Siemens SINAMICS PERFECT HARMONY GH180 Function Manual page 200

Operating the Control
7.7 Motor Thermal Overload Protection
The following parameters are used with modifications:
• Overload timeout (1150): this parameter is used to determine the scaling of the overload
from the typical curve (1 sec). The setting is ideally set to 60 seconds as the default for this
algorithm so that the OL relay response is mimicked. The curve is based on 150% overload
operation with the overload set to100%.
• Overload (1140): this parameter is used to determine the threshold of the algorithm for the
TOL, above which the drive will eventually trip (based on the curve). For this algorithm, set
it to the level of maximum normal operation, above which the algorithm will trip. The
algorithm is designed to have this parameter set to 100%, and the time set for the Overload
timeout, ideally 60 sec for OL relay response, such that with 150% overload, the drive will trip
in this time.
• Speed Derate Curve (1151 – 1157): this parameter is used to characterize the derating
based on the loss of cooling via an internal (rotor based) cooling fan on the shaft.
• Overload select (1130): this parameter includes two additional pick list items, Legacy TOL
and Legacy TOL with derate. When changing to either mode, the TOL integrator resets to zero.
The following figure shows the typical TOL relay response in the inverse time graph of Motor
Current overload (above 1.0 PU rating of the motor) versus time to trip. This is the response of
a classic TOL relay, based on 150% overload for 1 second (time to trip). The figure is approximate
but representative of the response.
Figure 7-13
For other current levels and time to trip, these can be taken from the table below, with an I
to 1 PU (these are approximate values):
Overload (%)
150
140
130
120
110
100
I Overload = 100%
I timeout = various settings
198
Motor Current Vs. Time to Trip
Time to Trip (sec)
1
1.3
1.8
3.1
7.2
Continuous operation
Operating Manual, A5E50491925A
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