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Transcript 
Chapter 13
DC-Motor Drives
•These drives continue to be used
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-1
DC-Motor Structure
• With permanent magnets or a wound field
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-2
DC-Motor Equivalent Circuit
• The mechanical system can also be represented as
an electrical circuit
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-3
Four-Quadrant Operation of DC-Motor
Drives
• High performance drives may operate in all four
quadrants
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-4
DC-Motor Drive Torque-Speed
Characteristics and Capabilities
• With permanent magnets
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-5
DC-Motor Drive Capabilities
• Separately-Excited field
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-6
Controlling Torque, Speed and Position
• Cascaded control is commonly used
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-7
Small-Signal Representation of DC
Machines
• Around a steady state operating point
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-8
Electrical Time-Constant of the DC Machine
• The speed is assumed constant
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-9
Mechanical Time-Constant of the DC
Machine
• The load-torque is assumed constant
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-10
DC-Motor Drive: Four-Quadrant Capability
• If a diode-rectifier is used, the energy recovered
during regenerative braking is dissipated in a resistor
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-11
Ripple in the Armature Current
• Bi-polar and uni-polar voltage switchings
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-12
Control of Servo Drives
• A concise coverage is presented in “Electric Drives: An
Integrative Approach” by N. Mohan (www.MNPERE.com)
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-13
Effect of Blanking Time
• Non-linearity is introduced
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-14
Converters for Limited Operational
Capabilities
• Two switches for 2-quadrant operation and only one
switch for 1-quadrant operation
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-15
Line-Controlled Converters for DC Drives
• Large low-frequency ripple in the dc output of
converters
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-16
Four Quadrant Operation using Line
Converters
• Two options to achieve 4-quadrant operation
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-17
Effect of Discontinuous Current Conduction
• Speed goes up unless it is controlled
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-18
Open-Loop Speed Control
• Adequate for general-purpose applications
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-19
DC Drive Characteristics and Capabilities
• Line current in switch-mode
and line-converter drives
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 13 DC Motor Drives
13-20
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