The importance of fuses in radio equipment power supplies
A safe two-way radio equipment installation requires the ability to quickly disconnect the supply to the equipment, if a fault develops. Fuses are a cost effective solution, for equipment safety.
What are Electrical Fuses
Fuses are devices that protect equipment installations, from excess electrical current.
Excess current is caused by a fault in the equipment, or system wiring, and can cause equipment damage, or even fire.
The fuse works by ‘blowing’ if a certain current through it is exceeded. When the fuse ‘blows’, the electrical current ceases to flow, due to a physical break inside the fuse, preventing current flow through it.
Types of Fuses
Electrical fuses come in a variety of package types, and current ratings.
For example, package types include ‘cartridge’ and ‘blade’ designs.
Fuses are also made to blow at different current thresholds, so can be matched to the piece of equipment it is connected to.
There are also fuse types known as ‘slow blow’ fuses.
Slow Blow fuses are designed not to blow due to a short spike in electrical current. Short spikes can be caused by surge currents, which is a very temporary increase in current, when a piece of equipment is started.
Importance of correct Fuses
Fitting an incorrect fuse can either reduce safety, or reliability.
For example, if a fuse is fitted that has too high a current blow rating, then if a fault develops with the equipment, the electricity will find another weak point in the system. This weak point could be the radio equipment itself, and the excess current could damage it.
On the other hand, fitting a fuse that has too small a current rating will reduce system reliability.
This is because the current being drawn by the radio equipment is more than the fuse can cope with, and therefore will blow.
Two way radio equipment, draws less current when receiving, than when it is transmitting. Therefore the fitting of a too small fuse, may not become apparent, until the two way radio transmits.
Always refer to the manufacturers equipment specifications to understand the maximum current that the equipment will draw, and select a fuse slightly larger.
If no manufacturers data is available, then using an Ammeter in series with the DC supply, can determine the current drawn. Remember however, to also test on transmit, and with maximum transmit power selected (if an option).
(c) 2018 Craig Miles / Yesway Ltd.
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