Whats the difference between a switch fuse and a fused switch?

Answer 1

A fuse's main purpose is to quickly disconnect a short circuit from the distribution system. A circuit breaker has a twofold function: it trips on a short circuit by utilizing a magnetic sensor device and it also trips on a thermal device which senses a current overload that is higher than its rated current. Both devices are housed inside the breaker case.

Fuse: When the current passing through a fuse exceeds its rated value it physically burns through a thin strip of metal and opens the circuit so current can no longer flow. You have to get a new fuse to restore operation.

Circuit breaker: When a circuit breaker trips it opens a mechanical switch to interrupt the flow of current. You just need to reset the breaker and you are ready to go again.

In both cases you must always be sure to remove the cause of the over-current situation because, if you don't do that, the effects of a blown fuse or a tripped breaker will continue!

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Fuses and circuit breakers were invented to protect electrical items from being damaged by taking too much current (amps), something which is also known as an over-current fault condition.

FusesHow a fuse works

When an over-current fault condition occurs, which is the same as saying the current gets bigger than the fuse can carry, its internal "fuse wire" gets so hot that it melts and breaks apart, which cuts off the supply of current. When that happens the fuse is said to have "blown".

After whatever caused the over-current fault condition in the circuit has been repaired, a blown fuse must either be replaced with a new one or, if it is the type of fuse which can be rewired, it must be repaired using the correct size of special "fuse wire".

A new fuse should then remain in place un-blown until another over-current fault condition occurs in the circuit it is protecting, which would then cause the new fuse to blow.

What are the advantages and disadvantages of fuses?

To give the same over-current protection, fuses are generally cheaper to make and smaller in size than circuit breakers.

However an ordinary fuse cannot blow as quickly as a circuit breaker can "trip".

Some equipment may require special "quick-blow" fuses so that damage can be prevented when an over-current fault condition occurs. Quick-blow fuses cost much more to make than ordinary fuses but must sometimes be used where a circuit breaker would be too expensive and/or too large in size.

Further notes about fuses:

• Some fuses are rewireable, meaning they can be repaired if they blow. This must only be done using new fuse wire of the correct size. It is dangerous to use fuse wire which is thicker than the size marked on the rewireable fuse's body.
• Other fuses, known as "one-time" or "cartridge" fuses, cannot be repaired when they blow. If that happens they must be thrown away and replaced by a new fuse of the correct size.

  Some one-time fuses look like small cylinders with a metal cap at each end; others look like a small cylinder with a metal screw-cap on one end like a light bulb. One-time fuses for vehicles, known as "fuse-links", have small bodies made of plastic and two metal blades which push into fuse slots in the vehicle's fuse box.

  If a one-time fuse blows it should only be replaced by a new one of the correct size (Amps) for the circuit. The ones which screw in have different sized screw-caps for each size of fuse, with matching sockets to ensure that only a fuse which is the correct size can be screwed into the fuse holder. Similarly, fuse-links have different sized metal blades and matching slots to ensure that a given slot can only accept the correct size of fuse link.

Circuit breakersHow a circuit breaker works

When an over-current fault condition occurs, which is the same as saying the current gets bigger than the circuit breaker was designed to carry, it's mechanism causes its switch contacts to open, which cuts off the supply of current. When that happens the circuit breaker is said to "trip".

When whatever fault condition in the protected circuit has been repaired, the circuit breaker can be "Reset" by pressing a button to close its switch contacts. The contacts should then remain closed until another over-current fault condition occurs in the circuit it is protecting, which would cause the breaker to trip again.

What are the advantages and disadvantages of circuit breakers?

To give the same over-current protection, circuit breakers can be designed to trip much faster than an ordinary fuse but they are generally larger in size and cost more to make.

However circuit breakers are re-usable and can easily be reset after they have tripped - provided, of course, that the fault condition in the protected circuit has been repaired.

A fuse is a protective device that destructively opens when the current flow exceeds a preset value. It is usually designed as a low value resistor that heats up and melts at the specified current value. Once the fuse blows, it must be replaced.

A circuit breaker is a protective device than non-destructively opens when the current flow exceeds a preset value. It is usually designed as a tripping relay/switch that can be reset and reclosed when the fault is cleared.

In both cases, the design can provide for different preset values as a function of time. It depends on whether the intended load pulls a larger startup current than when it runs, such as a motor, which can easily pull four times their run current when they startup. The protective device is selected for the specific type of load, and for the rating of the conductors supplying it.

Answer 2

A "fused switch" is a switch in series with a fuse in a single housing. The fuse and the switch are essentially separate. A "switched fuse" is switch containing a fuse, usually mounted in a carrier and the fuse (and carrier) physically move when switching occurs. <><><> A "fused switch" is a switch which has a fuse to protect whatever appliance the switch is controlling. A "switch fuse" is a fuse that goes into a fused switch!

Answer 3

I believe that an isolator should only be used to isolate supplies that are not under load, while a switch fuse can isolate the supply that the fuse protects.

A fused switch can isolate a three phase supply where a switch fuse might not in fault conditions.This is because three phase faults can occur with only one phase going down and larger currents occurring ??

ian malone.

Answer 4

A switch is a device which can either make or break the flow of current in a circuit, as often as needed, that's all.

A fuse is a device which will allow current to flow in a circuit up to a pre-determined maximum amperage, after which it "melts" to stop the flow, but - unlike a circuit breaker, which can be reset - a fuse can only break the flow of current in a circuit once.

Answer 5

A fuse box has those round things you screw into a socket that looks a lot like a light bulb socket and you have to replace the fuse when it is blown. A circuit breaker is one of those things that has a lever on it that you can reset when it blows and you do not have to replace it. Fuses are old technology and circuit breakers are new technology and can incorporate such features as GFCI and AFCI.

Answer 6

A circuit breaker protect by circuit by not letting the circuit conductors to become overloaded by removing the voltage from the circuit. A switch just opens the circuit but does not provide circuit protection.

Answer 7

A switch is active. You turn it on or turn it off at will. A circuit breaker is passive. It "trips" (activates) if necessary when it's amperage rating is exceeded.

Answer 8

A fuse must be replaced if blown, a circuit breaker can be reset.

Answer 9

It is an isolation device with fuse links.