12 – 7
12.8 Mechanism Operated Contacts (MOC)
The circuit breaker may be equipped with an external auxiliary switch assembly. These external auxiliary switches are known as
Mechanism Operated Contacts. In short, the assembly is also referred to as the MOC.
The MOC assembly is mounted within the circuit breaker compartment (cradle) and is connected to the main breaker-driveshaft
via a coupler, which is added to the circuit breaker during the MOC installation.
The circuit breaker, itself, may be optionally ordered with either no internal auxiliary switches, a set of four internal auxiliary
switches (2 a + 2 b contacts), or eight internal auxiliary switches (4 a + 4 b contacts).
With the addition of a MOC device, an additional eight auxiliary switches (4 a + 4 b contacts) may be added to a circuit breaker.
Note referencing ANSI C37.100:
“a” contact: A secondary contact that is open when the circuit breaker is open, and closed when the circuit breaker is closed
“b” contact: A secondary contact that is closed when the circuit breaker is open, and open when the circuit breaker is closed
Cradle
(1) MOC
(2) 4 signaling switches
(3) Driver for connected position
(4) Driver for test position
(5) Warning label
S50
S51
S52S53
a
3
4
b
1
2
a
3
4
b
1
2
a
3
4
b
1
2
a
3
4
b
1
2
Attention: Four contact
blocks must be installed
for proper operation
Attention: Four contact
blocks must be installed
for proper operation
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