05.05 Function descriptions
SIEMENS AG 6RX1700-0AD76 9-31
SIMOREG DC Master Operating Instructions
9.14 Thermal overload protection of DC motor
(I
2
t monitoring of motor)
The I
2
t monitoring function is parameterized in parameters P100, P113 and P114. If these parameters
are adapted correctly, the motor is protected against overloading (not all-round motor protection).
This monitoring function is disabled in the factory setting of the parameters (P820 i006 = 37).
Adaptation
P114: A time constant T
motor
in minutes for the I
2
t monitoring function must be entered in
parameter P114.
P113, P100: The permissible continuous current of the motor must be defined by parameters P100
and P113.
The permissible continuous current is the product of the calculation P113 * P100.
Warning characteristic / switch-off characteristic
If the motor is loaded constantly, for example, with about 125% of the permissible continuous motor
current, then alarm A037 is triggered after a time constant (P114) has elapsed. If the load is not
reduced, then the drive is shut down when the switch-off characteristic is reached and fault message
F037 displayed.
Warning/switch-off times for other loads can be calculated from the diagram.
Alarm message triggering by motor I
2
t monitoring function
This diagram shows how long it takes for an alarm message to be triggered if, after a long preloading
period (> 5
*
T_th), a new constant load value is injected abruptly.
T_th = P114 .. thermal time constant of motor
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
00,511,522,53
Time / thermal time constant of motor
Load current / permissible continuous current (P100 x P113)
0% preloading
20% preloading
40% preloading
60% preloading
80% preloading
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