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Semiconductor Fuse Types and Classes


What is a Semiconductor Fuse?

Also known as ultra-rapid fuses, high speed fuses or rectifier fuses; a Semiconductor fuse is a high speed current limiting fuse that is designed to protect and isolate sensitive semiconductor components such as diodes, thyristors, SCRs etc. by minimizing the I²t, peak current let-through and arc voltage.

Semidonductor fuses generally range from 125 to 2,100 volts and are available in a wide variety of shapes and sizes.


Semiconductor Fuse Classes

Semiconductor Fuses fall into three classes which characterise the breaking (interrupting) characteristic of the fuse - aR, gR and gS.These fuse speed markings are often printed on the fuse to help you identify it. Typical applications for semiconductor fuses include protection of semiconductors (diodes, thyristors, triacs, etc) used in power rectifiers, UPS, converters, motor drives (AC and DC), soft starters, solid state relays, photovoltaic inverters, welding inverters and any application where it is necessary to protect semiconductor devices.

• aR Class Fuses

aR class fuses only provide partial-range breaking capacity (short-circuit protection only) for the protection of power semiconductors (IEC Utilization category). Note: aR fuses are often faster (with a lower I²t value) than a comparable gS or gR fuse. An aR class fuse must not be used as a replacement for a gR class fuse.

• gR Class Fuses

gR class fuses provide full-range breaking capacity (overload and short-circuit protection) for the protection of semiconductors, cables and all switchgear of the installation. Designers can often substitute a gR class fuse for an aR class fuse.

• gS Class Fuses

gS class fuses are very similar to gR class fuses. They both provide full-range breaking capacity (overload and short-circuit protection) but gS class fuses have lower power dissipation than gR class fuses due to tighter melting gate values. This also results in gS class fuses having lower fuse body temperatures.

Differences between aR Class and gR / gS Class Fuses

aR class fuses feature a high minimum interrupting current as compared with their current rating. The primary timecurrent characteristic of aR class fuses is the CC'curve, above which another protection device must be associated.

The gR class fuse represents considerably improved performance in semiconductor protection.gR class fuses should be used in the design of low voltage equipment and in the protection of power electronics equipment.

Start protecting your new equipment with gS class fuses and gR class fuses today. These fuses offer enhanced protection, safety and reliability, along with reduced risk of replacement errors and assembly costs.

Diagram of semiconductor fuse aR vs gR curve

Difference between a fast acting fuse and a semiconductor fuse?

A fast acting fuse protects equipment and wiring by reacting to short circuits quickly, but the reaction time is not quick enough to protect sensitive semicondutor components. Installing a fast acting fuse in place of a semiconductor fuse can result in damage to your equipment and is never recommended. When replacing a semiconductor fuse with a fuse that is not exactly the same as the original fuse, you need to ensure that i2t value of the new fuse is not greater than the i2t value of the original fuse. These values are usually specified on the manufacturer datasheet. Please contact our staff if you require help choosing a replacement fuse. Customer Feedback


Semiconductor Fuse Types

The type of semiconductor fuse you need will depend on the manufacturer's specifications. It is important to check the voltage range required of the fuse needed, i2t value, and the casing style (which is typically listed as bolt-in, blade, ferrule or hockey puck). Some of the most common types of Semiconductor fuses are;

• DC Power Semiconductor Fuses

These fuses are designed for use in Direct Current (DC) voltage circuits. DC semiconductor fuses are designed to create a larger gap and melt quicker than Semiconductor Fuses specifically designed for use in AC voltages. This is necessary as the voltage in a DC circuits does not pass through a zero point. The majority of semiconductor fuses we sell are designated for use in either DC or AC circuits. The fuse will usually be marked with the voltage ratings the fuse can operate within. This voltage rating is the maximum rating, the fuse will work fine in lower voltages, but the voltage should not exceed the specified maximum voltage rating of the fuse.

Swe-Check Semiconductor Fuse Range
View our range of DC Power Semiconductor Fuses


• Battery Protection Semiconductor Fuses

These are a relatively new special range of ultra rapid fuses that are specifically designed to prevent overheating of battery cells in battery storage and UPS systems. They may be classed as semiconductor fuses due to their quick reaction time, but they do not protect semiconductor devices. *list relevant products here*

Battery Protection Semiconductor Fuses
View our range of Battery Protection Semiconductor Fuses


Still not sure what Semiconductor Fuse you Need?

Contact one of our fuse experts today on +61 3 9521 6133 or use our fuse finder page if you know the Fuse Speed, Voltage Type, Voltage Rating and/or Ampere Rating.


Customer Feedback

" Customer service is fantastic. Thankyou Richard. Overnight delivery is a definite plus as well as a great selection of products. Hope to use again. Keep up the good work. "

Derek D
Received 8/10/20

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