Effective 2/2/2001
Page 8
I.L. 70C1037H03
Figure 2.1 shows this tripping circuit for a typical Magnum
Breaker. This arrangement provides a very flexible system,
covering a wide range of tripping characteristics described
by the time-current curves referenced in Section 9.2.
The automatic overload and short circuit tripping character-
istics for a specific circuit breaker are determined by
the ratings of the installed current sensors with a matching
rating plug and the selected functional protection settings.
Specific setting instructions are provided in Section 4.
When the functional protection settings are exceeded, the
Digitrip unit supplies a trip signal to the Trip Actuator. As a
result, all tripping operations initiated by the protection
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 breaker, and external control power
is not required.
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.
Figure 2.1 Tripping Circuit for a Typical Magnum Breaker (Partial)
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
supported. The Trip Actuator contains a permanent magnet
assembly, moving and stationary core assemblies, a
spring, and a coil. Nominal coil resistance is 25 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
NOTE:
The Digitrip Model 220 is not available with ground
fault protection. Only the 520 family has ground fault types
available.
