5 Motor control (MCTRL)
5.8 Monitoring
106
Lenze · 8400 BaseLine C · Reference manual · DMS 1.6 EN · 01/2014 · TD05
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5.8.3 Brake resistor monitoring (I2xt)
Due to the converted braking power, the brake resistor is thermally stressed and can even be ther-
mally destroyed by excessive braking power.
The monitoring of the I
2
xt utilisation of the controller serves to protect the brake resistor. It acts in
proportion to the converted braking power.
•If the I
2
xt utilisation reaches a permanently set switch-off threshold:
• The error response set in C574
takes place.
•The "OC12: I2xt brake resistor overload
" error message is entered into the logbook.
• If the system is dimensioned correctly, the monitoring mode should not respond.
• If the DC-bus voltage exceeds the overvoltage threshold due to a braking energy that is too high,
the monitoring for overvoltage in the DC bus is activated ("OU: DC-bus overvoltage" error mes-
sage).
Related topics:
Braking operation/braking energy management
( 101)
Danger!
In the Lenze setting ((C574 = "0: No Reaction") the response of the monitoring function
does not stop the braking operation!
In particular for applications such as hoists or applications with a DC-bus connection, it
must be checked if a stopping of the braking operation due to the setting of C574
= "1:
Fault" is permissible.
Stop!
Implement appropriate protective measures against thermal overload of the brake resis-
tor!
Examples:
• Parameterisation of an error response in C574 and evaluation of the parameterised
error message within the application or within the machine control system.
• Interruption of the mains supply by means of the temperature contact at the brake re-
sistor and a simultaneous activation of the mechanical brake.
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