Accessories for MCCB

As we known,Molded Case Circuit Breaker main function is protection device from overload current and short circuit.It also have a several attachment device for additional protection that we can combine with MCCB.

Common accessories used for MCCB such as phase insulation barrier,Shunt trip,Under voltage trip device,rotary handle and change over system.It can provide more protection function that we want add to the application.

Manufactured design for all electrical accessories provide for MCCB are pre wired.It must attach with MCCB and others device recommended from manufacture for efficient and durability to protect the application of system.Below i listed several common accessories for MCCB :-

What is accessories for MCCB?

1) Phase Insulation Barriers

This accessories design for safety purpose when dealing with MCCB.It provide the inter phase barriers to increase the clearance distances between phases to prevent shortage circuit between phase to phase during the operation of the circuit breaker.It can cause a serious damage and injury if it happened.


2) Shunt Trip Device

The function of  Shunt Trip device is to opens the circuit breaker to cut off the power supply when receive electrical signal.To activated the shunt trip function,it must get the signal from CT (current transformer) that we attach together at outgoing busbar.

When the current is over the limit that we set,it send the signal to shunt trip to activated and cut off the supply.Basically it trigger when voltages rise between 70% and 110% of the coil voltage rating.All Shunt Trip devices are factory fitted with a cut-off supply switch.


3) Under Voltage Trip Device

These device basic function is to open the circuit breaker when the power supply drops below 70% of voltage rating.It detected from main coil that receive power supply voltage line.It cut off the main supply to avoid damage for equipment such as sensitive machine and electronic device.

To switch on bacak the power supply we need to closed manually the circuit breaker when the power supply voltage is reach the setting. The Under Voltage Trip device is always energized during normal conditions when supply voltage is stable.


4) Signaling Switch

These device used when we want signal or trigger another device automatically by remote system.Example we can design the control circuit to indicated information to control panel when MCCB was trip.It have two type of contact that we can used such as normally open (N.O.) and normally closed (N.C.) positions.

  • Auxiliary Switch – Provides breaker ON and OFF status information.
  • Alarm Switch – Provides breaker TRIP status information.
  • Auxiliary + Alarm Switch – Provides breaker ON, OFF and TRIP status information.


5) Rotary Handle Function

The rotary handle function allows the user to easily switch the breaker ON of OFF position by a rotating action.The rotary handle mechanism is equipped with a safety device that prevents the panel door from being open when the breaker is in ON position.

A bypass screw is provided for manual intervention when breaker is in ON position.Pad locking facility is available on the rotary handle. The handle can be pad locked when the breaker is in OFF position.It useful for more safety function like tag out and lock out when maintenance jobs.



  1. For automatic changeover as well as for remote operation a “motor” or a “solenoid” too could be fitted.

  2. Ishara Perera says

    I need to Know basic operation of UVT with a explained circuit diagram

  3. Jagdish D Shrirao says

    I heard about this site from my institute & today i have check the site & found it worth to further carrier in electrical engineering & improve ones skill. so i request you to update me about the latest post.I also request you to explain about RMS current in details & harmonics & transient voltage.

  4. Tanmoy Chowdhury says

    could u please explain how to connect the shunt trip coil to an mccb with required circuit diagram? whether the shunt trip coil needs any auxiliary supply voltage as well or just the supply from cbct?

  5. Could you please inform me, is there any device to protect shunt close/trip, under voltage trip coils?

  6. GIRISH says

    how to calculate MCCB,MCB FORMULA

  7. Hi sir …
    am wondering is it the tripping coil is basically a CT or what and the shunt trip coil is it possible to connect it to outside CT reading current for example from another circuit and used its measured value to trip the MCCB .

  8. Is there phase seperators for 32A MCBs

  9. Thank you sir,
    Please provide information about other accessories also.
    1.spreader link
    2.rear termination
    3.plug in

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