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circuit breaker vs fuse 11
- Thread starter cgossett
- Start date
Jbartos: sure still there are but they are very old (about 30y ago).
New techniques use double interruption:
1. Rotation of two contacts
2. Two parallel contacts in a fork position
3. Two serial contacts in a standard execution
Few producers have them.
Each of them have advantages and disadvantages, still 2. is best since it limits current peak but still allows good seletivity at low SC levels.
The dynamic forces allow them all to open, depending on the CB and the SC, in 3 to 5 msec, like if they felt the raise of current as derivators. Current limiting is defined by UL, if I remember, but not by IEC therefore they are called I2t limiting.
If you argue that fuses will blow even quicklier, I agree with you. If you argue that selectivity with CBs is easier done, too.
New techniques use double interruption:
1. Rotation of two contacts
2. Two parallel contacts in a fork position
3. Two serial contacts in a standard execution
Few producers have them.
Each of them have advantages and disadvantages, still 2. is best since it limits current peak but still allows good seletivity at low SC levels.
The dynamic forces allow them all to open, depending on the CB and the SC, in 3 to 5 msec, like if they felt the raise of current as derivators. Current limiting is defined by UL, if I remember, but not by IEC therefore they are called I2t limiting.
If you argue that fuses will blow even quicklier, I agree with you. If you argue that selectivity with CBs is easier done, too.
Great thread all. It made me recall my early days in this industry when Bussman came around trying to convince us that fuses were the only safe way to go by showing us slow motion movies of exploding circuit breakers. Fascinating stuff, I wish I could get my hands on them now.
I for one am convinced of the technical superiority of fuses as a means of circuit protection, but I must admit that years of field proctice has me specifying circuit breakers. I have been at too many remote sites and found short pieces of pipe inserted into fuse clips because of unavailability of fuses. The prospect of choosing between an expensive potential fire and an expensive proven loss of operation has too many decisions being made by unqualified idiots or well meaning but desperate electricians. Just an opinion carved out of empirical wood. Subvert the dominant paradigm... Think first, then act!
I for one am convinced of the technical superiority of fuses as a means of circuit protection, but I must admit that years of field proctice has me specifying circuit breakers. I have been at too many remote sites and found short pieces of pipe inserted into fuse clips because of unavailability of fuses. The prospect of choosing between an expensive potential fire and an expensive proven loss of operation has too many decisions being made by unqualified idiots or well meaning but desperate electricians. Just an opinion carved out of empirical wood. Subvert the dominant paradigm... Think first, then act!
jbartos
Electrical
- Jan 15, 2000
- 6,440
Suggestion: The dilemma between circuit breakers and fuses needs to be assessed on the case-by-case basis. One subtle thing about fuses, what the circuit breaker may or may not have, is the fuses refillable filaments that may have very refined ratings without a need for changing the fuse block and in case of circuit breaker without changing and ordering different circuit breaker rating, which may or may not have short lead time. The fuses can get very practical in some applications.
Jbartos: me too but none due to contact welding!
99% of the causes of a fault in a CB make it so that the CB will not operate even before being installed, thus making it sure that if you install it and it works, it works ok.
Another topic could be an electronic release where you can have a meta-fault... but producers deny the problem as non existing...
99% of the causes of a fault in a CB make it so that the CB will not operate even before being installed, thus making it sure that if you install it and it works, it works ok.
Another topic could be an electronic release where you can have a meta-fault... but producers deny the problem as non existing...
scud27
I noticed that you are involved in making brakers your bias is showing.
please let me know where to send the next braker I find with contacts welded closed
In my 30 years in the industry I have run into hundreds with considerable damage form their failure. Remember even a bad fuse will open, a braker is always questionable which one do you want bet your life on. Just so you know I do specify and use both all the time each have their place. But the bets protection is always a fuse
I noticed that you are involved in making brakers your bias is showing.
please let me know where to send the next braker I find with contacts welded closed
In my 30 years in the industry I have run into hundreds with considerable damage form their failure. Remember even a bad fuse will open, a braker is always questionable which one do you want bet your life on. Just so you know I do specify and use both all the time each have their place. But the bets protection is always a fuse
jbartos
Electrical
- Jan 15, 2000
- 6,440
Comment: Lately, I have seen many projects that have "all circuit breakers" protection. I think if any Client prefers the circuit breakers, there are enough resources to pay for any potential circuit breaker drawbacks. Analogously, if there is money for a luxurious car, there will always be money for its repairs no matter how costly they are.
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