Fuses vs. Circuit Breakers

E-T-A Elektrotechnische Apparate GmbH

Comparison

Fuses vs. Circuit Breakers


Part 1: General advantages of CBEs

Part 2: 1610/1170 versus Blade Type Fuses

Comparison Fuses vs. Circuit Breakers






What is a fuse? A fuse is a device that protects against damage from excessive current. It contains a short piece of wire made of an alloy that melts readily. The flow of current through a fuse causes the wire to heat up and melts when excessive current passes through the fuse.

This action burns out the fuse and breaks the circuit. It also interrupts the flow of electricity because a fuse is always connected in series with the circuit it protects. A burned-out fuse which is commonly called a "blown" fuse must be replaced for the circuit to function.



Who invented the fuse?

?


The fuse was invented (and patented) in 1880 by Thomas Alva Edison, the famous inventor of the incandescent light bulb.



Different types of fuses

Blade Type Fuses

Glass Fuses

SMT Fuses

Bolt-In Fuses

Comparison Fuse Types


CBEs: Usable many times

Fuses: Usable once only

Therefore prices cannot be compared on a one circuit breaker/one fuse basis.

ON - OFF ON - OFF .........................ON - OFF ON - OFF

ON - OFF

ON - OFF

ON - OFF

ON - OFF

ON - OFF

ON - OFF

ON - OFF

ComparisonFuses vs. Circuit Breakers


Convenient resetting of CBEs reduces downtime and service repair costs. There is no need of spares.

And: Risk of using temporary inappropriate substitutes is eliminated, warrenty costs are reduced.

Damned! Has anybody seen a spare fuse!



Most CBEs have a status indication.

Fuses don‘t!E-T-A Type 1658

ON OFF



Many types of CBEs are usable as ON/OFF switches

Fuses aren‘t!The E-T-A series 3120 is used to switch

the grain mill ON and OFF, at the same time protecting the electric motors

from overheating by overcurrents.

Example



CBEs: single and multipole versions are available.

Fuses: only single pole versions available..

Some Examples

E-T-A 8340-F, three pole

E-T-A 8345, two pole

E-T-A 3140 three pole



CBEs: No hazard when the circuit breaker is unintentionally switched onto a short circuit.

Fuses: Installing a fuse with the load connected may cause an open intensive arc which is a potential hazard for personnel.

This fuse was plugged in on an existing short circuit. The arc

destroyed the terminal block.



Many CBEs are available with auxiliary contacts.

Fuses aren‘t!

E-T-A 2210-S with two integral auxiliary contacts

Terminals of the auxiliary contacts



CBEs: No shifting of characteristic curves.

Fuses: Ageing may shift the characteristic curves which may cause nuisance tripping (expensive downtime and stoppages)

Time curve of a 10A blade type fuse

(Littlefuse)



CBEs: Well adjusted to the load, even in the event of high inrush currents from capacitors and motors.

Fuses: Trip upon inrush currents; otherwise a higher current rating, possibly requiring a larger wire size, must be used, in which case protection from low overloads is no longer ensured

Diagram of start-up current of an unloaded asynchronous motor

Diagramm: E-T-A Laboratory


Thermal and thermal-magnetic CBEs: Because of its temperature dependent characteristic curve the circuit breaker perfectely adapts to the temperature dependent capability of the load.

Fuses: The characteristic curve is independent from the ambient temperature.


You‘ll find more manufacturers of fuses in our competitor database.

Manufacturers of fuses






Reset button / status indication

Manual release buttonwith colour coding



Test current

A

Operating times

min. max.

1.1 IN 360 000(100h)

1.35 IN 0.75 600

2 IN 0.15 5

3.5 IN 0.04 0.5

6 IN 0.02 0.1

Trip time characteristics

The time characteristics ofthe blade fuse is stipulatedin standard 72581 and ISO 8820.

Thermal circuit breakersshow a delayed responsecompared to fuses.

ISO8820-3



Trip time characteristic

The time/current behaviour of circuit breakers depends on the type.

This is the trip time curveof type 1610.


Data sheet 1610


The trip time behaviour of a circuit breaker depends on the type.

Trip curve comparison of type1610 and blade fuse.

Data sheet 1610 Trip time characteristic



5 10 50 100 500

0.1

1

10

100

1000

10000

0,35

0,5

0,75

1,0

1,5 2,0

2,5

Heat-up time (s) of a cable from 20°C up to max. temperature of 160°C

current (A)

t

Temperature behaviour of automotive cables



5 10 50 100 500

0.1

1

10

100

1000

10000

1,0

Current (A)

t

Trip curve of the 1mm² cable - rated load 10A

Temperature behaviour of automotive cables

Heat-up time (s) of a cable from 20°C up to max. temperature of 160°C



The green line shows the triptime required by a cable with corresponding rating to reach160°C at a certain current.

Both the fuse and the circuit breaker are fast enough.

Data sheet 1610Trip time characteristic



Insensitive to inrush peaks.Overload is switched offreliably.

A smaller rating is possiblewith the same load.

Trip time characteristicsAdvantages of the circuit breaker

t

I(t)



Three ways to find your rating



Circuit breakers allow the useof thinner cables with thesame rated current.

Fuses have to be oversized -and so do the cables.

Less copper through thinner cables



Replace fuses by circuitbreakers with the samecurrent rating

Current peaks are toleratedwith unchanged protection.Circuit breakers do not age.

tin



Disconnection with smallerovercurrent. Fast in the event of a shortcircuit.

Replace fuses by circuitbreakers with smallercurrent rating



Cable characteristics

Cable characteristics


E-T-A Elektrotechnische Apparate GmbH33

CBs areresettable

CBs help to reducecable cross sections

CBs offerenhanced safety

CBs increasethe reliability

Technology

Fuses vs. Circuit Breakers