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