Operating instructions

Functions
5.6 Setpoint preparation
CU240S and CU240E Control Units, FW 3.2
106 Operating Instructions, 03/2009, A5E02440075B AA
5.6 Setpoint preparation
Overview of setpoint calculation
The setpoint calculation modifies the speed setpoint, e.g. it limits the setpoint to a maximum
and minimum value and using the ramp-function generator prevents the motor from
executing speed steps.
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Figure 5-8 Setpoint calculation in the inverter
5.6.1 Minimum frequency and maximum frequency
Limiting the speed setpoint
The speed setpoint is limited by both the minimum and maximum frequency.
Minimum frequency
When the motor is switched on, it accelerates to the minimum frequency regardless of the
frequency setpoint. The set parameter value applies to both directions of rotation. In addition
to its limiting role, the minimum frequency can be used as a reference value for various
monitoring functions (e.g. if a motor holding brake is engaged when the minimum frequency
is reached).
Maximum frequency
The frequency setpoint is limited to the maximum frequency in both directions of rotation. A
message is output if the maximum frequency is exceeded.
The maximum frequency also acts as an important reference value for various inverter
functions (e.g. the ramp-function generator).
Table 5- 27 Parameters for minimum and maximum frequency
Parameter Description
P1080 = ... Minimum frequency
P1082 = ... Maximum frequency