Moulded Case Circuit Breakers
L & T was the first company to introduce 'Moulded case circuit Breakers (MCCBs)' in India. Over the years, it has developed and enhanced the products to growing requirements of market conditions.
L & T MCCBs use latest technologies for circuit interruption under faults. These MCCBs comply with standards IS 13947, IEC 60947 and EN 60947-2 and are certified at independent and approved test authorities.
L & T offers a wide range of MCCBs with current ratings from 0.63A to 1600A in 3-Pole and 4-Pole versions and breaking capacity from 6kA to 100kA. These MCCBs are available with Thermal magnetic as well as with electronic release above 125A in DX range. These MCCBs are available in fixed or draw out versions. They are also available in utilisation category 'A' or 'B'.
L & T MCCBs are complemented with a wide variety of internal and external accessories.
Distribution Feeders Ideally suited for incoming and outgoing feeder circuits on distribution boards.
Transformers Provide effective protection to distribution transformers as outgoing breakers on the LT side.
DG Sets Used for protection and control of diesel generating sets against overloads and short circuits.
APFC Systems Suitable for controlling LT capacitors for power factor corrections.
DC Loads Suitable for both AC as well as DC applications. Hence find application in protecting rectifier panels.
UPS Used for UPS and Electronic equipment protection.
Motors Specially designed MCCBs for Motor back-up protection provide Type-2 co-ordination as per IEC 60947 in conjunction with suitably rated contractors and relays.
Furnaces Suitable for high frequency systems upto 400Hz and can be used for control of high frequency furnaces. Also used in induction furnaces along with semiconductor fuses.
- Operating mechanism is quick-make, quick-break and trip free. It is independent of manual speed of operation. Contacts cannot be teased into position, nor can the breaker be held closed under fault conditions.
- Clear indication of 'ON', 'OFF' and TRIP' position.
- Suitable for both AC and DC applications.
- Terminals suitable for both copper and aluminium terminations.
- "Push to trip" facility to verify healthiness of mechanism.
- Wide range of site fit accessories.
- Low let through energy.
- No load line bias in new range of MCCBs.
- Rotary operating mechanism has door interlock facility with an option of defeating interlock by an authorized person.
- Housing is made of heat resistant insulating material.
- Silver alloy contacts have long electrical life. The mechanism is so designed there is no arcing on the current carrying part of the contact. The strong "wipe action" of the contact system keeps the contact surface clear of oxide films.
L & T's new range of MCCB's can be mounted up to 90°C in any direction.
MCCBs For Motor Back-up Protection
MCCBs are increasingly being used in motor application as a back- up protection device due to following advantages:
Typical Motor Feeder
- Low down time
- Reduced running cost
- No risking of single phasing
- Availability of various accessories
Fuse Monitoring Device
- A typical motor protection scheme comprises a starter contractor and thermal overload relay and a short circuit protective device (SCPD) e.g.MCCB.
- Thermal overload relay provides close protection to the motor against single phasing and moderate overloads like stalling etc. Protection against higher over currents, beyond capability of the starter including short circuit faults is offered by MCCB.
- It is necessary to have proper discrimination between thermal overload relay and SCPD for any effective protection scheme. Type DM MCCBS are hence designed with instantaneous release to ensure proper discrimination.
L & T's range of MCCBs also includes the Fuse Monitoring Device type 'DF', designed to monitor the operation of fuse.
In the motor feeders, where switch disconnector fuse units are used for motor backup protection, there is every possibility of only one of the three fuses blowing due to a fault, resulting in single phasing. This can be avoided by using fuse monitoring device along with switch disconnector fuse units of any fuse ratings refer page 2/79 for connection diagram.