Category | Fuses

Parallel and Series Connection of Fuses

Posted on 21 April 2020

              Fuses connected in parallel In North America, the Electric Codes do not permit the paralleling of overcurrent protection devices in the field, although paralleling is permissible in a factory built assembly. Current rating: When two fuses are connected in parallel it is necessary to ensure that they share [...]

Semiconductor Fuses - General

Posted on 20 April 2020

  Figure 1. Possible arrangements for semiconductor fuses in a converter bridge (a1 and b1) and for an AC controller (a2 und b2); a) Arm fuse or b) Phase fuse Diodes and thyristors do not limit short-circuit current. For this reason, external measures have to be taken to ensure short-circuit protection. The silicon chip of [...]

Semiconductor Fuses: Terms and Explanations

Posted on 18 April 2020

  Below is a guide to terms commonly used to characterize semiconductor fuses. Rated voltage VN Maximum permissible voltage with maximum 10% permissible short-time increase. If the rated voltage is an AC voltage, this will be specified as an effective value. This applies to a sinusoidal voltage of 50 - 60 Hz. For non-sinusoidal voltage, [...]

Time-Current Characteristic for Fuses

Posted on 15 April 2020

              If a fuse is subjected to a current greater than the minimum current required to produce melting, the fuse element will melt. The higher the current, the shorter the melting time will be. This inverse relationship is shown graphically by the time-current characteristic (TCC). Figure 1 shows a typical time-current [...]

Dimensioning Semiconductor Fuses

Posted on 15 April 2020

  The following fuse-related data must be considered when dimensioning semiconductor fuses: Rated current Rated voltage Operating i²t value Switching voltage Dimensioning semiconductor fuses on the basis of the rated current At rated current, a fuse link can be continually loaded under certain circumstances, i.e. at 20°C ambient temperature in unobstructed air. The current has to be [...]

I²t Curves and Operating Times for Fuses

Posted on 08 March 2020

  Melting I²t For high short-circuit currents, which cause melting in times of the same order as the AC cycle, the melting time varies greatly, depending upon whether the short-circuit current waveshape is symmetrical or asymmetrical. In these cases the time-current characteristic is of limited value, and the coordination of system protection is done using [...]

Introduction to Current Rating for Fuses

Posted on 02 March 2020

              The rated current In of a fuse is a value assigned by the manufacturer, and is the r.m.s. (root mean square) current which the fuse is designed to carry continuously under specified test conditions. In this respect, it is no different from the rated current of any other [...]