We live in a world of mobility and portability. A myriad of facilities, once existing only in stationary environments, operate today in mobile venues called specialty vehicles. They can be broken down by their three major user categories:
The purpose of a general road vehicle is to transport people and/or merchandise. Once it is equipped with any exceptional or out-of-the-ordinary accessories, it becomes to a lesser or greater degree, a specialty vehicle. The demand for specialty vehicles is far less than that for common ones. It is for this reason that many are born of a standard base which is modified in order to customize it for special functions.
In the civilian category ambulances, fire trucks, police surveillance vans, limousines, ice cream trucks and concession vehicles are only a few. Utility power trucks, insecticide sprayers, forklift trucks, loggers, mining vehicles and locomotives are industrial illustrations. Tanks, Humvees and artillery transporters are among military specialty vehicles.
There are two streams of construction that go into the making of a specialty vehicle, the mechanical and the electrical. The mechanical aspects are amply familiar to most because their manifestations are plainly visible. therefore this article will focus solely on the electrical.
DC-DC Converters and Inverters in custom vehicles are installed and act as extensions of the battery-and-alternator based electrical system. Power converters are the key to interfacing the power demands of extraordinary electrical equipment with the specialty vehicle electrical system. A good illustration is an ambulance whose typical installation includes apparatus such as EKG machines, chart recorders, oxygen and communications equipment. North American ambulances have a 12 Volt DC primary electrical system, however the medical equipment within may have various types of power requirements. Much of this expensive equipment is designed for operation with 120 Volt AC since most of its usage is found in the hospital environment. Some ambulance on-board computers may also operate on 120 Volts and specialty display monitors may require 24 Volts. Unlike ambulances inter-city tour buses have 24 Volt based systems. To operate communications equipment available in 12 Volt versions only, 24V to 12V step down converters are used. Many travelers utilize computers and require the facility to recharge and power their laptop with 120 volts AC during prolonged hours. The 24 Volt DC to 120 Volt AC inverter is commonly used to provide the bus-computer interface.
Unlike civilian specialty vehicles, industrial ones are equipped to function in industrial or natural resource extraction environments. Mining trains are equipped with DC-DC converters to power communication radios and computers from the train’s 72 Volt DC system. Industrial painting trucks use PLC’s (programmable logic controllers) which are powered by electronics typically requiring 24 Volts DC. PLC’s are also used on board fertilizing and pest control trucks. Refrigerators and point of sale terminals in food concession trucks may be powered by DC to AC inverters. All of these trucks have electrical systems which are 12 Volt based.
When it comes to preemptive electrical design, military vehicles champion them all. Unlike the above examples, not only are they equipped to power electrical apparatus logically associated with military use, they are rigged to power civilian equipment in extraordinary circumstances. DC-DC converters and trailer electrical interfaces make this possible.
Modern western military powers belong to the NATO alliance (North Atlantic Treaty Organization which derives its name from the geographic location of its original member countries). Today, after 7 occasions of expansion, there are 28 member countries and important associated countries such as Australia and Japan in the military block. Therefore it is no coincidence, that many electrical standards in the world’s military vehicles have been influenced by NATO. Military vehicles must be in ready preparedness to venture anywhere on the globe to deal with war or natural disaster. This requires that they have universal electrical capabilities. A prime example is a military water tanker trailer. When natural disaster strikes, clean drinking water is usually the first necessity. These tankers are designed such that they can be towed not only by a military truck but also by any civilian truck of virtually any country on the globe. The converse may also hold true. During emergencies, military vehicles are expected to have the capability to couple with most civilian vehicles. When taking into account the varying transportation vehicle standards around the globe, it has taken years of innovative electrical power conversion designs to overcome the challenges.