ABB ACS800 User Manual page 40

40
Without IR compensation, the motor can only give a very low starting torque at its
nominal current. A typical relation between the starting torque and current is shown
below.
1
The current depends on the demand for starting torque. The magnetizing current of
the motor equals
The torque-producing current equals
Resistive losses consist of transformer, cable and motor stator resistance. Thus, the
voltage drop at the required current equals
where
The voltage drop of the drive output equals
Appendix – Step-up applications
T / T
rated
1
2
ϕ
(
I = 1 cos –
magn
T
ref
ϕ
⋅ (
-------- -
I = cos
torq n
100
⋅ (
U = I R
drop,phase 2 k
2
I = I + I
2 magn torq
U
1
⋅
------
U =
drop,primary
U
2
2
) ⋅
I
n n
) ⋅
I
n
)
+ R + R
c s
2
⋅
3 U
drop,phase
I / I
rated
3