ABB DCS 400 - Automatic Field Weakening; Calculated EMF; Correlation of Armature Voltage and EMF; Motor Name Plate

II K 4-30
Overview of Software
4.5.3 Automatic field weakening
Correlation of Armature Voltage and EMF
The DCS 400 drive calculates the true EMF and does
not take the Armature Voltage instead. EMF is
calculated by
EMF
NOM
= Arm Volt
NOM
- (Arm Cur
NOM
x Arm Resistance)
The Armature Resistance is measured during arma-
ture autotuning or can be entered manually. This
means, without load and thus without current you
will never get to full rated Armature Voltage but always
full speed.
Example:
Motor name plate
Armature Voltage (Ua) nominal: 440 V
Armature Current (Ia) nominal: 217 A
Field Voltagel (Uf) nominal: 220 V
Field Current (If) nominal: 4.6 A
Speed (n) nominal: 2250 rpm
Parameter settings
Arm Volt Nom (1.02): 440 V
Arm Cur Nom (1.01): 217 A
Field Volt Nom (1.04): 220 V
Field Cur Nom (1.03): 4.6 A
Base Speed (1.05): 2250 rpm
Max Speed (1.06): 2250 rpm
Armature Resistance (3.13) (Ra)
determined by Arm Autotuning: 230 mW
Calculated EMF:
EMF
NOM
= Ua
NOM
(1.02) - (Ia
NOM
(1.01) x Ra (3.13))
= 440 V - [217 A x 0,23 W]
= 440 V - 50V
EMF
NOM
= 390 V
Ua actual
Under full load condition, at full speed:
Ua
actual (3.03)
= EMF
actual (3.20)
+ (Ia
actual (3.02)
xRa
(3.13)
)
= 390V + (217 A x 0,23 W)
Ua
actual (3.03)
= 440 V
EMF
actual (3.20)
= 390 V
Under no load condition, at full speed:
Ua
actual (3.03)
= EMF
actual (3.20)
+ (Ia
actual (3.02)
x Ra
(3.13)
)
= 390 V + (»0 A x 0,23 W)
Ua
actual (3.03)
= EMF
actual (3.20)
= 390 V
Because of the EMF based controller the drive uses
Automatic Field Weakening as soon as the nomi-
nal EMF is reached to achieve full speed. But that’s
only possible in tacho or encoder controlled mode, in
EMF feedback there is no field weakening.
Example:
Motor name plate
Armature Voltage (Ua) nominal 440 V
Armature Current (Ia) nominal 217 A
Field Voltagel (Uf) nomina 220 V
Field Current (If) nominal 4.6 A
Speed (n) nominal 2250 rpm
Parameter settings
Arm Volt Nom (1.02): ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿé 420 V !
Arm Cur Nom (1.01): 217 A
Field Volt Nom (1.04): 220 V
Field Cur Nom (1.03): 4.6 A
Base Speed (1.05): 2250 rpm
Max Speed (1.06): 2250 rpm
Armature Resistance (3.13) (Ra)
determined by Arm Autotuning: 230 mW
440 V
(
1.02
)
390 V
U
(
V
)
n
(
rpm
)
2250
Ua
act (3.03)
EMF
act (3.20)
Ia x Ra
no load
full load
Deviation of
Ua
depends on
load condition
370 V
U
(
V
)
n
(
rpm
)
2150
Ua
act
(3.03)
EMF
act
(3.20)
Ia x Ra
parameter settin
g
s
motor name plate
Deviation of
Ua
depends on
load condition
420 V
(
1.02
)
440 V
2250
Base Speed (1.05)
Max Speed (1.06)
100% EMF
100% EMF reached.
Start of Automatic
Field Weakening.