dtc

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Welcome to the future of drives

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G N V SUBBA RAOBUSINESS MANAGER - AC DRIVES.

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Basic Motor Principle

ControlVariables

Torque Speed

Position

N

S

I

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DC Drive

DC Drive

T

=DC

SpeedControl

TorqueControl

Features:

Torque control is direct

Controlling variables:

Armature current

Field current

Field orientation via

Mechanical commutator

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DC Drive

DC Drive

T

=DC

SpeedControl

TorqueControl

Advantages:

Accurate and fast torquecontrol

High dynamic response

Simple to control

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DC Drive

DC Drive

T

=DC

SpeedControl

TorqueControl

Drawbacks:

Reduced reliability ofmotor

Regular maintenance

Motor costly to purchase

Needs encoder forfeedback

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AC Drive - Frequency Control

The AC Motor is:

Small - kW for kW

Very Robust

Simple in design

Light and Compact

Requires minimalmaintenance

Low Cost

Frequency control

AC

V

fFreq. ref.Modu-lator

V/Fratio

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Features:

Controlling variablevoltage and frequency

Flux provided withconstant V/F ratio

Load dictates the torquelevel

Simulation of variable ACsine wave usingmodulator (PWM)

Open-loop drive

Frequency control

AC

V


V/Fratio

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Frequency control

AC

V


V/Fratio

Advantages:

Low cost

No feedback device

required - Simple

Controls robust AC motor

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Drawbacks:

Ignores the motor status

Not torque controlling

Field orientation not used

A delaying modulatorused

Frequency control

AC

V


V/Fratio

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AC Drive - Flux Vector Control

Flux vector control

T

AC

V

f

Torquecontrol

Modu-lator

Speedcontrol

Features:

Field oriented control -simulates DC drive

Motor electricalcharacteristics aresimulated - Motor Model

Torque controlledindirectly

Closed-loop drive

Modulator needed

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Flux vector control

T

AC

V

f

Torquecontrol

Modu-lator

Speedcontrol

Advantages:

Good torque response

Accurate speed control

Can provide full torque atzero speed

Performance approaching

DC drive

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Flux vector control 3

T

AC

V

f

Torquecontrol

Modu-lator

Speedcontrol

Drawbacks:

Feedback is needed

Cost

Reliability

Modulator provides delayto performance

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Direct Torque Control

Direct Torque Control DTC 4

SpeedControl

TorqueControl AC

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DC Drive 1 Frequency control 2

Direct Torque Control DTC 4

T

=DC

SpeedControl

TorqueControl

Flux vector control 3

AC

V


V/Fratio

T

AC

V

f

Torquecontrol

Modu-lator

Speedcontrol

SpeedControl

TorqueControl AC

Evolution of drives to - DTC

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Why Direct Torque Control - DTC ?

Better product quality

Better Speed Accuracy

Better Torque Control

Less down time

Tripless Drives

Less Harmonics

Fewer products to support

Universal Drive

Comfortable working environment

Less noise

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DTC Operating Principle

How does DTC work?

Direct Torque Control DTC

SpeedControl

TorqueControl AC

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DTC Torque Control

=

3~

1

2 3

3

Torque control

FIRST EVER

TORQUE-CONTROLLEDOPEN-LOOP ACDRIVE

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DTC Motor Model

=

3~

Fastest ever developed

Calculations 40 000 timeseach second

Most advancedmathematics Exact calculation of flux even

at zero speed

NO TACHO FEEDBACKNEEDED

2 3

MotorModel

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Torque Comparator

=

3~

Compares calculated and

reference values 40 000times each second3

MotorModel

REF

ACT

Com-parator

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Optimal Switching Logic

=

3~

Input from Comparator,

when switching isneeded Just-in-time switching

Determines the optimalswitch combination

Motor state known at alltimes

-> Instead of fuzzy logic

CRYSTAL CLEAR LOGIC

Optimalswitching

Logic

MotorModel

Com-parator

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Integrated Drive & Motor Control

=

3~

No separate modulator

needed Direct control of main motor

parameters

Every single voltage

pulse (switching)controlled separately No wasted switchings

Atom level in AC drivecontrol

Optimalswitching

Logic

MotorModel

Com-parator

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Optimal Torque Response

Typical torque step

response times:DTC 1...2 ms

Flux vector 10...20 ms

PWM over 150 ms

MOTOR IS THE LIMITINGCOMPONENT, NOT THEINVERTER

Torque:

PWM

DTC

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DTC Performance

Slow reversing: full torque over zero speed Rapid acceleration: starting torque

Load impulse: dynamic speed accuracy

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DTC - Direct Torque Control

The ULTIMATE step in motor controlling

Outperforms all AC and DC drives

Torque response 10 times faster than any open-loop drive

Dynamic speed accuracy 8 times than anyopen-loop drive

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Optimal torque response

Integrated torquecontroller andmodulator

Torque control in every25 s - 10 times fasterthan the best ACdrives, over 100 timesmore often than in DCdrives

