Applications where LV fuses are technically more adapted than LV circuit-breakers?

In low Voltage applications, Circuit Breakers are commonly used. But due to its characteristics some applications still prefer fuses and switches or switch fuse units. Let us se which all applications find it necessary to use switch fuse units preferably over low voltage circuit breakers.

1. Protection of speed drives

2. Protection against short-circuit when CB characteristics are too short

3. Protection of capacitor banks.

4. Protection in DC applications (UPS, PV inverters …)

MCCB

Moulded case CBs are used for high current application

MCCBs are used to protect single equipment with limited protection requirements

The MCCB shown in the picture is a 100A, 3Phase, 690Volts, 25KA , Curve D

MCCBs are equipped with provision for current adjustment for over load protection

MCCB

Air Circuit Breaker

The most commonly used LVCB

Almost all the low voltage switch gears are equipped with ACBs

Has wide range of protections from Over current to under voltage

There are a number of releases available in the breaker

The releases are connected to relays based in the requirement. Say, for under voltage or earth-fault tripping

Arc quenching is done in the air. No special device is used here except provision for arc elongation

Air Circuit Breaker

Miniature Circuit Breakers (MCBs)

• Miniature Circuit Breakers (MCBs) are generally used for low current application
• This a simple circuit breaker that is used to break the circuit in case of over current
• MCBs are most commonly used in protecting equipment like lamps, heaters, air-conditioners, motors and so on
• MCBs work on the principle of thermo-couple action
• When a current higher than the rated current flows through it, the thermocouple is heated up and trips the MCB
• MCBs are specified as for example : 415 V, TPN (Three Pole Neutral), 32A, 10KA(breaking capacity) and C curve
• There are number of types of MCBs viz :
• 1phase,Single pole
• 1phase 2 pole
• 3 phase 3 pole
• 3 phase 4 pole

Miniature Circuit Breaker – Inner view

1.Actuator lever - used to manually trip and reset the circuit breaker.

2.Actuator mechanism - forces the contacts together or apart.

3.Contacts - Allow current when touching and break the current when moved apart.

4.Terminals

5.Bimetallic strip

6.Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.

7.Solenoid

8.Arc divider / extinguisher

CLASSIFICATION OF CIRCUIT BREAKERS

Based on Voltage

• Low - Less than 1kV
• Medium - 1kV to 52kV
• High/Extra High - 52kV to 245kV
• EHV - 245KV to 765kV
• Ultra High - Above 765kV

Based on location

• Indoor
• Outdoor

Based on External design

• Dead tank
• Live tank

Based on Interrupting media

• Air break
• Air blast
• Bulk oil
• Minimum oil
• SF6 gas insulated
• Vacuum

Outdoor high-voltage AC SF6 breaker made in China

Outdoor high-voltage AC SF6 breaker is used to control EHT Power of the range 110 kV.LWA-126/T3150-40 type outdoor high-voltage AC SF6 breaker is porcelain type SF6 breaker, it adopts a self extinguishing interrupter structure,the

interrupter is located in a insulated porcelain housing and the SF6 gas works as the insulation and arc-extinguishing media, also the springmechanism is equipped; this kind of breaker is widely used inhydro powerstation, city network substation and large power stations,where the breaker controls and protects the power transmission line. This China make product is very cheap and worksatisfactory.

Thisoutdoor high-voltage AC SF6 breaker is fromTianshui Changcheng Switchgear Co.,Ltd (CTCS) is alarge-scale professional company in China`s manufacturing field of transmission and distribution switchgear, is a backbone enterprise ofLanzhou Great Wall Electrical Stock Limited Company.The company located in Tianshui CityIt mainly produces 0.4-126KVswitchgears, electrical components and LV switchgears. The products arewidely used in national large-scale power projects and otherlarge/middle industrial projects such as: petrol-chemical,metallurgy,transportation,mine and construction etc.

Read more at http://www.mvvacuumcircuitbreaker.com/pro.asp?id=11

Ultra Rapid circuit breaker

An Electrical Circuit Breaker is a device that makes or breaks an electric supply. An Electrical Circuit Breaker is also equipped with protective devices and operated very fast. The basic components of a CB are fixed contact, moving contacts, arch quenching devices, latching and releasing mechanism, driving mechanism etc.

AnUltra Rapid circuit breaker is faster than the normal Circuit Breaker.

Bus bars coupling onboard merchant vessels, off shore platform, loop networks, where the current and energy are important because of the installed power and HV design not easy. That means an engineer who is limited with LV options can use this UltraRapid circuit breaker to reduce damages to the circuit.

As installed power increases, electrical distribution has to shift from a LV design to a HV design. Indeed, a high short-circuit level can be a threat to the installation and make impossible the selection of low voltage equipments.