Brochure

PowerPact H-, J-, and L-Frame Circuit Breakers
Glossary
268
02/2016 © 2011–2016 Schneider Electric
All Rights Reserved
main disconnecting contacts = Spring-loaded and self-aligning contact on the rear of a drawout
circuit breaker that provide positive electrical contact when the circuit breaker is in the connected
position.
Masterpact™ = The family of universal power circuit breakers including insulated case circuit breakers
and low-voltage power circuit breakers.
MCH = See spring-charging motor.
MDGF = Modified differential ground-fault system.
manual charging handle = A manually-operated handle which charges the circuit breaker closing springs.
mechanical operation counter (CDM) = A mechanical device which indicates the total number of
circuit breaker operating cycles.
Micrologic™ = The family of electronic trip systems available on molded case circuit breakers,
insulated case circuit breakers and low-voltage power circuit breakers.
miniature circuit breaker (MCB) = A small circuit breaker which is assembled as an integral unit in a
supportive and enclosed housing of insulating material, rated 150 A or less and used in 120 V, 120/240 V,
240 V and 480Y/277 V ac systems and dc systems up to 125 Vdc.
MN = See undervoltage release.
Modbus™ communication network = A communication network comprised of programmable
controller interface units, protocol software and modems.
molded case circuit breaker (MCCB) = A circuit breaker which is assembled as an integral unit in a
supportive and enclosed housing of insulating material, generally 20 to 3000 A in size and used in
systems up to 600 Vac and 500 Vdc.
motor circuit protector = A recognized component of construction similar to a circuit breaker except
with no thermal elements so that it provides short-circuit protection only.
MX = See shunt trip.
National Association of Standardization and Certification for the Electrical Sector = See ANCE.
neutral current transformer = A current transformer which encircles the neutral conductor; required
on circuit breakers with ground-fault protection, when applied on a grounded system.
NMX
®
(Norma Mexicana X) = Listing mark indicating certification to non-mandatory Mexican safety
standards.
NOM = Listing mark indicating certification to mandatory Mexican safety standards
OF = See auxiliary switch.
open/closed indicator = An indicating means which displays the position (open or closed) of the main
contacts.
operating mechanism = An internal mechanical system which opens and closes the circuit breaker
contacts.
OTS = Overcurrent trip switch (alarm switch, bell alarm). A mechanical switch that operates when the
circuit breaker is tripped by the trip system.
overcurrent = Any current in excess of the rated continuous current of equipment or the ampacity of a
conductor.
overcurrent mechanism = An internal mechanical system which trips the circuit breaker during an
overcurrent.
overcurrent trip element = A device which detects an overcurrent and transmits the energy
necessary to open the circuit automatically (UL only).
overcurrent trip switch (SDE) = A mechanically-operated switch which indicates when a circuit
breaker has tripped due to overcurrent conditions.