Circuit Protection

Traditionally, circuit protection revolved around the decision of whether to use glass fuses or circuit breakers. Standard decision criteria include voltage of the circuit, amperage of the circuit, frequency of the power source, operating conditions and available fault current. Users should also determine the types of failures that might occur and match the overload characteristic to the performance capability of the breaker. Functional requirements such as visual inspection, switching or auxiliary circuits must also be defined.

Phoenix Contact offers a complete line of fuse holders and circuit breakers to meet the most demanding operational conditions in circuit protection.

Fuse Holders

Fuse holders from Phoenix Contact are manufactured in the following designs: DT, QT, ST, UK and UT versions. Designed to protect your system in various packages, whether you prefer spring cage, screw clamp or insulation displacement technology, you will find high quality fuse holders for your DIN rail application.

TCP

Thermal circuit breakers are ideally suited for AC and DC applications, such as to protect motors, transformers and actuators against overloads. Miniature thermal breakers offer overload protection and low interrupting capacity in a compact pluggable package. Mini thermal breakers are not usually used as a replacement for a circuit breaker, but as a glass fuse replacement. Interrupting capacity is the maximum fault current that can be repeatedly interrupted without failure of the breaker.

TMC

Thermomagnetic circuit breakers combine the advantages of thermal and magnetic trigger mechanisms and are typically used in information and communication technology as well as process control.

ECP

Electronic circuit breakers are designed specifically for elective protection of all load circuits that are fed by 24V DC power supply unit. They respond to overload or short-circuit faster than the power supply unit, and they selectively disconnect the faulty load circuit before the power supply disconnects all connected loads to protect itself.

All fuse holders and circuit breakers from Phoenix Contact are manufactured with touch-proof insulating housings which can be labeled with various marking solutions.

How to Choose a Circuit Breaker

• What is the normal current load (nominal current)?
  Specify the size of the breaker in amps based on the normal current load.
    
• What types of failure might occur?
  Match the short-circuit and overload characteristics to the performance capability of the breaker.
   
• What is the rupture capacity?
  Specify the breaker knowing the maximum fault current that can be repeatedly (3x minimum) interrupted without failure of the breaker.
     
• What is the maximum interrupting capacity?
  Choose the breaker knowing the maximum current at a given voltage that the breaker can interrupt safely without damage to surrounding components.
     
• How fast must the circuit breaker react to a fault condition?
  Specify a breaker by selecting a speed that avoids nuisance tripping but protects against component damage.
     
• How many poles are needed?
  Determine the number of poles connected electrically and structurally that are needed.
     
• What are the functional requirements of the breaker?
  Define the requirements for visual inspection, switching, auxiliary circuits, or space.
     
• What size wire must the breaker accommodate?
  Determine if the breaker can accept the wire sizes required.
     
• What are the environmental factors: temperature, moisture, vibration?
  Determine if there are unusual conditions in which the breaker must operate.

Further information and services related to this article