CG Drives & Automation,01-5326-01r5 Functional Description 105
Fig. 95 I
2
t function
Fig. 95 shows how the function integrates the square of the
motor current according to the “Mot I
2
t Curr [232]” and
the “Mot I
2
t Time [233]”.
When the selection Trip is set in menu [231] the AC drive
trips if this limit is exceeded.
When the selection Limit is set in menu [231] the AC drive
reduces the torque if the integrated value is 95% or closer to
the limit, so that the limit cannot be exceeded.
Example
In Fig. 95 the thick grey line shows the following example.
• Menu “[232] Mot I
2
t Curr” is set to 100%.
1.2 x 100% = 120%
• Menu “[233] Mot I
2
t Time” is set to 1000 s.
This means that the AC drive will trip or reduce the current
(depending on the setting in menu [231]) after 1000 s if the
current is 1.2 times of 100% nominal motor current.
10
100
1000
10000
100000
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2
t [s]
i / I2t-current
60 s (120%)
120 s (120%)
240 s (120%)
480 s (120%)
1000 s (120%)
Actual output current/ I
2
t-current
NOTE: If it is not possible to reduce the current, the
AC drive will trip after exceeding 110% of the limit.
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