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What Are the Two Major Types of Fuses?

Author: Apogeeweb Date: 19 Jan 2021  210

what are fuses made of

Introduction

In electronics and electrical circuit, a fuse is an electrical safety device that operates to provide overcurrent protection. In order to stop the damaging effects of overcurrent, when too much current flows through the low resistance element of the fuse, the element melts and breaks the circuit, because a special feature of the fuse is that it contains a piece of wire that melts easily. Fuses are widely used for protection of electric motor circuits with different types. Before you read the following note, you can think about a question: what are the types of fuses and its uses?

What is an Electric Fuse? and How to Prevent Short Circuit with Fuses?

Catalog

Introduction

Ⅰ Fuse Basic Overview

1.1 Electrical Fuses Definition

1.2 Fuse Working Principle

1.3 Electrical Fuse Symbol

1.4 Fuse Materials

Ⅱ Electric Fuse Classification

2.1 DC Fuses Basic

2.2 AC Fuses Basic

Ⅲ Conclusion


Ⅰ Fuse Basic Overview

1.1 Electrical Fuses Definition

An electric fuse is a protection device built around a conductive strip that is designed to melt and separate in the event of excessive current. In other words, The fuse breaks the circuit if a fault in an appliance causes too much current to flow. Except that, fuses are essentially temperature-sensitive devices. Even small variations from the controlled test conditions can greatly affect the predicted life of a fuse.

1.2 Fuse Working Principle

The primary task of a fuse is to split the circuit if the circuit draws a current higher than desired, thus avoiding the harm due to short circuits.
The simplest fuse type consists of a resistive part, carefully chosen for its melting point. A slight voltage drop (small enough so that the circuit downstream will not be impacted) is generated across the element when a current passes through this element, and some power is dissipated as heat. Thus, the element's temperature increases. This temperature rise is not necessary for normal currents to melt the filament. However, the melting point is easily reached if the current draw reaches the nominal current of the fuse. The resistive part melts and is disrupted by the circuit. The nominal current is determined by the thickness and length of the resistive material.
To provide predictable trip currents, fuse components are made of zinc, copper, silver, aluminum, or other alloys. Over time, the element must not oxidize or corrode.

1.3 Electrical Fuse Symbol

What is the symbol of fuse? different fuse symbols in the electrical circuit diagram showed below.

fuse symbols

Electronic Symbols of Fuse

1.4 Fuse Materials

The material used for making fuse elements has a low melting point such as tin, lead, or zinc. A low melting point is, however, available with a high specific resistance metal shown in the table below. The material mainly used for fuse elements are tin, lead, silver, copper, zinc, aluminum, and an alloy of lead and tin.

 

Ⅱ Electric Fuse Classification

After you know what is a fuse in a circuit, the following are the types of fuses. There is a wide selection of PCB fuses in the market. Here introduce two major types: AC fuses, and DC fuses. The following note describes different types of fuses and their constriction, working characteristics.

2.1 DC Fuses Basic

  • Cartridge Fuses

This is the fused form that is the most common. In a glass envelope that is terminated by metal caps, the fuse part is encased. In a suitable holder, the fuse is mounted. As the glass envelope is transparent, whether the fuse is blown, it is easy to visually determine.
This style has many versions, including the slow blow fuse and the quick blow fuse. Slow blow fuses have a larger element that can handle overcurrent and are unaffected by spikes in the appliance for a relatively short period of time. Quick blow fuses respond to existing spikes instantly.
To withstand elevated temperatures, some versions of this fuse are encased in ceramic. Sand or oil is packed with fuses for high voltage applications. This is to stop arcing after it has blown between the two ends of the fuse. For direct PCB mounting, SMD variants of cartridge fuses also exist.

 

  • Automotive, Blade Type & Bolted Type Fuses

These fuses are designed especially for automotive systems running up to 32V and 42V at times. They come in the form of a 'sword' (a transparent plastic envelope with flat contacts) and are color-coded according to the nominal current. In other high-power circuits, some of these types are also used.

