATION POLES / RPM 200% / 120 Hz 150% / 90 Hz 125% / 75 Hz 2 / 3600 Up to 5 HP Up to 30 HP Up to 50 HP 4 / 1800 Up to 20 HP Up to 150 HP Up to 300 HP 6 /1200 Up to 75 HP Up to 350 HP N/A BASED ON NEMA MG 1 TABLE 30 -1 42

LOAD CHARACTERISTICS § VARIABLE TORQUE § CONSTANT HORSEPOWER 43

VARIABLE TORQUE LOAD § CENTRIFUGAL PUMPS § FANS 44

VARIABLE TORQUE LOAD AFFINITY LAWS FOR CENTRIFUGAL PUMPS 45

VARIABLE TORQUE LOAD 46

VARIABLE TORQUE LOAD 47

VARIABLE TORQUE LOAD 102% LOAD @ 65 HZ 48

SELECT MOTOR FOR VARIABLE TORQUE LOADS 1. MAKE SURE THE MOTOR CAN OPERATE SAFELY AT THE TOP SPEED REQUIRED BY THE LOAD. 2. MAKE SURE THE MOTOR CAN DELIVER THE REQUIRED HORSEPOWER AT THE TOP SPEED. 3. LOW END OPERATION IS NOT A PROBLEM. 49

CONSTANT TORQUE LOADS § CONVEYORS § POSITIVE DISPLACEMENT PUMPS § CRANES § PAPER MACHINE SECTIONS 50

CONSTANT TORQUE LOAD 51

SELECT MOTOR FOR CONSTANT TORQUE LOADS 1. MAKE SURE THE MOTOR CAN OPERATE SAFELY AT THE TOP SPEED REQUIRED BY THE LOAD. 2. MAKE SURE THE MOTOR CAN DELIVER THE REQUIRED TORQUE AT THE TOP SPEED. 3. BELOW 30 HZ GIVE YOURSELF SOME MARGIN, LIMIT LOADING TO 80% OF RATING. 4. BELOW 15 HZ CONSULT THE MOTOR MANUFACTURER. 52

CONSTANT HORSEPOWER § UNWIND STAND OF A WINDER § A CENTER WIND REEL § PUNCH PRESS 53

CONSTANT HORSEPOWER MOTOR MUST PROVIDE 165 FT-LBS AND 127. 3 RPM OR HP = 165 x 127. 3 /5252 = 4 54

CONSTANT HORSEPOWER 55

CONSTANT HORSEPOWER 56

CONSTANT HORSEPOWER 57

SELECT MOTOR FOR CONSTANT HORSEPOWER LOADS 1. MOTOR MUST BE ABLE TO DELIVER THE SPEED AND TORQUE REQUIRED AT THE FASTEST AND SLOWEST OPERATING SPEEDS. 2. THE MOTOR WILL BE OF SPECIAL DESIGN OR VERY MUCH “OVERSIZED”. 58