Effective 10/2004
Page 11
I.L. 70C1036H05
functions of the Digitrip Trip Unit are performed by its
internal circuitry. There is no mechanical or direct mag-
netic action between the primary current and the mechani-
cal tripping parts of the circuit breaker, thus external
control power is not required for overload or fault current
tripping.
WARNING
IMPROPER POLARITY CONNECTIONS ON THE TRIP
ACTUATOR COIL WILL DEFEAT THE OVERLOAD AND
SHORT CIRCUIT PROTECTION, WHICH COULD RE-
SULT IN PERSONAL INJURY.
OBSERVE POLARITY MARKINGS ON THE TRIP AC-
TUATOR LEADS AND CONNECT THEM PROPERLY
USING THE INSTRUCTIONS PROVIDED.
2.2 Low-Energy Trip Actuator
The mechanical force required to initiate the tripping action
of a Magnum Circuit Breaker is provided by a special low-
energy Trip Actuator. The Trip Actuator is located under the
black molded platform on which the Digitrip unit is sup-
ported. The Trip Actuator contains a permanent magnet
assembly, moving and stationary core assemblies, a
Figure 2.1 Tripping Circuit for a Typical Magnum Circuit Breaker (Partial)
spring and a coil. Nominal coil resistance is 24 ohms and
the black lead is positive. The circuit breaker mechanism
assembly contains a mechanism-actuated reset lever and
a trip lever to actuate the tripping action of the circuit
breaker.
When the Trip Actuator is reset by the operating mecha-
nism, the moving core assembly is held in readiness
against the force of the compressed spring by the perma-
nent magnet. When a tripping action is initiated, the low-
energy Trip Actuator coil receives a tripping pulse from the
Digitrip unit. This pulse overcomes the holding effect of the
permanent magnet, and the moving core is released to
trigger the tripping operation via the trip lever.
2.3 Ground Fault Protection
Only the Digitrip 1150 cat# 11LSIG,11PLSIG and Digitrip
1150
i
cat. # 11IEC-EF,11PIECEF provide ground fault
protection.
2.3.1 General
When the Digitrip 1150 family includes ground fault
protection features, the distribution system characteristics
(for example, system grounding, number of sources,
number and location of ground points, and the like) must
be considered along with the manner and location in which
