ABB Modures LZ91 - Page 13

A
I
B
The diameter of circular loci
of the pick-up point P is AB.
Fig. 3.3 - Circular underimpedance starting characteristic
The angle 0 is depending on the network conditions. With the aid of computer
calculations D was found to be 2, 30°.
It is possible to change the angle.,C from 90° to 108°, in which case the
characteristic is no longer a circle (see Fig. 3.4).
A
y
1
my
8
Fig. 3.4 - Special characteristic
o( = 90° or 108°
m off-setting factor = XB/XA
y = permissible setting related
to a concentric circle
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