Fuse

It depends on local regulations, among other things.

Capacity of C.B.

Buy a code book!

Take a class!

Ask an electrician!

It all has to do with reaction time and circuit design...

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Control_Transformer_Protection.pdf

How many circuit breakers do you find in your automobile or truck? How many fuses? Does that answer your question to an extent? First of all, the circuit must be designed so the only thing that blows the fuse is a direct source upstream of the load. Second, you need to decide whether you want an instant blow fuse, or a slow-blow fuse (typically a ceramic case, not glass).

It depends upon what's important to you, something which typically you don't share with us, things like; peak let through current, current limiting ability, available short circuit current, resettability, difficulty of replacement, positive fault identification, current vs time characteristics, fast-blow, slow-blow, high rupture capability (HRC), nature of load, resistive, inductive, capacitive, danger/damage to nearby equipment/circuitry, physical space, mechanical/physical/electrical shock resistance, personnel safety, time to restore service, conductor size/type, etc., etc.

To put it succinctly, you need to know what you're doing before you go swapping out components in a circuit.

If you have to ask then the answer is that you should not design a circuit at all. Certainly you can use a circuit that has a circuit breaker or fuse. You are doing that right now.

I will mention that there is a common problem with novices using an AC rated fuse of circuit breaker in a DC (battery) circuit. Due to the continuous zero crossing voltage of an AC circuit the fault current a protection device can stop is much higher than it is for a DC fault. Compounding the problem is that the maximum (fault) current many batteries can create can be orders of magnitude greater than that of a transformer. Ask any car mechanic that accidentally shorted out a car battery with a wrench or now missing piece of hood sheet metal.

True, and us usual ROFLMAO!

I agree with James steward. It depends on the circuit design & whether you can use a slow blow or a quick blow fuse. One has to weigh not the circuit per say, but what device the circuit and fuse protects.

Whether to use a fuse or a CB depends somewhat on the application. In general, fuses are used for short circuit protection, while CBs are used for overload protection. In some applications both may be used.

Circuit breakers have problems with vibration creating nuisance trips,so automobiles seldom use them for this reason,in addition to the increased cost and weight of circuit breakers.

They are also very difficult to seal from the environment.

Imagine a box full of circuit breakers under the hood of a car during a heavy rain,or on a dusty bumpy road.I don't think you would get very far.

CB's also generally respond more slowly to an overload or short circuit,because an internal bi-metallic spring has to heat up to trip the internal mechanism,and this takes time.

A fuse link also takes time to melt,but can have very little mass so can respond faster.

Fuses are lighter,cheaper,and can respond much faster,and so are the choice for sensitive electronics.

There are time-delay fuses,as well as current limiting versions available.

As always,the application will determine the choice.

Basically:Electro-mechanical circuit such as Motors,or lights,heaters that need a basic level of protection, in a relatively clean and vibration free environment,a CB is the device of choice.

For electronic circuitry,the fuse is the default choice.

There are cases where a fuse is used in high voltage or medium voltage applications,and can be seen on power poles.

Some of these huge fuses are used inside of industrial buildings and they are also fitted with an integral muffler.

Be careful to check the AIC of the fuse for DC and AC applications,as well as the fuse rating itself.

Hope this helps.

When working for a battery manufacturing company, I replaced many fuses with MCBs (up to 32A) on battery-charger-cum-regenerative-dischargers. I handled about 12000 such machines as a maintenance head. When a unit is is running in discharge mode and if there is a power failure chances of fuse blowing out is 90%; as all these equipment are SCR based. Another trick I have done is to introduce suitable inductor in discharge path so that current is limited to less than blowing off fuse or MCB to trip.

Just sharing my practical experience.

Be warned that "low voltage" can have different meanings - you may describe 12 volts as low voltage and 230 volts as high voltage, but for example, here, national electrical regulations for buildings define "Low Voltage" as 1000 volts AC/1500V DC or less (normal house supply is 230V 50 Hz), while "Extra Low Voltage" is less than 50 volts AC or 120 volts ripple-free DC.

The basic function of a fuse or circuit breaker is to prevent fire caused by overload or short circuit. Most are designed to protect cables - other equipment has more variable overload/short circuit capacity relative to continuous rated current.

In many cases fuses or circuit breakers can be used, the choice is a matter of cost, size and convenience.

To meet the basic function, either device must, to be interchangeable, have .....

1. The same rated current
2. The same rated voltage
3. The same short-circuit current breaking rating

If ratings 2 & 3 exceed what the supply can deliver, that is OK.

In common domestic 230 VAC use here, an 18 x 90 x 70mm circuit breaker has a breaking capacity of 6000 amps while the 25 mm x 6.3 mm diameter ceramic fuses in each appliance plug have the same breaking capacity.

An important advantage of fuses is that you get a new item every time one blows - most domestic circuit breakers can only break their maximum short-circuit rating ONCE or 3 times according to the specification.

An important advantage of circuit breakers is that you can turn them off while ON LOAD.