Siemens CU240B-2 Original Instructions

Setting functions
8.6 Protection functions
Inverter with CU230P-2 Control Units
Operating Instructions, 11/2013, FW V4.6.6, A5E02430659B AG
265
8.6.5
Limiting the maximum DC link voltage
How does the motor generate overvoltage?
An induction motor operates as a generator if it is driven by the connected load. A generator
converts mechanical power into electrical power. The electrical power flows back into the
inverter and causes V
DC
in the inverter to increase.
Above a critical DC-link voltage both the inverter and the motor will be damaged. Before
harmful voltages occur, the inverter switches off the connected motor with the fault
"DC-link overvoltage".
Protecting the motor and inverter against overvoltage
The Vdc_max control can be used with the PM230, PM240, PM240-2 and PM330 Power
Modules. To the extent the application permits, the Vdc_max control prevents the DC-link
voltage from reaching critical levels. The Vdc_max control increases the ramp-down time of
the motor during braking, so that the motor feeds back only as little power to the inverter as
is covered by the losses in the inverter.
The Vdc_max control is not suitable for applications where the motor is continuously in the
generator mode. This includes, for example, cranes or applications involving braking large
moments of inertia. Further information on inverter braking methods can be found in Section
Braking functions of the converter (Page 273).
There are two different groups of parameters for the Vdc_max control, depending on whether
the motor is being operated with U/f control or vector control.
Parameter for
V/f control
Parameter for
vector control
Description
p1280 = 1 p1240 = 1
Vdc_max control Vdc monitoring configuration
(factory setting: 1)
1: Enable Vdc_max control
r1282 r1242
Vdc_max control activation level
Shows the value of the DC-
link voltage above which the Vdc_max
control is active
p1283 p1243
Vdc_max control dynamic factor
(factory setting: 100%)
Scaling control parameters p1290, p1291 and p1292
p1284 ---
Vdc_max controller time threshold
Setting for the monitoring time of the Vdc_max controller.
p1290
p1250
Vdc_max control proportional gain (factory setting: 1)
p1291 p1251
Vdc_max control integral time
(factory setting p1291: 40 ms,
factory setting p1251: 0 ms)
p1292 p1252
Vdc_max control rate time
(factory setting p1292: 10 ms,
factory setting p1252: 0 ms)

Siemens CU240B-2 Specifications

General

Brand	Siemens
Model	CU240B-2
Category	Inverter
Language	English