application of motors to adjustable frequency drives part 1 alan lowe, senior electrical consultant

APPLICATION OF MOTORS TO ADJUSTABLE

FREQUENCY DRIVESPART 1

Alan Lowe, Senior Electrical Consultant

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RISE TIMES

REFLECTED WAVES

BEARING CURRENTS

CABLE SELECTION

IGBT

NON-AGENDA

3

AGENDA

INTRODUCTION

NOMENCLATURE

WHY USE AFD

HORSEPOWER, SPEED, TORQUE

MOTOR CAPABILITIES & LIMITATIONS

TYPES 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

5252

RPMTHP

RPM

HPT

5252

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60 75 904530150

25

50

75

100

125

% R

AT

ED

HP

% R

AT

ED

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. SPEED

LRT 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

22

21

2

1

RPM

RPM

H

H

2

1

2

1

RPM

RPM

Q

Q

32

31

2

1

RPM

RPM

HP

HP

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 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”.

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SELECT MOTOR FOR CONSTANT HORSEPOWER LOADS

3.ALL PARTIES MUST BE INVOLVED:

a) DRIVE VENDOR

b) MOTOR VENDOR

c) DRIVEN EQUIPMENT VENDOR

d) 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?

alan.lowe@amec.com or

770-688-2575

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PPIC 2013 ANNUAL CONFERENCE

PULP AND PAPER INDUSTRY COMMITTEE

2014 ANNUAL CONFERENCE

ATLANTA, GEORGIA

JUNE 23, 24 & 25