Most circuit breakers are spring loaded. In the case of larger circuit breakers you need more stored energy to disengage the heavier contacts than you can achieve in the stroke of the breaker switch. To scale up the design of the smaller breakers, the tab which you push to turn on the breaker would have to be much larger (maybe 10 to 20 cm). In turn, that larger tab could be inhibited from movement unless the entire thing was recessed.

It's all about mechanical advantage to achieve the disconnect.

There are two sets of springs in breakers. One set to open the contacts and another set to close them. The "close set" of springs is compressed to a higher energy level then the "open set" of springs.

Closing the breaker, releases the energy stored in the "close set" of springs and the contacts close and latch. When the breaker closes, the mechanical linkage in the breaker charges the set of springs that open the contacts.

The energy that must be stored in the "close" set must be provided by something. A motor or your arm...

All breakers, even the smallest, have spring charged mechanisms. The reason is as follows: As you begin to close electrical contacts, the dielectric (insulating) properties of the air that separates them goes down with proximity. So as the contacts get closer, the electric current will jump the gap (think of a spark plug). If you do it too slowly, the surface material in the contacts will heat up too much, melt and vaporize. The same holds true for opening the contacts; if you open them too slowly, the arc formed by the separation will vaporize the contacts. So to ensure that the speed, skill and strength of the human operator has no bearing, the breaker is designed with a spring actuated mechanism that move the contacts together, or apart, at a predictable speed, calibrated for the current that the device is intended to carry.

In addition as the current goes up, the electro-magnetic forces caused by the current flow (look up Ampere's Law) will increase and try to force the contacts apart. You therefore need a strong mechanical force keeping them together, but one that can be released in an emergency and not relying on any other power source. Springs do that for you.

I believe the question ius about "charging" only.

The reason why some circuit breakers have "spring charging" is because they are usually quite large (>1000 amps). It is quite typical to find CB's from 2000 amps & higher, to have springs that will close the circuit breaker. The reason for this is that you would need to be very strong (Hercules) to close the breaker if it didn't have this mechanism. Usually, these "spring mechanisms" are charged by;

1] pumping a lever by hand until the spring is fully "charged" (compressed).

2] a small electric motor.

But even the smallest of breakers have a spring charging mechanism, it's just a lot simler to accomplish when the sring doesn't need to be so big. That was my point.

I don't think the OP is talking about small circuit breakers since he mentioned "spring charging". For small circuit breakers, I believe the question would be, "Why are springs necessary in a circuit breaker?"

The act of charging a spring is unique to large circuit breakers. Look at the indicating flag on a large CB - the flag will say either "charged" or "discharged".

Caviat: I'm assuming the OP didn't make any mistake(s) in the original question.

Hi

we are using the vacuum circuit breakers of following name plate details

Make :English Electric company

voltage :12 KV

Rated current :1250A

Making current :25KA

S.C.Current :25 KA/3 sec

In this breaker,they are using only one spring and two coils one for closing and another for tripping .These coils pushes the lever which will close and open the breaker.

Which category this mechanism belongs.How this works.Please share your views.

Regards

gova

Old power circuit breaker designs (GE Magna-Blast, for example) used a very large solenoid to close the breaker, and springs to trip it. Modern power circuit breakers use some type of stored energy, to allow operation of the breaker during a power outage. Oil-insulated breakers use hydraulics or pneumatics because of the power required to move contacts through the viscous oil. As air and vacuum-insulated breakers came into use, spring-powered systems became the standard because they can't leak and have very few moving parts. Medium voltage vacuum breakers usually have 2 separate springs: 1 for closing and 1 for tripping. The trip spring is sometimes inside the close spring, making it seem as if there is only 1 spring. In a few designs, a single spring is divided in function, with approximately 2/3 used for closing and 1/3 for tripping.

A motor is used to charge (compress) the close spring. A hook latch keeps the spring charged after the motor stops. When the close command is given, the close coil releases the hook latch, allowing the spring to quickly force the main contacts together. At the same time, the movement of the mechanism compresses the trip spring (the close spring is stronger, and can compress the trip spring). A separate hook latch holds the trip spring charged. Once the breaker is closed, the charging motor re-compresses the close spring to be ready for the next closing operation. A trip command will cause the trip coil to release the hook latch on the trip spring, forcing the contacts open.

I suspect your breaker is several decades old, as the English Electric brand disappeared around 1970. However, the mechanism design has not changed much in 50 years. ABB, Siemens, Square D, General Electric and others still produce similar mechanisms. Manuals available on their websites should provide much insight into the operation and maintenance of your breaker.

Dear sir

Sorry sir.The make of VCB is General Electric Co.of India Ltd.

Manufactured on 1993

Regards

gova