Functions
8.19 Closed-loop Vdc control
Control Units CU240S
Operating Instructions, 11/2006, A5E00766042B AA
8-139
8.19.1 Vdc_max controller
Data
P1240, r0056 bit 14
r1242, P1243
Parameter range:
P1250 – P1254
Warnings: A0502, A0503, A0910, A0911
Faults: F0002
Function chart number: FP4600
Description
A brief regenerative load can be handled using this function (enabled using P1240) without
the inverter being shut down (tripped) with fault message F0002 ("DC link overvoltage"). In
this case, the frequency is controlled (closed-loop) so that the motor doesn't go too far into
regenerative operation.
If the inverter regenerates too much when braking the machine due to a fast ramp-down time
P1121, then the braking ramp/ramp time is automatically extended and the inverter is
operated at the DC link voltage limit r1242 (see figure below). If the DC link again falls below
the threshold r1242, then the Vdc_max controller withdraws the extension of the braking
ramp.
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Figure 8-73 Vdc_max controller
On the other hand, if the Vdc_max controller increases the output frequency (e.g. for a
steady-state regenerative load), then the Vdc_max controller is disabled by an internal
inverter monitoring function and the warning A0910 is output. If the regenerative load
continues, the inverter is protected using fault F0002.
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