Motor is the limiting

factor - not the inverter

I:

T:

PWM

DTC

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Starting properties

DC magnetizing

Automatic

With given time

Automatic start

Very quick starting

Automatic determination of starting condition

No restart delay

High starting torque (in normal control mode)

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Flux braking & optimization

Flux braking:

Like in DC injection, mechanical energy is fed into themotor

Unlike in DC injection, we can instantly continueoperation

Flux Optimization

The magnitude of flux can be reduced at low load

E.g. HVAC

Energy saving & less noise

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Other features of DTC

No limits with maximum decelerating and accelerating

Ripple (and motor losses) vs. switching frequencyoptimum

No fixed carrier frequency => acoustic noisereasonable

On line modulation gives possibilities to realize newkind of inverter functions

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High performance of DTC

Torque control without tacho

Repeatibility: +/- 1% of nominal value

Static accuracy: +/- 10% of nominal value

in all speeds (including zero )

Superior to scalar control

Torque step response < 1 ms when f < 35HZ

< 2 ms when f < 40HZ

< 7 ms when f < FWP

< 10 ms when f > FWP

FWP: field weakening point

ACV 700: about 10 ms

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Speed control performance

Without tacho

Static accuracy 10 % of nominal slip Temperature dependency taken into account

Very fast step response

Integrated speeed drop 0,4 %swith nominal load torque step

Good enough for most applications

With tacho

Static accuracy 0,01 %

Dynamic accuracy 0,2 %s

Better operation at low frequency

Enables position control

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Open loop DTC < 5 msec

Open loop flux vector > 100 msec

Closed loop flux vector 10 to 20 msec

Fast Torque Step Rise Time High Dynamic Speed Accuracy

Closed Loop

Flux vector

Open LoopDTC

Torque

Speed

Torque

Speed error

Open loop DTC 0.4 %sec

Open loop flux vector 3.0 %sec

Closed loop flux vector 0.4 %sec

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With a pulse encoder Without a pulse encoder

Torque Control

Resolution 1:10000 1:10000

Non-linearity 1 %* 4 %*

Repeatability 0.7 %* 1.0 %*

Torque step rise time 1 to 5 ms 1 to 5 ms

Speed Control

Resolution 1:20000 1:20000

Speed range 1:6000 1:3000

Static accuracy 0.01 % 0.10 %**Dynamic accuracy 0.2 %s 0.4 %s

* Nominal torque** 10 % of the motor slip

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No loss of accuracy by heavy speed impacts

Fast torque control allows high gain in speed control ==>

good speed accuracy Improved dynamic and static accuracy

Reacting to special situations

power losses

over and under voltages

rapid load changes

mechanical resonances

New features

flux braking, automatic start, regenerative braking etc

DTC is based on ultrafast calculation and control

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of torque

Flux vector control can calculate torque

control only at 1-3 ms intervals. A modulator is needed to calculate

switching times

Control response is around 10 ms

DTC can calculate torque control at 0.025 msintervals

Each switching is directly activated by torquecontrol

Control response is around 1 ms

L h i

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Less stress to mechanics

Backlash appears in gearboxes and couplings. Inbacklash range motor may accelerate leading tobacklash impact. Fast DTC control limits impact.

Mechanical resonances often appear due toelasticy of shafts or web and inertias of motor,

gearbox and driven machine. Fast DTCattenuates the resonances.

DTC C t B fit W b H dli g

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DTC Customer Benefits - Web Handling

One of worlds largest web machine manufacturers

Web winder in film finishing

exact torque control needed

With DTC, previous solutions can be replaced withtachless drive

Benefit to the customer

considerable cost saving (assembly & wiring of eachtacho equals the cost of a 30 kW motor)

Rewind station construction simpler and easier

DTC Customer Benefits Textile Industry

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DTC Customer Benefits - Textile Industry

One of the worlds largest textile machine manufacturers

Power-loss control of a ring spinningmachine

With DTC, drive reacts in 25 s to the power loss

Changes immediately from motoring to generating

Benefit to the customer

Controlled stop in 20...30 sec

No extra capacitors needed in the dc link

DTC Customer Benefits Lifts

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DTC Customer Benefits - Lifts

One of worlds largest lift manufacturers

With DTC, extremely rapid torque control

allows high gains in speed control

Excellent drive comfort for high performance lift

jerkfree at start & stop

Also, regenerative bridge integrated in the drive resulting incompact design

Energy savings, high power factor, and low harmonics to the line

Manufacturer refers to the drive as servo

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