vibration, corrosion were once considered the primary causes for the
failure of 12/24Volt electronic equipment. No Longer! High density
silicon chips and other low voltage electronic components are failing because
of external Electrical System
the harsh Marine environment, a recent survey showed that over 50% of electronic
equipment failures were traced to some form of electrical supply problem. Unfortunately
many design engineers still think 12 and 24/28 Volt power systems provide
'pure D.C.' power because "the presence of a battery provides an infinite
sink that absorbs all faults". Nothing could be farther from the
truth. And, therein lies the problem.
and Marine electronics fall prey to definable classes of faults found in
D.C. electrical systems.
Fault classes are:
(Click on Sidebar for more details)
Mobile and Marine power systems are more problem-prone than their AC mains powered counterparts. Have a look at each of the fault links for details on their characteristics and effects.
The first effect of these faults is unreliable operation of the installed equipment. For example, if you look at the section on 'UnderVoltage' you'll discover that even in 24/28 volt power systems, battery voltage will drop to 6 volts during engine cranking. Under MIL-STD-1275B specifications, this is considered normal for properly maintained and operating DC power supplies.
Likewise, Ripple from alternators, AC inverters, or main powered battery chargers can produce noise and hum that interferes with the operation of radio, sonar and audio equipment.
Other faults, can cause memory loss, 'glitches', or lead to premature failures.
Damage to Electronics:
In some instances, a single fault 'event' will cause the immediate failure of a component. More often, the damage is cumulative and thus more insidious and much more difficult to diagnose. Equipment performance is degraded slowly - often going unnoticed by those who use it everyday. Or, the damage may be manifest as unrepeatable problems that are often dismissed as 'glitches' or 'software bugs'.
Intensive post-mortems of failed equipment reveal that components were damaged and degraded by exposure to a long succession of high voltage events. The accumulated effects weaken semiconductors and other components. Eventually failure occurs. Often, these damaged components fail when stressed by other normal environmental factors - like increased temperatures. However, the real cause of the failure is not heat, but rather, the repeated effects of exposure to electrical system faults.
Standard 'Solutions' Lead to Further Problems
Many different devices and techniques have been tried by engineers in the past: MOV's (metal oxide varistors), zener and avalanche diodes, passive filters, capacitors, fuses, circuit breakers etc. Devices used to suppress surges from lightning strikes work well for that purpose, but cannot be used safely to protect low voltage power systems found in the mobile and marine environment. One reason is that these devices are generally rated for very small power levels (watch for devices rated in 'joules'). They tend to burst into flames when exposed to sustained overvoltages! To counter this catastrophic consequence, engineers have to select devices with very high 'clamping voltage' levels, which effectively removes any benefit from their use!
Applying one of the 'standard solutions' might work if all you had to worry about was fast rise time surges caused by lightning strikes. But, proper protection
means that you have to suppress or remove ALL electrical system faults
- not just one! Standard devices are not capable of doing this.
the alternative of leaving equipment unprotected is unacceptable when high
reliability and low maintenance costs are of paramount importance.