Abb Direct Torque Drive

ABB drives

Technical guide No. 1 Direct torque control the world’s most advanced AC drive technology

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Direct torque control | Technical guide No. 1

Technical guide No. 1 Direct torque control - the world’s most advanced AC drive technology

© Copyright 2011 ABB. All rights reserved. Specifications subject to change without notice. 3AFE58056685 REV C 6.6.2011

Technical guideNo. 1 | Direct torque control

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Direct torque control | Technical guide No. 1

Contents
Chapter 1 - Introduction ............................................................................7 General ..............................................................................................7 This manual’s purpose........................................................................7 Using this guide .................................................................................7 What is a variable speed drive? ...........................................................8 Summary ...........................................................................................8 Chapter 2 - Evolution of direct torque control ...........................................8 DC motordrives .................................................................................9 Features ........................................................................................9 Advantages ...................................................................................9 Drawbacks ..................................................................................10 AC drives -introduction ....................................................................10 AC drives - frequency control using PWM ..........................................11 Features ......................................................................................11 Advantages .................................................................................12 Drawbacks..................................................................................12 AC drives - flux vector control using PWM .........................................12 Features ......................................................................................12 Advantages .................................................................................13 Drawbacks..................................................................................13 AC drives - direct torque control ........................................................14 Controlling variables .....................................................................14 Comparison of variable speed drives .................................................15 Chapter 3 - Questions and answers ........................................................17 General............................................................................................17 Performance ....................................................................................18 Operation .........................................................................................24 Chapter 4 - Basic control theory .............................................................28 How DTCworks ...............................................................................28 Torque control loop...........................................................................29 Step 1 Voltage and current measurements ....................................29 Step 2 Adaptive motor model .......................................................29 Step 3 Torque comparator and flux comparator.............................30 Step 4 Optimum pulse selector ....................................................30 Speed control ..................................................................................31 Step 5 Torque reference controller .................................................31 Step 6 Speed controller ...............................................................31 Step 7...