Mechanism Operated Contacts (Moc) - Siemens UL 489 Operating Instructions Manual

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
(1) Fixed-mounted circuit breaker
(2) Cradle
1 3
b a
2 4
S53
(1)
(1) MOC
(2) 4 signaling switches
(3) Driver for connected position
(4) Driver for test position
(5) Warning label

1 3 1 3
b a b a
2 4 2 4
S52
S51
Attention: Four contact
blocks must be installed
(2)
(1)
(2)
1 3
Attention: Four contact
b a
blocks must be installed
for proper operation
2 4
S50
for proper operation
(5) (3)

(4)
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