Safety instructions
Thermal motor monitoring
Forced ventilated or naturally ventilated motors
2
33
EDBCSXA064 EN 3.2
2.2.1 Forced ventilated or naturally ventilated motors
Parameter setting
The following codes can be set for I
2
x t monitoring:
Code Meaning Value range Lenze setting
C0066 Display of the I
2
x t load of the motor 0 ... 250 % −
C0120 Threshold: Triggering of error "OC6" 0 ... 120 % 0 %
C0127 Threshold: Triggering of error "OC8" 0 ... 120 % 0 %
C0128 Thermal motor time constant 0.1 ... 50.0 min 5.0 min
C0606 Response to error "OC8" TRIP, warning, off Warning
Calculate release time and I
2
x t load
Formula for release time Information
t +*(t) ln
ȧ
ȧ
ȡ
Ȣ
1 *
z ) 1
ǒ
I
Mot
I
N
Ǔ
2
100
ȧ
ȧ
ȣ
Ȥ
I
Mot
Actual motor current (C0054)
I
r
Rated motor current (C0088)
t Thermal motor time constant (C0128)
z Threshold value in C0120 (OC6) or C0127 (OC8)
Formulae for I
2
x t load Information
L(t) +
ǒ
I
Mot
I
N
Ǔ
2
100%
ǒ
1 * e
*t
t
Ǔ
L(t) Chronological sequence of the I
2
x t load of the motor
(Display: C0066)
I
Mot
Actual motor current (C0054)
Ir Rated motor current (C0088)
t Thermal motor time constant (C0128)
If the controller is inhibited, the I
2
x t load is reduced:
L(t) + L
Start
e
*
t
t
Ǹ
L
Start
I
2
x t load before controller inhibit
If an error is triggered, the value corresponds to the
threshold value set in C0120 (OC6) or
C0127 (OC8).
Read release time in the diagram
Diagram for detecting the release times for a motor with a thermal motor time constant
of 5 minutes (Lenze setting C0128):
I = 3 × I
Mot N
0
50
100
120
0 100 200 300 400 500 600 700 800 900
1000
t [s]
L [%]
I = 2 × I
Mot N
I = 1.5 × I
Mot N
I = 1 × I
Mot N
9300STD105
Fig. 2−1 I
2
× t−monitoring: Release times for different motor currents and trigger thresholds
I
Mot
Actual motor current (C0054)
I
r
Rated motor current (C0088)
LI
2
x t load of the motor (display: C0066)
T Time
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