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Type d fuses
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D-type fuses

D-type fuses are an inseparable protection element in every electric circuit control installation of industrial machines with high currents. The trade nomenclature also often uses the name circuit breaker . Due to the time-current characteristics, fuses are classified into four groups A, B, C and D. These devices protect against the effects of overloads and short-circuits in the control lines of industrial installations by interrupting the power supply to the circuit . D-type fuses reduce the consequences of failure and exclude electric shock to the personnel. They also limit the possibility of an explosion or fire.

D-type fuses - structure and parameters

Standardization of sizes and methods of fastening of all control and control elements of industrial automation systems also included devices from the security sector. Their modular structure, most often in configuration as a three-pole fuse , but also single or double-pole variants are available. An example is the 3-pole D 40A circuit breaker manufactured by EATON. The standard width of one module is 17.7 mm, which enables any configuration at the workplace. On the front panel there is an on / off lever and indicators informing about the current operating mode.

The standard modular design of the circuit breaker gives the possibility of connecting it from above . Such a cable routing system in their fuses is used, among others, by Legrand, SCHNEIDER ELECTRIC, and Hager. Busbar at the bottom is also available in all of the above solutions. This facilitates the process of possible replacement and control of the system operation. The design of most types of miniature circuit breakers allows them to be mounted on a standard TH35 DIN rail. The range of resistance to external temperature is -25 degrees to +70 degrees Celsius.

The time-current parameters of fuses determine their suitability for particular tasks:

  1. Type A - rare, used in security of electronic devices. Characterized by immediate action.
  2. Type B - the most numerous group of fuses, designed for building and residential installations. They protect lighting lines and socket circuits.
  3. Type C - used for the protection of industrial lines. They are characterized by an increased value of inrush currents.
  4. Type D - type D fuses are used in heavy industry to protect devices with high inrush currents. They are installed as protection for turbines and power generators.

Miniature circuit breakers - characteristics

The type D automatic fuse is used locally and allows protection against the effects of overloads of working machines. As a rule, it protects individual high-power machines. It is mounted directly on the enclosure of the protected device or in its vicinity as a separate element.

The technical specificity of D-type circuit-breakers indicates that they do not cause premature power outages and respond adequately to electric overload . The operating time range of the bimetallic release is between 1.13 and 1.45 times the rated current. On the other hand, the trigger threshold for an electromagnetic release is 10 to 20 times the circuit breaker rated current. These values ​​are appropriate for the characteristics of the individual groups of switches. The maximum rated currents for specific fuses are as follows: 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A. After these values ​​are exceeded, the power supply to the circuit is interrupted of the working machine