 

  • Resettable Fuses/Polyfuse

These fuses are self-resetting, much as their name suggests. They contain black particles of carbon embedded inside organic polymers. The carbon black usually renders the mixture conductive. Heat, which expands the organic polymer, is created when a large current flows. The black particles of carbon are pulled apart, and conductivity decreases to the point that there is no flow of current. As temperatures decrease, conductivity is restored. The fuse does not, however, have to be replaced physically. This type of fuse is often referred to as a PTC, which means a positive temperature coefficient since the temperature rises with resistance.
For computer power supplies and phone chargers, the PTC Fuse is ubiquitous. They are particularly handy here because it is difficult to replace them. They are used in aerospace devices for the same purpose.
In their through-hole variants, PTCs are easily recognized by their yellow-orange colour and disc (and sometimes rectangular) form. With white markings, SMD poly fuses normally come in green or with gold markings in black. Virtually every current rating offers PTCs.

 

  • Semiconductor Fuses

With current flow, the power dissipated by a semiconductor increases exponentially, and semiconductors are thus used for ultrafast fuses. These fuses are commonly used to secure devices that are susceptible to even minor current spikes from semiconductor switching.

 

  • Overvoltage Suppression Fuses

Voltage spikes may also often be dangerous to circuits, and with a fuse, an overvoltage safety system is also used to protect against both voltage and current spikes.
There are NTCs (negative coefficient of temperature) put in parallel with the supply. NTC Fuses minimize resistance due to higher current flow and absorb spikes when the supply voltage spikes.
Semiconductor-like devices that bidirectionally absorb voltage spikes are metal oxide varistors (MOVs). Using the linked post, you can learn more about MOV and its work.

types of fuses

2.2 AC Fuses Basic

  • High Voltage Fuses

In high voltage AC transmission lines, these fuses are used where voltages can exceed several hundred kilovolts.
1)HRC (High Rupture Current) Fuses
HRC fuses are fuses of a cartridge type consisting of a transparent steatite envelope (magnesium silicate). The fuse is packed with quartz powder that serves as an arc extinguishing agent (and, in the case of a liquid-filled HRC fuse, a non-conducting liquid like mineral oil).
2)Expulsion Fuses
These fuses are packed with chemicals such as boric acid, which creates heating gases. The arc is extinguished by these gases and ejected from the ends of the fuse. Copper, tin, or silver are made of fuse material.

 

  • Low Voltage Fuses

The low voltage fuses are divided into five types and those are rewirable, cartridge, drop out, striker, and switch fuses.

1) Rewireable Fuses
They are a quick fuse used in homes and offices that is reusable. A carrier and a socket are composed of them. The carrier is taken out, rewired and placed back in the socket when the fuse is blown, to restore normal service. They are slightly less effective than fuses from HRC.


2) Cartridge Fuses
They are very similar to DC fuses for cartridges. A transparent envelope covering the part of the fuse consists of them. It is possible to plug them in (blade type) or screw them into a fixture (bolt type).


3) Drop Out Fuses
They contain a spring-loaded lever arm that retracts when a fault occurs and must be rewired to restore normal service and put back in place. They are a form of fuse for expulsion.


4) Striker Fuses
 A spring-loaded striker is provided with these fuses that can serve as a visual indication that the fuse has exploded and other switchgear is also triggered.


5) Switch Fuses
High current fuses can be attached or disconnected by a handle that is manually controlled.

electrical fuses display

Ⅲ Conclusion

In the field of electronics or electrical, the fuse is a small safety part in an electrical device or piece of machinery. It is considered the most crucial device which is employed in various electrical circuits. Many types of fuses with stock availability in the business can meet various circuit requirements.

 

Frequently Asked Questions about Fuse Types Basics and Its Applications

1.How do I choose a fuse for my circuit?
In order to select the right amperage of the fuse, you first need to know the full-load steady-state current of the circuit at an ambient temperature of 25ºC (68ºF). Once the current value is determined, then a fuse rating should be selected to be 135% of this value (taken to the next standard value).


2.What is a Type C fuse?
Class C fuses are not dimensionally or electrically interchangeable with other North American fuses. They feature ceramic bodies and bolt-in mounting. They are for short-circuit protection only, in motor controllers, for example, where overload protection is provided by an overload relay.


