Current Limit And Overload Operation - Siemens MICROMASTER 411 Operating Instructions Manual

10 Engineering Information
10.1

Current Limit and Overload Operation

The inverter will always protect itself, the motor and the system from possible
damage. Where a short circuit exists on the output of the inverter, the unit will trip
almost instantaneously to protect itself. In the event of short and/or long term
overload conditions, current limit protection now operates rapidly to reduce inverter
current and prevent a trip occurring.
Electronic Trip
This is a very fast current limit, which operates if there is a short circuit (line to line
or most of line to earth faults) on the output. It is a fixed level trip and operates
within a few microseconds.
Overload Limit
This is a very fast limit, which operates within a few microseconds and removes
some of the output pulses to limit the current and protect the inverter. If this pulse
dropping occurs during overload, the operating condition will usually recover and
the motor will continue to run without tripping.
Long Term Overload Limit
This is a slower limit which allows an overload of at least 60 seconds where the
current lies above the motor limit but below the Electronic Trip and Overload Limit.
Continuous Limit
This is the level set as the maximum continuous motor current. The inverter will
control the current to this level after other overloads have timed out.
Figure 10-1 illustrates the interaction of parameters associated with current limit.
Read Only parameters r0027, r0034, r0037 and r0067 help with fault diagnosis.
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MICROMASTER 411 & COMBIMASTER 411
Issue 03/01
Operating Instructions
6SE6400-5CA00-0BP0