This would typically be seen in older residential installations where the service was of such a high amperage that the mains required larger breakers than were available (for that panel). Placing two breakers in parallel allowing sharing of the load. Two breakers per (split) phase would total four breakers.
Two breakers of 50 amp rating each (in parallel) provide (generally) 100 amps of protection. Two sets of two would provide mains protection for a 200 amp service.
SF6 circuit breaker
Copper, Brass and Aluminum.
fuses or circuit breakers
Yes, different amperage rating circuit breakers can have the same short circuit characteristics.
Vacuum circuit breaker is used in railway applications and as it is used in the applications where current chopping phenomenon is more
3 pole circuit breakers are used for 3 phase lines
Certainly not in the case of high-voltage circuit breakers. Probably not in low-voltage circuit breakers, as copper is a better conductor and has a higher melting point.
Circuit breakers.
SF6 circuit breaker
Circuit breakers prevent excessive current from flowing in the circuit by "tripping" when the current exceeds the circuit breaker rating. This causes the current to be cut off, and is used to protect the wiring as well as the appliances.
fuses
No, not all circuit breakers are automatically reset. Some circuit breakers need to be manually reset by flipping the switch back to the "on" position after they have tripped. Automatic reset circuit breakers are typically used in specific applications where it is important for the circuit to be quickly restored without human intervention.
The same name breakers as the manufacture of the load center.
Copper, Brass and Aluminum.
Fuses & circuit breakers.
Square D circuit breakers can be purchased from various homeware and DIY stores such as Home Depot or Lowes. Websites that specialise in circuit breakers such as Circuit Breaker Service or All Breakers do sell them as well.
GE circuit breakers with catalog numbers ranging from THQL1115 through to THQL1150 can be substituted like for like with Cutler-Hammer circuit breakers coded CL115 through to CL150, ITE Siemens circuit breakers coded Q115 through to Q150 and Square D circuit breakers coded HOM115 through to HOM150. These are single pole breakers. GE circuit breakers with catalog codes from THQL2115 through to THQL2150 can be substituted with Cutler-Hammer circuit breakers CL215 through to CL250, Square D circuit breakers HOM215 through to HOM250 and ITE Siemens circuit breakers Q215 through to Q250 of the same amperage and voltage. These are double pole breakers.