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PowerPact H-, J-, and L-Frame Circuit Breakers
Glossary
270
02/2016 © 2011–2016 Schneider Electric
All Rights Reserved
sensor size = Maximum ampere rating possible for a specific circuit breaker, based on the size of the
current sensor inside the circuit breaker. Sensor size is less than or equal to frame size.
SGR = Source ground return system.
short-circuit delay (STD) = The length of time the circuit breaker will carry a short circuit (current
greater than the short-circuit pickup) before initiating a trip signal.
short-circuit pickup = The current level at which the circuit breaker short-circuit delay function begins
timing.
short-time delay = The length of time the circuit breaker will carry a short circuit (current greater than
the short-time pickup) before initiating a trip signal.
short-time pickup = The current level at which the circuit breaker short-time delay function begins timing.
shunt close (closing coil) (XF) = An accessory which closes the circuit breaker from a remote
location using an external voltage source.
shunt trip (MX) = An accessory which trips the circuit breaker from a remote location using an external
voltage source.
spring-charging handle = A handle located on the front of the circuit breaker used to manually
charge the stored energy mechanism.
spring charging motor = A motor which electrically charges the stored energy closing spring(s).
STD = Short-time delay.
stored energy mechanism (SEM) = A spring mechanism that is compressed or “charged” and then
released or “discharged” to close the circuit breaker.
terminal block = The connections for control wiring.
tg = See ground-fault delay.
thermal imaging = A trip unit function that accurately maps the heating and cooling effects of load
behavior on rated conductors to provide thermal protection without nuisance tripping.
thermal-magnetic circuit breaker = A general purpose term for circuit breakers that use bimetals and
electromagnetic assemblies to provide both thermal and magnetic overcurrent protection.
thermal memory = Provides continuous temperature rise status of the wiring for a period of time both
before and after the device trips. This allows the circuit breaker to respond to a series of overload
conditions which would otherwise go undetected.
t
r
= See long-time delay.
t
sd
= See short-time delay.
two-step stored energy mechanism = See stored energy mechanism.
transformer = A static device with primary winding, connected in series with the conductor (bus)
carrying the current to be measured or controlled within the switchgear.
trip button = See push-to-trip button.
trip curve = A graphical representation of the response of a circuit breaker to current over a period of time.
trip indicator = A module that mounts directly to the circuit breaker trip unit that displays whether the
circuit breaker tripped due to an overload, a short-circuit or a ground-fault condition.
trip indicator reset = A button on the trip indicator module used to reset the trip indicator.
trip system = A system which consists of a Micrologic trip unit and current transformers.
trip unit = A programmable device which measures and times current flowing through the circuit
breaker and initiates a trip signal when appropriate.
UL
®
= See Underwriters Laboratories Inc.