Bypass - Siemens SINAMICS G120 CU230P-2 HVAC Operating Instructions Manual

7.9.13

Bypass

In the bypass function, the motor is either
operated by the inverter or directly on the line.
The bypass control can either be realized
depending on the speed via the inverter or
independently of the speed via a signal from
the inverter or via a higher-level control.
If the bypass is controlled by a higher-level
control, the control must lock the contactors
so they cannot switch on at the same time.
If controlled by inverter, the digital outputs are
used to activate two contactors via which the
motor is powered. The inverter is provided
with contactor position feedback via the digital
inputs. This is evaluated. If using direct
connection logic (high level = ON), both
contactors should be NO contacts.
Note
Flying restart must be activated for the bypass function (p1200 = 1 or 4).
NOTICE
Bypass operation in the essential service mode
The special features for bypass operation in the essential service mode are described in
Section Essential service mode (Page 252).
Changeover operation between line and inverter operation
At changeover to line operation, contactor K1 is opened (after the inverter pulses have been
inhibited). The system then waits for the motor de-excitation time to elapse, after which
contactor K2 is closed, connecting the motor directly to the line supply.
When the motor is switched to the line supply, an equalizing current flows that must be taken
into account when the protective equipment is selected and dimensioned.
Frequency inverters with Control Units CU230P-2 HVAC, CU230P-2 DP, CU230P-2 CAN
Operating Instructions, 01/2011, FW 4.4, A5E02430659B AD
7.9 Application-specific functions
Bypass circuit for control using the inverter
Functions
265