3.What is a Type D fuse?
D type fuses. D-type (Diazed) fuse cartridges have a bottle-shaped ceramic body with metal end caps and are fitted in screw-in fuse holders. They are available in five different body sizes, with ratings from 2 A up to 200 A (see table). The designation of a size consists of the letter D and a Roman numeral.


4.What are the two characteristics of fuse wire?
Characteristic properties of a fuse wire: (1) It is made up of an alloy of lead and tin. (2) It has high resistivity and a low melting point.


5.What is the difference between Fuse and MCB (miniature circuit breaker)?
Fuse is an electrical device that self-destructs and stops the current flow in a circuit whenever the current exceeds the predefined value. MCBs are resettable circuit protection devices that, on the occurrence of faults, stops the current flow in a circuit.

Ordering & Quality

Photo Mfr. Part # Company Description Package PDF Qty Pricing
(USD)
PTGL4SAS560K6B51B0 PTGL4SAS560K6B51B0 Company:Murata Electronics Remark:PTC RESET FUSE 140V 94MA RADIAL Package:Radial, Disc
DataSheet
In Stock:On Order
Inquiry
Price:
500+: $0.47028
Inquiry
PTGL09AS2R2K3B51B0 PTGL09AS2R2K3B51B0 Company:Murata Electronics Remark:PTC RESET FUSE 51V 522MA RADIAL Package:Radial, Disc
DataSheet
In Stock:549
Inquiry
Price:
1+: $1.25000
5+: $1.20200
10+: $0.97600
25+: $0.84120
50+: $0.72840
100+: $0.66090
500+: $0.55574
1000+: $0.49566
5000+: $0.45060
Inquiry
PTGL12AS0R8K2B51B0 PTGL12AS0R8K2B51B0 Company:Murata Electronics Remark:PTC RESET FUSE 30V 867MA RADIAL Package:Radial, Disc
DataSheet
In Stock:134
Inquiry
Price:
1+: $1.90000
5+: $1.83400
10+: $1.49100
25+: $1.28440
50+: $1.11240
100+: $1.00910
500+: $0.84860
1000+: $0.75686
5000+: $0.68805
Inquiry
PRG18BC4R7MM1RB PRG18BC4R7MM1RB Company:Murata Electronics Remark:PTC RESET FUSE 20V 155MA 0603 Package:0603 (1608 Metric)
DataSheet
In Stock:On Order
Inquiry
Price:
4000+: $0.22489
8000+: $0.19468
12000+: $0.19266
20000+: $0.18998
28000+: $0.18461
1+: $0.60000
5+: $0.57000
10+: $0.49700
25+: $0.43640
50+: $0.36260
100+: $0.30880
500+: $0.26852
1000+: $0.23496
Inquiry
PTGL09AR220M6C61B0 PTGL09AR220M6C61B0 Company:Murata Electronics Remark:PTC RESET FUSE 140V 180MA RADIAL Package:Radial, Disc
DataSheet
In Stock:On Order
Inquiry
Price:
300+: $0.41160
Inquiry
PTGL07AS5R6K4B51A0 PTGL07AS5R6K4B51A0 Company:Murata Electronics Remark:PTC RESET FUSE 60V 290MA RADIAL Package:Radial, Disc
DataSheet
In Stock:On Order
Inquiry
Price:
1500+: $0.38867
Inquiry
PTGL7SAS5R6K4N51A0 PTGL7SAS5R6K4N51A0 Company:Murata Electronics Remark:PTC RESET FUSE 60V 236MA RADIAL Package:Radial, Disc
DataSheet
In Stock:On Order
Inquiry
Price:
1500+: $0.45689
Inquiry
MF-USMF020-2 MF-USMF020-2 Company:Bourns Inc. Remark:PTC RESET FUSE 30V 200MA 1210 Package:1210 (3225 Metric), Concave
DataSheet
In Stock:33000
Inquiry
Price:
3000+: $0.13750
6000+: $0.13500
15000+: $0.13000
Inquiry

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