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8/3/2019 VVD Training

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Variable Speed Drives

Presented by: Nguyen Huu Loi


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PART 1


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ENERGY:

The motor changes electric energy into mechanical work which, once adapted to theproduction needs, becomes the effective work.

The sizing of the mechanical system and of the motor will be performed from those dataabout the effective work, in order to:

Ensure the energy transfer,

Limit mechanical and electrical losses.

WORK:

Work is the product of a force by a distance covered under the effect of that force. It isexpressed in joules and is independent from time.

As far as an angular motion is concerned, it is the work of a force torque whose action isequal to 2F1 x r. This action which is commonly called torque, is expressed inNewton-meters.


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WORK

Linear motion

A B

F

Work = force x distance

W(J) = F(N) x I(m)

Angular Motion

r

F

A

B rB

A

F1

F1

Work = force x distance

W = 2F1x r

W(J) = C(Nm) x (rd)


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POWER - TORQUE - SPEED

Transportation of 50 kg in one go Transportation of 5 kg in 10 times

WORK WORK


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FOR AN ANGULAR MOTION:

Hence:P(w) = T(Nm) x (rd/s)

POWERt

W

t

T

t

WP

t

and: angular speed in

radians/second

Power is defined by WORK divided by the total time spent to perform the task.


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The mechanical power required by the application represents the

ability of the motor to provide a work in a given time.

The rated power corresponds to the work provided in one

second by the motor in permanent normal state. It is expressed

in WATT.


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THE RESISTANT TORQUE

It is opposed to the motion whatever the direction of the rotation.

The machine is driven by the motor.There are several types of resistant torques:

- Constant resistant torque: Tr = constant

- Resistant torque proportional to speed: Tr = k

- Resistant torque proportional to square speed: Tr = k2

- Resistant torque inversely proportional to speed:

- Pull-up torque or starting overtorque

- Some machines have a high variation of torque

THE TRAILING (OVERHAULING) TORQUE

This makes the motion easier whatever the direction of the rotation.

The machine drives the motor.


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POWER:

Power is proportional to speed.

P = Tr , Tr = constant P = k

MACHINES:

Conveyor belts

Conveyors, Hoisting & Lift(80% of the cases)


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AMACHINES WITH CONSTANT RESISTANT TORQUE

Tr = constant

Speed

Tr

0 Torque

Graph


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POWER:

The power changes according to the square speed.

P = Tr , Tr = k P = k2

MACHINES: Rare cases (some worm conveyors based on theprinciple of Archimedean screw and spiral pumps).


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B MACHINES WITH RESISTANT TORQUE PROPORTIONAL TOSPEED

Tr = kSpeed

Torque0

Tr

Graph


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POWER:

The power changes according to the cube of the speed.

P = Tr , Tr = k2 P = k3

MACHINES:

Centrifugal pumpsVentilators


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CMACHINES WITH RESISTANT TORQUE PROPORTIONAL TOSQUARE SPEED TR = K2

Speed

Torque

0

Tr

Graph


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POWER:

The power is constant:

P = Tr , P = k

MACHINES:

Machines tools broaches (cutter bar or bit)

Windings and unwinding machines

k

Tr

Textile machines


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D MACHINES WITH RESISTANT TORQUE INVERSELY

PROPORTIONAL TO SPEED

k

Tr

Torque

Speed

Maximum

speed

Minimum

speedMinimum

torque0 Maximum

torque

Tr

Graph


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E PULL-UP TORQUE OR STARTING OVERTORQUE

Torque

Speed Tr = constant

Tr = k

Tr = k2

0Tp

PULL-UP TORQUE

kTr

Graph


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PART 2


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- Reduction of Mechanical Stress

Importance of Speed Control

Speed

TimeDECACCLift & Elevator


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-Reduction of Current peaks, voltage dropsand protection motor


I/In

N/Ns0

1

2

3

This curve willchange

according tothe load


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- Process Regulation


Conveyor


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- Power Saving


HVAC System


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Methods of Varying Motor Speed

Mechanical method Clutch Variable Gear Reducers

Electrical method Variable transformers Steps resistors Motor Winding Electronic motor drives


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Where it is commonly used ?

