DC motor
Copyright © 2003
by John Wiley & Sons, Inc.
1-1
A basic dc-machine
N
N
F
v
I
B
S
E
B
S
B
a
B
b
N
a) Force
b) EMF
F = BIL
E = BvL
S
Rotating turn
The commutator
Copyright © 2003
by John Wiley & Sons, Inc.
1-2
DC-Motor Equivalent Circuit
• The mechanical system can also be represented as
an electrical circuit
Copyright © 2003
by John Wiley & Sons, Inc.
1-3
Four-Quadrant Operation of DC-Motor
Drives
• High performance drives may operate in all four
quadrants
Copyright © 2003
by John Wiley & Sons, Inc.
1-4
Converter for DC-Motor Drives
• Four quadrant operation is possible
Copyright © 2003
by John Wiley & Sons, Inc.
1-5
DC-Motor Drive Torque-Speed
Characteristics and Capabilities
• With permanent magnets
Copyright © 2003
by John Wiley & Sons, Inc.
1-6
DC-Motor Drive Capabilities
• Separately-Excited field
Copyright © 2003
by John Wiley & Sons, Inc.
1-7
Controlling Torque, Speed and Position
• Cascaded control is commonly used
Copyright © 2003
by John Wiley & Sons, Inc.
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Small-Signal Representation of DC
Machines
• Around a steady state operating point
Copyright © 2003
by John Wiley & Sons, Inc.
1-9
Electrical Time-Constant of the DC Machine
• The speed is assumed constant
Copyright © 2003
by John Wiley & Sons, Inc.
1-10
Mechanical Time-Constant of the DC
Machine
• The load-torque is assumed constant
Copyright © 2003
by John Wiley & Sons, Inc.
1-11
Underground trainset, C15
Main data
Line voltage:
500 – 770 V dc
Nom. speed:
80 km/h
Acceleration:
1,1 m/s^2
(6 sec to 25 km/h)
Weight:
2 x 36 tons (full load)
Nom. power:
4 x 2 x 80 kW
Track width:
1435 mm
Copyright © 2003
by John Wiley & Sons, Inc.
1-12
Main circuit, C15
Copyright © 2003
by John Wiley & Sons, Inc.
1-13