13 Years manufacturer Miniature Circuit Breaker FTB1 for Kuwait Manufacturer
Exterior and dimensions
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|Auxiliary contact||Auxiliary contact and alarm contact||Shunt release||Shunt release and auxiliary contact||Under voltage release||Over voltage release||Busbar mounting base||Motor-driven operation|
Under normal condition, the working principle of main thermostic bimetal in FTB1 SMCB is the same to the usual circuit breakers, it is used for overload tripping. when there is a short-circuit on a branch circuit breaker, the magnet core in the main current path would tilt the moving contact away from the fixed contact to break the circuit,thus producing the electric arc, and limiting the short-circuit current effectively.
In the maintime,the short-circuit current flow to the supplementary current path, a selective resistor and a selective bimetal are connected in series of the supplementary curret path, limiting the short-circuit current to a few hundred amps.
When the downstream circuit-breaker has tripped because of a short-circuit, the contact tips reclose automatically through a simple spring-type system,ensuring other unaffected branch circuits continue in operation.If a short-circuit occur between the FTB1 and the downstream circuit-breaker, another bimetal release enables short-time delayed tripping,ensuring the contact tips remain in the open position enabling isolating.
Scope of use
It is primarily used in critical installations,for instance, office buiding, laboratory, theatre, museum, hotel, shopping mall, telecommunication, coal mine and shipping, chemical industry and metallurgy, industrial plants,medical and health care, bank and securities exchange,airport, underground express way, military establishment and similar loads that requires non-interrupted and reliable power supply.
|Test||Tripping characteristic||Conventional non-tripping current||Conventional tripping current||Initial status||Tripping time|
|a b||E E||1.05In||1.2In||Cold statusRight after test 1||≧2h﹤2h|
|Test||Tripping characteristic||Delayed tripping current||short-time delayed tripping current||Initial status||Tripping time|
|c||E||5In||Cold status||0.05s<t<5s(In≦32A) 0.05s<t<10s(In>32A)|
The FTB1 series operates selectively with respect to the combination with MCBs
|MCB(B,C characteristic) FTB1(Characteristic E)|
Note: T represents total selectivity
Exterior and dimensions
What is the significance of mentioning X/R ratio in a Circuit Breaker?
FUNCTION OF CIRCUIT BREAKER
1. To act as switch for normal load conditions
2. To automatically isolate the faulty part
In all types of faults there is a common element and abnormally low-impedance path for the current to flow. Large electrical current produce a lot of heat transfer, which increases the temperature of cables and transformers, etc. These currents also produce high magnetic forces, which can actually bend buses in switchgear. High fault currents cause magnetic forces, proportional by the square of the fault current.
PURPOSE OF SHORT CIRCUIT STUDY
1. Short Circuit study is helpful and to ensure that personnel and
equipment are protected by establishing proper interrupting
ratings of protective devices (circuit breaker and fuses).
2. If fault current exceeds the interrupting rating of the protective
device, the consequences can be devastating.
3. It can be a serious threat to human life and is capable of causing
injury, extensive equipment damage, and costly downtime.
BENEFITS OF SHORT CIRCUIT STUDY
1. Reduces the risk a facility could face and help avoid catastrophic
2. Increases the safety and reliability of the power system and
3. Evaluates the application of protective devices and equipment.
4. Identifies problem areas in the system.
5. Identifies recommended solutions to existing problems.
IMPORTANCE OF X/R RATIO
The X/R ratio is important because it determines the peak asymmetrical fault current.
The asymmetrical fault current can be much larger than the symmetrical fault current.
Largest asymmetrical fault current occurs when a fault happens at a point when the voltage is zero.
Then, the asymmetrical fault current depends only on the X/R ratio, or power factor, and the magnitude of the symmetrical fault current.
MULTIPLICATION FACTOR [M.F]
The multiplying factor is equal to the ratio of the CALCULATED asymmetrical fault current to the asymmetrical fault current at the TEST.
If the calculated X/R ratio at a device is larger than the test X/R ratio of the device, then the calculated symmetrical fault current must be multiplied by the multiplying factor.
SOURCE: www.power studies.com/files/
Importance of X-over-R Ratios
This video provides an application of fraction operations involving determining the horsepower of an motor.