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ABB GroupMarch 17, 2014 | Slide 1
DC machines fundamentalsWiwiet Yuniarto
ABB GroupMarch 17, 2014 | Slide 2
DC machines fundamentalsHighlights
DC machines are well known for
Full torque from zero speed
Wide field weakening range
Excellent control behavior
Correlations
Field current and armature current are responsible fortorque
Armature voltage and armature current are responsible forpower
Size
DC machines are half the size of comparable standard ACmachines
ABB GroupMarch 17, 2014 | Slide 3
DC machines fundamentalsTorque and power compared to size
Poweris equal
Torqueis equal
P = 11 kWn = 1140 rpmM = 76 Nm
P = 11 kWn = 960 rpmM = 110 Nm
P = 11 kWn = 730 rpmM = 150 Nm
P = 22 kWn = 1440 rpmM = 150 Nm
P = 15 kWn = 960 rpmM = 150 Nm
P = 11 kWn = 730 rpmM = 150 Nm
ABB GroupMarch 17, 2014 | Slide 4
DC machines fundamentalsStator
Stator (field)
Stationary part
Provides the field (flux)
Field windings
Interpole and compensation windingseliminate unwanted effects
ABB GroupMarch 17, 2014 | Slide 5
DC machines fundamentalsRotor
Rotor (armature)
Moving part
Develops the torque
Armature winding
Shaft is the center axis
Commutator connected with windings
ABB GroupMarch 17, 2014 | Slide 6
DC machines fundamentalsCommutator
Commutator
Transfers energy
Fins are connected with the windings
Brushes provide electrical contact
Neutral zone is perpendicular to themain field
ABB GroupMarch 17, 2014 | Slide 7
DC machines fundamentalsCompactness
Typical ABB DMI machine
Can be used as motor and generator
The shaft is mounted between the bearings
The terminal box is used to connect the cables
ABB GroupMarch 17, 2014 | Slide 8
DC machines fundamentalsABB DMI machine
Terminal box includesconnectors
Non drive side withcommutator, analog tachoor encoder
Middle part with windings
Drive side with shaft
ABB GroupMarch 17, 2014 | Slide 9
DC machines fundamentalsTypical ABB DMI machines
Air cooled
Water cooled
ABB GroupMarch 17, 2014 | Slide 10
DC machines fundamentalsSeparately excited DC machine
Characteristics
Both armature and field are supplied by a separate powersource
Equivalent circuit diagram: Formulas:
RA
UA
IA
EMF
LA
Armature Excitation
UF
IF
c = ConstantT = TorqueF = Flux
dt
dIAEMF = UA - RA * IA - LA
T = c * IA *
n =c * EMF
ABB GroupMarch 17, 2014 | Slide 11
DC machines fundamentalsSeparately excited DC machine
Commutation limit
Field weakening factor:
nbase
UAN
IAN
IFN
TN
PN
UA
IA
IF
T
P
nnmaxCommutation limit
Armature voltage
Armature current
Field current
Torque
Power
f =nmaxnbase