How to select MCB / MCCB (Part:2)

(C) Application Type:

(9) 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

 11

 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.

(D) Accessories:

(1) Rotary Handle:

11

  • 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:

33

  • Used for Remote Tripping

(3) Alarm contact:

22

  • It gives Tripping Indication when MCCB Trip.
  • It does not give when MCCB is in normal condition (either ON or OFF)

(4) Auxiliary contact:

33

  • It used for remote signaling and control purpose.
  • It is also give ON/OFF indication of MCCB at remote location.

(5) Under Voltage Tripping:

44

  • It used to trip MCCB in under voltage condition (70 to 35% of rated Voltage).

(6) Mechanical Interlocking:

55

  • 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

(8) Motorized operation:

  • MCCB may have option for manual operation or with a motor mechanism for electrically controlled

About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical) from Gujarat University. He has more than 13 years experience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He is Freelancer Programmer of Advance Excel and design useful Excel Sheets of Electrical Engineering as per IS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India" Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

2 Responses to How to select MCB / MCCB (Part:2)

  1. Ashoke Ghosh says:

    Great solution….

  2. Raju says:

    Thank you sir.

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