98 01-6203-01R3, CG Drives & Automation
5.2.11. Device overload monitoring (i*t)
The inverter calculates the i*t utilisation in order to protect itself against thermal
overload. In simple terms: a higher current or an overcurrent that continues for a longer
time causes a higher i*t utilisation.
DANGER!
Uncontrolled motor movements by pulse inhibit.
When the device overload monitoring function is activated, pulse inhibit is set and the motor becomes torqueless. A
load that is connected to motors without a holding brake may therefore cause uncontrolled movements! Without a
load, the motor will coast.
Only operate the inverter under permissible load conditions.
Details
The device overload monitoring function primarily offers protection to the power section.
Indirectly, also other components such as filter chokes, circuit-board conductors, and
terminals are protected against overheating. Short-time overload currents followed by
recovery periods (times of smaller current utilisation) are permissible. The monitoring
function during operation checks whether these conditions are met, taking into
consideration that higher switching frequencies and lower stator frequencies as well as
higher DC voltages cause a greater device utilisation.
• If the device utilisation exceeds the warning threshold set in 0x2D40:002 (default
setting: 95 %), the inverter outputs a warning.
• If the device utilisation exceeds the permanent error threshold 100 %, the inverter is
disabled immediately and any further operation is stopped.
Device overload monitoring enables operation of the inverter under the following load
conditions:
• Continuous current load with up to 100 % rated current.
• 3-minute cycle: 150 % rated current for 60 s, recovery phase 120 s with 75 % rated
current.
• 15-second cycle: 200 % rated current for 3 s, recovery phase 12 s with 75 % rated
current.
Name / value range / [default setting]
Device utilisation (i*t): Warning threshold
0 ... [95] ... 101 %
If the device utilisation exceeds the threshold set, the inverter outputs
a warning.
With the setting 0 % or ≥ 100 %, the warning is deactivated.
(P135.04)
(Device utilisat.: ixt utilisation)
Display of the current device utilisation.
(P135.05)
Device utilisation (i*t): Error response
(Device utilisat.: Error response)
Selection of the response to be executed when the device overload
monitoring function is triggered.
Associated error code:
•
9090 | 0x2382 I*t error
84
Axis information: Rated current
•
Read only: x.xx A
Display of the rated current of the axis.
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