Constant Torque loads, Hoisting & Lift Conveyors Crushers

Variable Torque loads Pumps Fans Beam Winders


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M

Line

Frequencydrive

3 PhaseMotor

AC

DC

PWM

PWM -Pulse Width Modulated wave

Basic Theory


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Fv -Frequency VariableFc -Frequency Carrier

Fv

Fc

PWM wave


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TECHNOLOGY

TYPICAL POWER DIAGRAM


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We have the definition to calculate the speed of the motor bases on the frequency and

number poles of the rotor:

The function of the inverter is changing the speed of the motor and keeping the moment of

the motor is a constant at any speed. In order to do so, the flux must be a constant

according to the formula below:

T = K I cos = constant

We can see that the moment is propositional to the current of the motor and it will be a

constant like:

T = constant if = constant

60f

Nsp


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In an asynchronous motor, the stator create a flux:

= L I At the voltage U, and frequency is f.

The Ohm law is: U = Z I

The impedance of the solenoid (without resistance) is :Z = L So :U = L I

is represented by: = 2 f

We have the current of the motor :

The flux is finally calculated :

In order to keep the flux in constant, i.e moment is contant, the ratio must be a constant at any speed of the

motor.

Conclusion: with the inverter, the voltage and frequency are changed propositionally.

f LI u

2

12

Uf

cst UF

cst

UF


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PART 3


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CENTRIFUGAL LOADS

70% OF ALL CONSUMED ELECTRICAL ENERGY

IS:

PUMPS

FANS

BLOWERS

COMPRESSORS


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Pumpingis an art of moving liquid and gasses

Pumps and Fans are designed to make water or air flow

and most of them are categorized asVariable Torque Load

InVariable Torque Loadthe torque required to drive the loadchanges according to the speed.As the speed of the load isreduced the torque required to drive it is decreased as a squaredof the speed


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Variable Torque Profile

0

0.2

0.4

0.6

0.8

1

%T

orque

0 0.2 0.4 0.6 0.8 1

% Speed


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Pump & Fans Princilple

CONSTRUCTION :ROTATING IMPELLER INSIDE OF A SPECIALLY SHAPEDSHELL


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PRINCIPLE :THE FLUID IS DRAWN IN AT THE AXIS ANDACCELERATED ALONG THE VANES OF THE IMPELLER



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PRINCIPLE :

THE FLUID IS MOVING FASTER AT THE TIPS OF THEIMPELLER, INCREASING BOTH ITS FLOW AND

PRESSURE



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PRINCIPLE :THE DIFFERENCE IN PRESSURE IS ALSO THE FORCETHAT DRAWS MORE FLUID INTO THE AXIS



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Typical Pump Curve

0

20

40

60

80

100

120

140

160

0 200 400 600 800 1000 1200 1400 1600

Flow

Pressure

Reminder

60

50

4030

Point A


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TYPICAL OUTPUT CONTROLS

THROTTLE VALVES

OUTLET DAMPERS

INLET VANES

MECHANICAL SPEEDCHANGES


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A SCARY ANALOGY

CONTROLLING A SYSTEM

LIKE THIS IS LIKE DRIVING ACAR WITH YOUR FOOT TO THE

FLOOR ON THEACCELERATOR WHILECONTROLLING THE SPEEDWITH A BRAKE.


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Variable Torque Loads

Fans and Pumps are designed to make air or water flow.As

the rate of flow increases, the air or water is has greaterchange in speed put into it by the fan or pump,increasingit inertia.

The effect that reduced speed has on variable torquefan or pump are summarized by set of rules known as the

AFFINITY LAW .

VSD Relation to Energy Savings


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0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

% Speed

Flow

Affinity Law

- Flow produced by the device is proportional to the motor speed

1st Law


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0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

% Speed

Pressure

- Pressured produced by the device is proportional to the motor speed squared.

