ABB UNITROL 1020 - Page 65

 Chapter 3 - Device Overview
UNITROL 1020 User Manual 3BHS335648 E82 57
IM Limiter
- Limiting value of the maximum machine current
- Time Multiplier according to IEC 60255-3, Table 1,
Col. B, very inversed characteristic
- Limiter active
Maximum [%]
Time Multiplier K
Maximum Active = True/False
Limiter becomes active after time set by
„very inverse characteristic“
t =
13.5
Im
𝐼
LIM
− 1
∗ 𝐾
3.4.4.2 Limiters Temperature Influence
IM Limiter
T1 at Max IM
T2 at IM th2
T3 at IM th3
T4 at IM th4
Machine current level
Machine current level
T1 [°]
T2 [°]
T3 [°]
T4 [°]
IM th2[%]
IM th3[%]
Machine current IM
Cooling temp.
[°]
25
20 40
100
P1
P2
P3
P4
[%]
T1 T3T2 T4
Im_th2
Im_th3
Max IM
Ie Limiter
T1 at Max continuous Ie
T2 at Ie th2
T3 at Ie th3
T4 at Ie th4
Excitation current level
Excitation current level
T1 [°]
T2 [°]
T3 [°]
T4 [°]
Ie th2 [%]
Ie th3 [%]
Excitation current Ie
Cooling temp.
[°]
25
20 40
100
P1
P2
P3
P4
[%]
T1 T3T2 T4
Ie_th2
Ie_th3
Max.
Continuous Ie
3.4.4.3 Field Voltage Limiter
The measured excitation current is used to estimate the field voltage through a look-up
table, in which the values are linearly interpolated. If the estimated field voltage is larger
than the defined maximum field voltage (Ufmax), the difference is multiplied with the gain
UfLimGain. The resulting value subtracts the maximum excitation current limit Max Ie,
thus reducing the field voltage.
If the gain UfLimGain is set to zero, this limiter is disabled.
-
Ie
Vfd_max
p

0
Ie_Max-Ie_Del
+
Look-up
table
Vfd
error
Gain

Ie_Max
-
+
Ie_Max value –
to Ie_Max limiter