Lenze 8200 Frequency inverters - Manual (Page 208)

Configuration
8200SHB0199 7-71
7.7.3 Thermal motor monitoring
7.7.3.1 I 2 x t monitoring
Code Name Possible settings IMPORTANT
Lenze Choice Info
C120 I 2 k t switch-off 0 0 {1 %} 100
Function With the I 2 ¼ t monitoring, self-ventilated three-phase AC motors can be thermally monitored without
using sensors.
Adjustment - Enter an individual load limit for the motor connected.
- If this values is exceeded for a longer period of time, the controller will set the fault OC6 and
switch-off (see chart).
- The current limits C022 and C023 only have an indirect influence on the I 2 ¼ t calculation:
- The settings of C022 and C023 can make the operation with maximum controller load (C056)
impossible.
- When selecting a drive which does not match (output current much higher than rated motor
current):
- Reduce C120 by the factor of the mismatch.
Example:
With C120 = 100 % and a load of C056 = 150 %, the controller switches off after 60 s when
reaching f
d
> 40 Hz, or earlier with f
d
< 40 Hz.
Important - The setting 0 % deactivates the function.
- This monitoring does not provide full motor protection since the calculated motor temperature is
set to ”0” after every mains connection or disconnection. The connected motor can be
overheated, if
- it is already hot but still overloaded,
- the cooling-air stream is interrupted or the air is too hot.
- Full motor protection can be achieved with a PTC thermistor in the motor.
- We recommend the general use of PTC monitoring systems for multi-motor drives.
- To prevent motors with forced ventilation from starting too early, this function can be deactivated.
- If load-adapted motors are to be monitored at a load of < 100 %, C120 must also be reduced
accordingly.
- The operation of the controller with 120 % overload might lead to the activation of the I 2 k t
switch-off, because the setting of C120 > 100 % is not possible.
- Deactivate the I
2 k t switch-off for the operation of the controller at 120 %overload.
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