Category | Fuses

Basic Considerations for Semiconductor Protection with Fuses

Posted on 23 April 2013

              Solid state devices have progressed through several generations of sophistication since their introduction in the 1940s. Fuse designs have changed to match solid state protection demands. The protection task seems simple - choose a fuse of correct voltage and ampere rating which will protect a solid state device [...]

R-rated Fuses for Medium Voltage Motor Protection

Posted on 06 December 2012

              Fuse Application Guidelines The guidelines for applying R-Rated fuses are significantly different from those applying to low voltage motor fuses. This is because R-Rated fuses are back-up fuses which are intended to provide short circuit protection only for medium voltage starters and motors. An R-Rated fuse is not [...]

Let-Thru Current and l²t for Fuses

Posted on 15 November 2012

              Current limitation is one of the important benefits provided by modern fuses. Current limiting fuses are capable of isolating a faulted circuit before the fault current has sufficient time to reach its maximum value. This current-limiting action provides several benefits: It limits thermal and mechanical stresses created by [...]

Basic Fuse Construction and Operation

Posted on 25 October 2012

              The typical fuse consists of an element which is surrounded by a filler and enclosed by the fuse body. The element is welded or soldered to the fuse contacts (blades or ferrules). Figure 1. A typical fuse The element is a calibrated conductor. Its configuration, its mass, and [...]

Preferred Fuse Placement

Capacitor Protection with Semiconductor Fuses

Posted on 24 October 2012

  The primary responsibility of a capacitor fuse is to isolate a shorted capacitor before the capacitor can damage surrounding equipment or personnel. Typical capacitor failure occurs when the dielectric in the capacitor is no longer able to withstand the applied voltage. A low impedance current path results. The excessive heat generated builds pressure and [...]

Low Voltage Fuses For Motor Protection

Posted on 22 October 2012

                      Code Requirements for Motor Protection The NEC or CEC requires that motor branch circuits be protected against overloads and short circuits. Overload protection may be provided by fuses, overload relays, or motor thermal protectors. Short circuit protection may be provided by fuses or circuit [...]

How To Read A Fuse Time-Current Curve

Posted on 16 October 2012

  A time-current characteristic curve, for any specified fuse, is displayed as a continuous line representing the average melting time in seconds for a range of overcurrent conditions. The melting time is considered nominal unless noted otherwise. Several curves are traditionally shown on one sheet to represent a family of fuses. The family shown below [...]

Interruption of DC Fault Currents

Posted on 11 July 2012

              For a fault in a DC circuit, the prospective (available) short circuit current is the final constant value VDC /R, where VDC is the source voltage and R is the resistance of the circuit. After a fault occurs, the current in the circuit increases exponentially, as shown in figure [...]

Introduction to Semiconductor Fuses

Posted on 14 June 2012

              A fuse is a device for protecting an electrical system against the effects of overcurrents (excess currents), by melting one or more fuse elements, thus opening the circuit. Very fast-acting fuses are widely used for the protection of diodes, thyristors, and other power semiconductors in AC and DC [...]

Fuse Placement in Typical Converter Circuits

Posted on 25 April 2012

                The article "Semiconductor Fuses – General" describes some of the fundamental principles that guide the positioning of fuses in power electronic circuits. Below are several examples of how these principles are implemented in typical converter circuits.   Phases Bridge   Phases bridges have many different kinds of [...]