34
3
Selection and application
3-1 Selection check points
3-1 Selection check points
When applying MCCBs to low-voltage circuits it is necessary
to consider their short-circuit breaking capacities, rated
voltages, rated currents, installation details, protection
systems, wire sizes and type of load (motor, capacitor,
mercury arc lamp, etc.)
Fig. 3-1 illustrates points to be considered when selecting
MCCBs. These are listed in Table 3-1.
3-1-1 MCCB selection check points
(1) Power supply system
s $ISTRIBUTIONSYSTEMTYPE.ETWORK
s 0OWERSUPPLYCAPACITY4RANSFORMERK6!
s 2EGULATION
s!#OR$#
s &REQUENCY
s,INEVOLTAGE2ATEDVOLTAGE
s #IRCUITS3INGLEPHASEPHASE
(2) Location
s %NVIRONMENTCONDITIONS
s !MBIENTTEMPERATURE
(3) Installation and connection
s -OTORCONTROLCENTERDISTRIBUTIONBOARD
s -AINORBRANCH
s &RONTMOUNTEDFRONTCONNECTION
s &RONTMOUNTEDREARCONNECTION
s &LUSHMOUNTED
s0LUGIN
s $RAWOUT
s!RCSPACECLEARANCE
s -OUNTINGANGLE
s4ERMINATION
(4) Applications
s ,INEPROTECTION s-OTORPROTECTION
s )NSTANTANEOUSTRIP
s-ARINEUSE
s 3PECIALPURPOSE7ELDERCAPACITORLIGHTS
(5) Short-circuit breaking capacity
s &ULLYRATED
s3ELECTIVETRIP
s #ASCADEBACKUP TRIP
(6) Short-circuit current
s -##"SERIES
s&RAMESIZE
(7) Loads
s -##"RATEDCURRENT
s7IRESIZEBUSBARS
s #URRENTTIMECHARACTERISTICS
(8) Characteristics
s 7IREANDLOADEQUIPMENT
Mechanical and allowable thermal characteristics
s "REAKER
Breaking characteristics
Operation characteristics
(9) Operation
s 3WITCHINGFREQUENCYOPERATINGDURABILITY
s /PERATIONMETHOD
Remote – manual, motor driven
External operating handle (V and N)
(10) Accessories
s5NDERVOLTAGETRIP
s!UXILIARYSWITCH
s3HUNTTRIP
s!LARMSWITCH
s0ADLOCKING
s4ERMINALCOVER
s-ECHANICALINTERLOCKDEVICE
s%NCLOSURE
Fig. 3-1 Check points for selection
1. Power supply system
Transformer
2. Location
3. Installation and connection
5. Short-circuit breaking capacity
8. MCCB characteristics
9. Operation
10. Accessory
6. Short-circuit current
7. Loads and wires
8. Wire characteristics
8. Equipment characteristics
4. Application
7. Loads
Load