It’s easy to find an industrial fuse. Finding the right fuse can be a bit nerve-wracking.
With so many options out there, it’s no surprise that two fuses can look almost identical. The problem? Even a small difference in how they work could lead to serious issues. Guess wrong, and you’re putting both people and equipment at risk.
Most industrial and electrical engineers pick fuses based on how they’re built or used. While it might be tempting to go for the cheapest option, remember – a fuse is a safety device. You can’t afford to cut corners.
Cost aside, how do you specify the right industrial fuse type for your application?
The definition: This is the maximum voltage the fuse can safely interrupt in an overcurrent situation. Every fuse has a voltage rating marked on its exterior.
The challenge: There’s nothing wrong with a fuse’s voltage rating being 2x higher than the circuit’s voltage. There’s a big problem if it’s the other way around. If you apply a fuse beyond its rating, it can arc or spark when it blows.
The product: Regardless of the overall product’s function, it needs a fuse with a voltage rating equal to or greater than the max circuit voltage. A properly rated fuse will protect nearby workers, along with other components in the assembly.
All fuses are straight voltage rated and there is no need to be concerned about the you’ll find in mechanical overcurrent devices. Most low-voltage power distribution fuses have 250 V or 600 V ratings (other ratings are 125 V, 300 V, and 480 V). That said, a 300V rated fuse can still protect a single-phase, line-to-neutral load if supplied from a three-phase, solidly grounded, 480/277 V circuit. In this application, the 300V fuse could only be tasked with protecting the 277 V side of things.
The definition: This refers to the maximum current the fuse can carry without blowing in normal conditions.
The challenge: Your choice of electrical fuse must account for the circuit’s normal operating current.
The product: Buy a fuse whose current rating is slightly above the circuit's normal current, but below the wire’s or device’s current capacity.
The definition: Also known as the interrupting rating, this is the maximum fault current the fuse can safely interrupt flow. It's a measure of the fuse's ability to withstand short-circuit conditions.
The challenge: Improper speccing of interrupt capacity can damage the assembly and create a hazard. The capacity must be higher than the maximum expected short-circuit current in the circuit.
The product: There are dedicated high-breaking capacity fuses, so they’re an obvious place to start. These can safely interrupt currents much higher than their rated current, making them suitable for high-voltage applications.
As a general rule, ceramic fuses come with a higher breaking capacity than glass fuses.
The definition: “Current limiting” is the concept of constraining how much current is deliverable to a load.
The challenge: Any circuit generating or transmitting current needs protection from the harmful effects of short-circuiting and overloading. Insufficient current-limiting ability can result in fire or gas-expulsion hazards in populated areas.
For example, utilities companies often install expulsion fuses or breakers on distribution transformers. This low-current protection is valuable, but isn’t enough on its own.
The product: Some fuses include a feature that allows them to not only interrupt the circuit, but also limit the flow of fault current. A current-limiting fuse throws a proverbial blanket over the impact of a short-circuit, reducing equipment damage and keeping people safe. These specialized components are particularly skilled at minimizing arc flashing at 600 amps and below.
In the case of utilities, by teaming a backup current-limiting fuse with low-current protection, you can also improve power quality by reducing “blink” during faults.
(As a bonus, current-limiting fuses are noiseless, so nearby people won’t jump out of their boots when it’s triggered.)
The definition: Outside factors like climate, particles, and fluids may be present in the fuse’s working environment.
The challenge: There are many environmental threats to electrical devices, and many ways they can wreak havoc:
|
Environment |
Risk |
Which Fuse? |
|
Temperature |
High temps can cause fuse to blow prematurely; low temps can make them less sensitive. Fuses working outside intended range will need derating or uprating to ensure functionality |
Fuses with ambient temperature rating appropriate for any extremes in your application |
|
Humidity |
Moisture can corrode the fuse and hamper its insulating properties |
Fuses with moisture-resistant coatings or hermetically sealed designs to prevent ingress |
|
Flame |
A fire starting is bad; a fire spreading is worse! |
Intrinsically safe fuses with flame-retardant properties |
|
Chemicals |
Chemicals, oils, & gases can be corrosive to – or totally incompatible with – the fuse’s material |
Fuses with materials and coatings resistant to the present corrosives |
|
Vibration |
Fuses, especially high-speed ones, can lose integrity near motors, heavy machinery, & other industrial equipment |
Fuses with a solid build and certified ability to resist vibration |
|
Dust & Particulates |
Combustible dust can cause the current to bypass the fuse. Particle accumulation can cause heat buildup, contamination, corrosion, & arcing |
Fuses with appropriate IP (Ingress Protection) rating for sealing off dirt, etc. |
|
Altitude |
Thinner air can reduce dielectric strength |
Fuses with higher voltage ratings |
The product: As you can see above, some of these challenges come with specific product solutions.
Always consult the manufacturer's datasheets for information on environmental tolerances. When in doubt, discuss your needs with a technical rep who can recommend products that have been tested and proven for similar environments.
The definition: Most types of fuses come in several different dimensions. Generally speaking, the bigger the fuse, the higher its voltage rating.
The challenge: Sizing an industrial fuse must take both electrical and physical needs into account. The fuse’s voltage rating must comfortably exceed your application’s current level, or else it’ll blow needlessly. However, it must also fit inside the assembly without crowding other components, which could lead to heat buildup and other performance issues.
The product: You can start by calculating the maximum and minimum fuse ratings:
Don’t use a “10% rule.” Size the fuse based on safety first, and keep the value well above that of the expected load. Balance this against the internal dimensions of the fuse’s intended home. Spec a fuse to the proper maximum load – one actually possible in real life – to avoid oversizing and overspending on installation.
The Definition: Fuse speed (aka time current) refers to the time between an overcurrent starting and the fuse opening. Most fuses by nature act quickly, but sometimes that’s intentionally not the case. The fuse’s material plays a role in its speed.
The challenge: There are dueling questions you’ll have to confront.
The device needs to balance being fast enough to protect the circuit, but not so excitable that it trips under normal conditions.
The Solution: Choose fuses based on how quickly you need circuit interruption in the event of an overload. In terms of speed, there are four main tiers of fuses:
|
Fuse Speed |
Performance |
Uses |
|
Ultra-Rapid |
Operates at higher temps, often restricting use of low-melting-point alloys. Limited ability to protect against low overcurrent |
Sensitive circuitry, transistors, diodes, etc. |
|
Fast-Acting |
Most common form of general-purpose protection |
Cabling, sturdier components |
|
Time-Delay (Slow-Blow) |
Built-in delay allows brief, harmless currents to pass. Opens in event of sustained overload or short-circuit |
Motor start-ups, inductive load circuits, & other devices with short surges |
|
Dual-Element |
Combo of fast-acting functionality for short circuits and time-delayed responses for overload protection |
Circuits prone to temporary overloads and surges |
The Definition: This fuse accessory absorbs incoming current and helps it flow through the safety device as efficiently as possible. Industrial fuse holders come in a variety of designs, each specific to a type of fuse. Some are removable.
The Challenge: Many common electronic fuses are unusable in conductive paths because of their size or shape. If you want to work with such a fuse, you’ll need a holder to integrate the fuse safely and effectively.
A fuse holder’s design directly correlates to the current rating of the fuse. For example, a cartridge-based holder won’t accept a blade fuse. As a safety feature, many fuses and holders are designed so they literally won’t connect if their current ratings are incompatible.
The Product: Source a fuse holder whose voltage and current ratings are higher than the actual fuse’s. For example, you can use a 30-amp holder on a 20-amp fuse, but you can’t use a 20-amp holder on a 30-amp fuse.
Types of industrial fuse holders include:
|
Holder Type |
Features |
|
PCB Clip |
Lowest cost, but fewest features. Wide application base, but needs insulated from the environment |
|
PCB Holder |
Fixed footprint that offers isolation from contact. Easy to replace (with proper layout) |
|
Panel Mount Holder |
Mounted through enclosure or on backplane. Generally is wire-in, wire-out/line and load. Shields humans from electrical hazards |
|
In-Line |
Wire-in, wire-out/line & load setup creates self-contained harness with wide range of uses. Can make fuse either easy or difficult to access. |
A fuse’s product documentation usually IDs a recommended holder, so look there if you’re still on the fence.
Industrial Fuse FAQWhat factors should you consider when integrating fuses into existing electrical systems?
Additionally, assess the physical space available for the fuse and its holder to provide adequate clearance and protection from external elements. Review the existing system’s documentation and consult with a qualified electrician or engineer to identify potential issues. How often should you inspect or replace fuses in industrial applications? Inspect fuses regularly to confirm they remain in good working condition, especially in environments prone to temperature fluctuations, humidity, or vibration. The specific frequency will depend on the application, environmental conditions, and the importance of the equipment. Generally, conduct annual inspections in industrial settings, but increase the frequency in high-demand environments. You already know to replace a fuse after it trips, but consider replacing it at other times based on its condition, age, and compatibility with any system updates. Follow the manufacturer’s guidelines to determine replacement intervals and conduct preventive maintenance. How do you properly test or verify that a selected fuse will perform as expected in its intended environment? To properly test a fuse, subject it to conditions that simulate its intended operational environment, including voltage, current, temperature, and other relevant factors. Conduct electrical testing to verify that the fuse reacts appropriately to overcurrent situations by interrupting the circuit at the specified ratings. Consult the fuse’s datasheet and confirm compatibility with your equipment before installation. Manufacturers may also provide testing services or guidance to confirm that the fuse performs as expected in real-world conditions. Perform field testing under controlled conditions as another method to confirm performance before deployment. |
An industrial fuse is a safety device with huge implications. Not exactly time for a guessing game, or a decision based solely on price.
Voltage rating and amperage tell you about the normal operating conditions a fuse can handle. Interrupt capacity and current-limiting ability are indicators of how the fuse behaves under fault conditions.
Beyond pure electrical properties, there are several other factors that can have a say in your project’s success. Make sure your industrial fuse manufacturer can meet the criteria most important to your equipment.
If you’re ready to explore sourcing options, click below for a manufacturer list:
This article was originally published in Nov. 2023 and was recently updated to reflect current industry trends.