Affinity Law

2nd Law


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0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

% Speed

Power

- Power produced by the device is proportional to the motor speed cubed

Affinity Law

3rd Law


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0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

% Speed

%Fl

ow,Pressure,H

P

FlowPressure

Horse Power

Affinity Law


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THROTTLE VALVE vs VSD

0

20

40

60

80

100

120

THROTTLE VALVE

VFD

PERC

ENTPOWER

PERCENT FLOW

10040


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INLET VANES vs VSD

0

20

40

60

80

100

120

INLET VANES

VFD

PERC

ENTPOWER

PERCENT FLOW

100

F l


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Cost to run a motor at 100% speed:

(Power) x (Time) x ($/VND/KWhr)

Cost to run a motor with variable speed drive

(%speed) for (%time) is to:(Power) x (%speed)3x (%time) x ($/VND/KWhr)

Savings

Cost w/o Drive - Cost w/ Drive

Formula :


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Example:

-Consider a 50 Hp (37.3 KW) drive at 2000 VND/KWhrrunning at 250 days a year for 10 hrs per day (2500 hrs).

Cost to run the motor at 100% speed

= (37.3 KW) x (2500 hrs) x (2000 VND/KWhr)

= 186.5 MVND


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Annual Duty Cycle using Drives

100

80

60

40

20

0

%Speed625 hrs.

625 hrs.

1250 hrs.

100% speed for 25% time= (37.3KW) x (1.0)

3x (625) x (2000 VND/KWhr)

= 57.625 MVND

80% speed for 50% time= (37.2KW) x (0.8)3x (1250) x (2000 VND/KWh= 47.616 MVND

60% speed for 25% time= (37.2KW) x (0.6)

3x (625) x (2000 VND/KWhr)

= 10.044 MVND


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Estimated yearly cost of saving based on use

= 186.5 115.285

Total cost based on duty cycle

= 57.625 + 47.616 + 10.044= 115.285 MVND

= 71.215 MVND

= 4.522 USD


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PART 4


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Flux Vector Control

Constant Speed

Reference

Set point

Rotary Encoder

Motor

Tacho & Pulse generatorfeedback option card

ATV58

Drive


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Motor 1 Motor 2

Motor Switching option

2 Motor performing differentfunction

Parameter Switchingoption card

ATV 58

PI Regulation


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PressureSensor

Pump

PI Regulation

Constant Pressure

Gauge

ATV58Drive

Reference

Set point

Pipe Line

ATV38Drive


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Automatic catch on the fly with speed retrieval

When the mains supply returns, the productcarries out a speed search andre-accelerates on the ACC ramp

N

ATV58 & ATV18

acceleration ramp

speed retrieval

without speed retrieval

U

Operatingvoltage

t

t

Power Interruption

Operatingspeed

ATV58Drive

ATV38

Drive


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A very completebasic product

Operator terminalon the drive or on the enclosure door

5 languagesdownloading of 4 files

PC software under Windows 95Disk upload / down load

Programming terminaladjust config storage

Program and mornitor byPowerSuiteSoftware

Catalogued option cards tosuit your needs

I/O extension

multiparameter

pump switching


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Built-in Modbus RS485

communication port

Remotable display unit

ATV58 X 4


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Built-in Modbus RS485

communication port

One dialogue multi-drive

Control by PC or PLC

ATV58

PC HMI PLC

X 4

Fast communication cards


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Fast communication cards

FIPIO ; Modbus + Interbus-SProfibus DP

AS-IDevice-NetCan OpenUnitelwayEthernet

ATV58

Communicationoption card

PLC

PC

PLC

ATV31

Pump Switching Option


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Pump Switching Option

Flow Rate

Number of Pumps

PV

PV

PV

PV

P1 P1 P1

P2 P2

P3

PV P1 P2 P3

Pressure Measurement

ATV 58

Sensor

Power Line

MotorStarter

Gauge

Flow

MotorStarter

MotorStarter

Motor Switchingoption card


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