Safety instructions
Thermal motor monitoring
2
110
EDK82EV903 DE/EN/FR 5.1
2.3 Thermal motor monitoring
Description
With the I
2
t monitoring you can monitor self−ventilated three−phase AC motors thermally
without sensors.
Note!
ƒ The I
2
xt monitoring is based on a mathematical model which calculates a
thermal motor utilisation from the motor currents measured.
ƒ However, the I
2
xt monitoring is no full motor protection, since other
influences on the motor utilisation cannot be detected, like changed cooling
conditions (e.g. cooling air flow interrupted or too warm).
ƒ You can only obtain full motor protection if the motor is equipped with a
PTC thermistor or a thermal contact.
Warnings!
If you use the I
2
xt function in UL−approved systems for thermal motor
monitoring:
ƒ The I
2
xt function is UL−approved.
ƒ In UL−approved systems no additional protective measures for the motor are
required.
For devices from software version V3.9 (nameplate data: E82xV... xx 39), an
additional setting is required!
ƒ Activate the starting value 50% for the I
2
xt function:
– Add 128 to the value displayed in Code C0311.
ƒ Example:
– C0311 = 1 (Lenze setting)
– Setting for UL−approved systems: C0311 = 129
Codes for parameter setting
Code Possible settings IMPORTANT
No. Name Lenze Selection
C0120 I
2
t switch−off 0 0
= inactive
{1 %} 200 Reference: apparent motor current
(C0054)
Reference to active motor current
(C0056) possible, see C0310
C0311*
Functions for
special
applications 2
1
0 All functions switched off A combination of functions can be
activated by entering the sum of the
selection values.
1, 2, 4,
8, 16
System manual
(from software
version 3.9)
1 128
Motor overload (I
2
xt) tart value
Function active: Function switched−off:
When the device is connected to the
mains, the thermal motor load is initialised
with 50 %.
The function has to be activated for
operation in UL−approved systems.
When the device is connected to the
mains, the thermal motor load is
initialised with 0 % ("cold engine")
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