Mechanical Cell Bypass (U11) - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

Operating the Control
7.4 Cell Bypass
Tool Suite or keypad. No permanent record is kept as to the status of the cell bypass, therefore
if control power is interrupted, the bypass will be reset. Removing MV will also cause the bypass
contactors to open.
Use of the forced bypass feature is intended for testing bypass only. Since the forced "fault" is
software generated and not within the cell, it must be persistent for bypass to work. On reset (or
fast bypass) the cell is bypassed. If the maximum number of cells bypassed is exceeded, a
permanent drive fault is created, and the resest bypassed cells function is prevented from
working (since the drive is continually in cell diagnostics). Control power must be reset to restore
the bypassed cells (control power is removed to replace faulty cells, so this is similar in operation
to the real-world scenario).
Resetting Bypassed Cells
The NXGpro software provides a mechanism to reset bypassed cells to work in conjunction with
the Force Cell Bypass function, if it is used for testing purposes only and no permanent cell fault
exists. This function is labeled "Reset bypassed cells" (ID 2640) and is set to Level 7 security. It
cannot be invoked while the drive is running.
If the number of cells required for operation ("Permitted Min cell count" - ID 2541) is changed,
then the drive must re-initialize cell diagnostics. This automatically resets cells forced into bypass
by this function.
Note
Resetting bypassed cells should not be used for cells that have actually faulted in operation.
7.4.3

Mechanical Cell Bypass (U11)

Mechanical cell bypass protects against the following potential failures:
• Failure of any component in the power circuits
• Failure of any component in the communications circuits
• Power semiconductor failure
The tolerated amount of reduction in capacity will depend on the application but in most cases
a reduction in capacity is preferable to a complete shutdown.
To implement the mechanical cell bypass option, a contactor is added to the output of each cell
as shown in the figure below.
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NXGPro+ Control Manual
Operating Manual, A5E50491925A