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APPLICATION OF MOTORS TO ADJUSTABLE
FREQUENCY DRIVESPART 1
Alan Lowe, Senior Electrical Consultant
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RISE TIMESREFLECTED WAVESBEARING CURRENTSCABLE SELECTIONIGBT
NON-AGENDA
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AGENDA
INTRODUCTIONNOMENCLATUREWHY USE AFDHORSEPOWER, SPEED, TORQUEMOTOR CAPABILITIES & LIMITATIONSTYPES OF LOADS
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PRE-TEST
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A “SPECIAL” MOTOR WILL BE REQUIRED FOR DRIVE APPLICATIONS:
A. ALWAYS
B. MOST OF THE TIME
C. RARELY
D. NEVER
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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
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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
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DRIVE NOMENCLATURE
IS IT---
VSD, ASD, VFD, OR AFD
?
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DRIVE NOMENCLATURE
VARIABLE VS. ADJUSTABLE
THE WEATHER OUTSIDE IS VARIABLE
THE TEMPERATURE IN YOUR HOME IS ADJUSTABLE
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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
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DRIVE NOMENCLATURE
BE CAREFUL--
“DRIVE”
CAN MEAN ALMOST ANYTHING
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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.
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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
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WHY USE AN AFD?
E. ACCELERATION OF HIGH INERTIA LOAD
F. TO AVOID FREQUENT MOTOR STARTING
G. AS A REPLACEMENT FOR GEARING
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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?
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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?
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IT’S A DRIVE SYSTEM !
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THE MOTOR
WHAT DO WE MEAN BY A 100 HP, 1800 RPM
MOTOR?
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HORSEPOWER
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MOTOR HORSEPOWER
1 HP MOTOR33,000 FT-LBS/MIN
550 FT-LBS/SEC
746 WATTS / MOTOR EFFICIENCY
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MOTOR HORSEPOWER
5252RPMTHP
RPMHPT 5252
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60 75 904530150
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50
75
100
125
% R
ATE
D H
P%
RA
TED
TO
RQ
UE
0
APPLIED FREQUENCY (HERTZ)
CONSTANT TORQUE CONSTANT HP
MOTOR HORSEPOWER
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MOTOR HORSEPOWER
Generally a motor can deliver:
Rated TORQUE at and below base rated speed.
Rated HORSEPOWER at and above base rated speed.
But there are some LIMITATIONS!
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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
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LIMITATIONS: REDUCED COOLING
NEMA MG-1 FIGURE 30-2
1.0 S.F.MOTOR
1.15 S.F.
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LIMITATIONS: HARMONIC HEATING
NEMA MG-1 FIGURE 30-3
IT DEPENDS ON THE MOTOR.
IT DEPENDS ONTHE DRIVE.
THERE’S NO ESTABLISHEDMETHOD OFCALCULATION.
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MOTOR TORQUE vs. SPEED
RATED TORQUE = HP x 5252 / RPM
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MOTOR TORQUE vs. SPEEDLRT per NEMA MG-112.38.1TABLE 12-2
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MOTOR LOCKED ROTORTORQUE
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MOTOR TORQUE vs. SPEED
P.U. TORQUE perNEMA MG1, 12.40.1
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MOTOR PULL UP TORQUENEMA MG-1 12.40.1 PULL UP TORQUE FOR DESIGN A AND B MOTORS
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MOTOR TORQUE vs. SPEED
BD TORQUE perNEMA MG1, 12.39.1
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MINIMUM BREAKDOWN TORQUE
PER NEMA MG-1 12.39.1 FOR DESIGN A & B MOTORS
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BREAKDOWN TORQUE
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.
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LIMITATIONS: TORQUE
NEMA MG-1 FIGURE 30-4
B.D. TORQUE= 77.7% TR
2/3TR x 3/2SR =HPR
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TORQUE vs. SPEED
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TORQUE vs. SPEED ON AFD
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TORQUE vs. SPEED ON AFD
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TORQUE vs. SPEED ON AFD
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MOTOR TORQUE vs. SPEED
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MAXIMUM SAFE SPEED
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LIMITATIONS: MAX SAFE SPEED
POLES / RPM 200% / 120Hz 150% / 90Hz 125% / 75Hz
2 / 3600 Up to 5 HP Up to 30 HP Up to 50 HP
4 / 1800 Up to 20 HP Up to150 HP Up to 300 HP
6 /1200 Up to 75 HP Up to 350 HP N/A
ALLOWABLE OVERSPEED OPERATION
BASED ON NEMA MG 1 TABLE 30-1
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LOAD CHARACTERISTICS
VARIABLE TORQUE
CONSTANT TORQUE
CONSTANT HORSEPOWER
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VARIABLE TORQUE LOAD
CENTRIFUGAL PUMPS
FANS
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VARIABLE TORQUE LOAD
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21
2
1
RPMRPM
HH
2
1
2
1
RPMRPM
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31
2
1
RPMRPM
HPHP
AFFINITY LAWS FOR CENTRIFUGAL PUMPS
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VARIABLE TORQUE LOAD
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VARIABLE TORQUE LOAD
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VARIABLE TORQUE LOAD
102% LOAD @ 65 HZ
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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.
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CONSTANT TORQUE LOADS
CONVEYORS
POSITIVE DISPLACEMENT PUMPS
CRANES
PAPER MACHINE SECTIONS
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CONSTANT TORQUE LOAD
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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.
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CONSTANT HORSEPOWER
UNWIND STAND OF A WINDER
A CENTER WIND REEL
PUNCH PRESS
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CONSTANT HORSEPOWER
MOTOR MUST PROVIDE 165 FT-LBS AND 127.3 RPMOR
HP = 165 x 127.3 /5252 = 4
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CONSTANT HORSEPOWER
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CONSTANT HORSEPOWER
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CONSTANT HORSEPOWER
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SELECT MOTOR FOR CONSTANT HORSEPOWER LOADS1.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”.
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SELECT MOTOR FOR CONSTANT HORSEPOWER LOADS
3.ALL PARTIES MUST BE INVOLVED:a) DRIVE VENDORb) MOTOR VENDORc) DRIVEN EQUIPMENT VENDORd) END USER
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REMEMBER!
IN OUR SOCIETY: IAS
THE
APPLICATION MATTERS
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APPLICATION OF MOTORS TO ADJUSTABLE FREQUENCY DRIVES
END PART 1
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APPLICATION OF MOTORS TO ADJUSTABLE FREQUENCY DRIVES
QUESTIONS?
770-688-2575
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PPIC 2013 ANNUAL CONFERENCE
PULP AND PAPER INDUSTRY COMMITTEE2014 ANNUAL CONFERENCE
ATLANTA, GEORGIAJUNE 23, 24 & 25
