HOW TO SELECT MCB / MCCB
A. Utilization category / Characteristic (B, C, D, K, Z curve):
- Characteristic of Trip curves of MCCB tell about the trip current rating of MCCB.
- MCB will trip instantaneously according to their Tripping Characteristic at 0.1 sec.
- There are various type of MCCB
- Type B MCCB
- Type C MCCB
- Type D MCCB
- Type K MCCB
- Type Z MCCB
Type B MCCB:
- Operating Current: This type of MCB trips between 3 and 5 times rated current (In).
- Operating Time:04 To 13 Sec
- For example a 10A device will trip at 30-50A.
- Application: Domestic applications or light commercial applications where connected loads are primarily lighting fixtures, domestic appliances with mainly restive elements.
- Suitable for: Restive Load application (Lighting , Small Motor)
- Surge Current: The surge current level is relatively low.
- Installation at: At Sub feeder of Distribution Board.
Type C MCCB:
- Operating Current: This type of MCB trips between 5 and 10 times full load current.
- Operating Time:04 To 5 Sec
- Application: commercial or industrial type of applications, fluorescent lighting, motors etc where there could be chances of higher values of short circuit currents in the circuit.
- Suitable for: Inductive Load application (Pumps, Motor, fluorescent lighting.)
- Surge Current: The surge current level is relatively moderate level.
- Installation at: At incoming / Outgoing of Distribution Board.
Type D MCCB:
- Operating Current: This type of MCB trips between 10 and 20 times full load current.
- Operating Time:04 To 3 Sec
- Application: specialty industrial / commercial uses (Transformers or X-ray machines, large winding motors, discharge lighting, large battery charging). Where current inrush can be very high.
- Suitable for: Inductive- Capacitive Load application (Pumps, Motor)
- Surge Current: The surge current level is relatively High
- Installation at: At incoming of Distribution Board / Panels.
Type K MCCB:
- Operating Current: This type of MCB trips between 8 and 12 times full load current.
- Operating Time:04 To 5 Sec
- Application: Suitable for inductive and motor loads with high inrush currents.
- Surge Current: The surge current level is relatively High
- Installation at: At incoming of Distribution Board / Panels.
Type Z MCCB:
- Operating Current: This type of MCB trips between 2 and 3 times full load current.
- Operating Time:04 To 5 Sec
- Application: These types of MCBs are highly sensitive to short circuit and are used for protection of highly sensitive devices such as semiconductor devices.
- Surge Current: The surge current level is relatively too low
- Installation at: At Sub feeder of Distribution Board for IT equipment.
B. Accessories:
(1) Rotary Handle:
- It is used to extend ON/OFF handle of MCCB when Panel Door is closed.
- It is also used to indicate ON/OFF or Trip Position
(2) Shunt Trip:
- Used for Remote Tripping
(3) Alarm contact:
- It gives Tripping Indication when MCCB Trip.
- It does not give when MCCB is in normal condition (either ON or OFF)
(4) Auxiliary contact:
- It used for remote signaling and control purpose.
- It is also give ON/OFF indication of MCCB at remote location.
(5) Under Voltage Tripping:
- It used to trip MCCB in under voltage condition (70 to 35% of rated Voltage).
(6) Mechanical Interlocking:
- It used to mechanical interlock of two MCCB on the same Panel.
(7) Manual / Auto:
- MCCB may have provision for Auto /Manual operation.
- An “auto/manual” switch in front of Panel.
- When set to the “Manual” position, lock out electrical control and when set to “auto”, lock out the manual control; remote indication
