Bypass - Siemens SINAMICS S120 Function Manual

Vector control

6.22 Bypass

6.22 Bypass
Function description
NOTICE
Incorrect synchronization as a result of an incorrect phase sequence
The target frequency r3804 is specified as an absolute value. It does not contain information
about the direction of the rotating field (phase sequence)!
If the phase sequence of the line voltage, which must be synchronized with, does not match
the motor voltage phase sequence, then this results in incorrect synchronization. In the worst-
case scenario, this can mechanically damage the plant or system.
● Ensure that the line voltage phase sequence matches that of the motor voltage. You can
The bypass function controls two contactors via digital outputs of the drive converter and
evaluates the feedback signals of the contactors via digital inputs (e.g. via TM31). The bypass
circuit allows the motor to be operated using the converter or directly on the supply line. The
contactors are activated by the converter. The feedback signals for the contactor positions
have to be returned to the converter.
Features
The "Bypass" function is characterized by the following features:
● Available for vector control
● Available for induction motors without encoder
Restrictions
The following limitations apply to the "Bypass" function:
● Use only when induction motors are used
● Use only for encoderless speed control (p1300 = 20) or U/f control (p1300 = 0 ... 19)
Versions
The bypass circuit can be implemented in two ways:
● Without synchronizing the motor to the line supply
● With synchronizing the motor to the supply
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correct the phase sequence as follows:
– Interchange the two feeder cables at the converter output or at the line contactor.
– Correct the phase sequence of the motor or converter output voltage using p1820 or
p1821.
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions