Circuit Protection Devices: What Are They and What Types Should I Use?


 "If I told you half the things I've heard about this Jabba the Hutt, you'd probably short circuit." Since you’re here, these words said to R2D2 in the film Return of the Jedi are probably not the first time you’ve heard of a short circuit. A short circuit is one of the many issues electronic and electrical protection devices are designed to prevent. 

Let’s talk basics. A protection device simply has two main functions: consistency in regulation, and protection of electrical and electronic circuits. At their most basic, protection devices redirect a power supply into a separate circuit, using overcurrent protection. This allows the device to prevent damage to an existing circuit from excessive voltages and currents. Protection devices also may serve as a safeguard to remove the risk of fire hazard and electrocution. Now that we’re caught up on what exactly a protection device is, let’s cover the most common designs that you might come across and when you might encounter them.

1. Circuit Breaker

  • What is it?
    • Electrical switch
    • Stops a current when there is excess voltage, or when a system failure occurs
  • When is it used?
  • Utilized to protect against an electrical short circuit
    • Useful on both high current and low current circuits 

2.Fuse

  • What is it?
    • Electronic device
    • Metal strip that has the capability to liquify when current flow is too high
    • Categorized by intended application, response time, and breaking
    • When is it used?
    • In systems where protection is needed without a large disruption

3.  Poly Switch (Multifuse/Polyfuse)

  • What is it?
    • Passive electrical device
    • Protects from over current errors
    • Operates as a resettable fuse
  • When is it used?
    • Commonly used on mechanical transforms, computer power supplies, and nuclear or aerospace applications

4.   Residual Current Circuit Breaker (RCCB/RCD)

  • What is it?
    • Electronic device
    • Testable & resettable
    • Shut-off capability - will identify an issue in power supply, and shut off within a short period
    • Does not protect against overload of a circuit
  • When is it used?
    • Home power supply

5.   Surge Protection Device

  • What is it?
    • Electrical device
    • Most common protection unit for over-voltage protection
    • Well organized mechanism
    • Can be used in most stages of a system
  • When is it used?
    • Electrical fitting security systems

6. Metal Oxide Variable Resistor/Voltage Dependent Resistor (VDR)

  • What is it?
    • Electronic device
    • Resistance varies based on incoming voltage
  • When is it used?
    • Applicable with electrical circuits that are vulnerable to electrostatic discharge and/or lighting

7. Gas Discharge Tube/Expulsion Lamps

  • What is it?
    • Electrical device
    • Gas filled tube - electrodes are contained within the gas, and held in an insulated, temperature resistant capsule
    • Able to ionize gas using incoming voltage

  • When is it used?
    • Switching device for electrical protection
    • Lightning protection

8. Inrush Current Limiter

  • What is it?
    • Electrical device
    • Stops inrush current before it reaches circuit breakers and fuses to reduce potential damage
    • High resistance capability
    • Heat protection allows flow of current on a regular basis
    • When is it used?
    • Fixed resistors
    • NTC Thermistors

At Aerospace Orbit, owned and operated by ASAP Semiconductor, we can help you find all the circuits and fuse parts and assemblies you need, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we’re always available and ready to help you find all the parts and equipment you need, 24/7x365. For a quick and competitive quote, email us at sales@aerospaceorbit.com or call us at +1-509-449-7700.


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