SIEMENS
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Siemens D 15.1 · 2017
SINAMICS PERFECT HARMONY GH180
Air-Cooled Drives
Introduction
2
■
Design
(continued)
Linked low-voltage cells
In the SINAMICS PERFECT HARMONY GH180 drive, a series of
low-voltage cells
(see graphic "Schematic of a typical power
cell")
are linked together to build the medium-voltage power
output of the drive system. This modular configuration gives the
SINAMICS PERFECT HARMONY GH180 many advantages
when it comes to maintenance, power quality and reliability. It
also provides the basis for one of its most important advantages
– increased availability through the advanced cell bypass op-
tion.
Schematic of a typical power cell
Advanced cell bypass
The SINAMICS PERFECT HARMONY GH180 drive is designed
to withstand failures that conventional drives would not be able
to cope with as redundancy options have been added to the sys-
tem. The cell-based configuration maximizes uptime and simpli-
fies modifications.
Through a bypass control that is completely separate from each
power cell, the SINAMICS PERFECT HARMONY GH180 ensures
that a failed power cell is automatically bypassed in less than
500 ms.
Since the cells in each phase of a SINAMICS PERFECT
HARMONY GH180 are in series, bypassing a cell has no effect
on the output current of the drive, but the output voltage will be
reduced. Usually the required motor voltage is roughly propor-
tional to speed, so that the maximum speed at which the drive
can fulfill the application requirements will also be reduced.
Therefore, it is important to maximize the motor voltage available
after one or more cells have been bypassed. The following
diagrams illustrate the voltage available from a SINAMICS
PERFECT HARMONY GH180 drive, where the cells, represented
by circles, are shown as simple voltage sources. The following
diagram shows a 15-cell drive in which no cells are bypassed.
With 100 % of the cells in use, 100 % of the original voltage is
available. The voltage commands to the three phase groups of
cells will have phase A displaced from phase B by 120°, and
from phase C by 120°.
Simplified diagram of a 15-cell drive
When two cells are bypassed in phase A, the output voltage will
tend to become imbalanced, as illustrated in the diagram below.
Drive output with 2 cells bypassed in phase A
One possible remedy is to bypass an equal number of cells in all
three phases, even though some may not have failed. The fol-
lowing diagram illustrates this approach. Obviously, this method
prevents imbalance but sacrifices possible voltage capability. In
this diagram, 87 % of the cells are functional, but only 60 % are
in use, and only 60 % of full voltage is available.
Drive output re-balanced by bypassing functional cells
T2
T1
1
2
3
Q1
Q3
Q2
Q4
+
+
Power
output
of cell
Transformer
winding
Fiber optic
signals
to and from
master control
G_D015_EN_00010
Local control circuits
Local
control
power
IGBTs Q1-Q4
C4
B4
C5
B3
C2
B2
C1
A1
A2
A3
A4
A5
B1
C5
B5
B
A
N
C
120°
15 cell drive with no
cells bypassed.
100 % of the cells
are in use.
100 % of full voltage
is available.
V
AC
V
BA
V
CB
G_D015_EN_00013
C4
B4
C3
B3
C2
B2
C1
A1
A2
A3
B1
C5
B5
B
A
N
C
120°
15 cell drive after
bypass of 2 cells
in phase A.
87 % of the cells
are in use, but the
output voltage is
available imbalanced.
V
AC
V
BA
V
CB
G_D015_EN_00014
A2
A3
A3
B1
C1
B2
C2
B3
C3
A
B
N
C
120°
15 cell drive after
bypass of 2 cells
in all phases.
Balance is restored.
87% of the cells
are OK, but only
60% are in use.
60% of full voltage
is available.
V
AC
V
BA
V
CB
G_D015_EN_00007
© Siemens AG 2017