Sevcon MillipaK 4QPM - Safe Operating Area (SOA)

Controller Protection Safe Operating Area
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MillipaK 4QPM Controller Manual Page 59 13/08/03
Safe Operating Area (SOA)
The controller’s current may be limited at high and/or low duty cycles depending on its current
and voltage specification. This is to reduce the thermal stress on the power components in order to
increase long term reliability. See Figure 7.
The “Safe Operating Area” is a characteristic of the MOSFETs and Freewheel Diodes which
make up the power-frame. The MOSFET SOA restricts current at high duty cycles on all
configurations, and the Diode SOA tends to restrict the current at lower duty cycles on lower
voltage applications.
For most applications SOA will have little or no effect on the operation of the controller. Its effect
is more significant in protecting the controller against adverse loads such as damaged motors and
static test rigs.
0
10
20
30
40
50
60
70
80
90
100
% of Max. Current
0 20 40 60 80 100
% On
24-48V Controllers
Figure 7: SOA Characteristic