The following gures illustrate the voltage available from a Perfect Harmony drive for dierent
cell failure examples. The cells, represented by circles, are shown as simple voltage sources.
15 cell drive in which no cells are bypassed
The following gure shows a 15 cell drive with no cells bypassed. 100% of the cells are in use,
and 100% of full 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°.
r
W\S
1
9&%
9%$9$&
&%
$
&
&
&
&
&
$
$
$
$
$
%
%
%
%
%
Figure 7-3 15 Cell Drive Simplied
Drive output with two cells bypassed
When cells are bypassed in one of the drive phases, the output voltage will become imbalanced.
This example shows a 15 cell drive after bypass of two cells in phase A. 87% of the cells are in use
but the output voltage is imbalanced.
r
W\S
1
9&%
9%$9$&
&%
$
&
&
&
&
&
$
$
$
%
%
%
%
%
Figure 7-4 Drive Output with 2 Cells Bypassed
Operating the Control
7.4 Cell Bypass
NXGPro+ Control Manual
186 Operating Manual, A5E50491925A
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