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Protection Of Single-Phase Motors - Siemens 3RB12 Instructions Manual

Solid-state overload relay
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Number of loops n
Rated motor current I
Example
Protection of
single-phase
motors
3ZX1012-0RB12-1AA1
[A]
N
The device setting current I
I
= n x I
e
N
I
= 0.5 A; n = 3; I
N
If single-phase AC motors are to be protected by the
3RB12 solid-state overload relay, phase L must be
looped through the device.
The main circuits must be connected as shown in
Fig. III.
Note
This is only possible if the device has no internal earth
fault detection:
3RB12 46- ...0., -...1.
3RB12 53- ...0., -...1.
3RB12 57- ...0., -...1.
3RB12 62- ...0., -...1.
5
4
0.25 to
0.31 to
0.3
0.41
calculated according to:
e
= 1.5 A
e
Connection
3
2
0.42 to
0.63 to
0.62
1.24
13

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