Paul Newton
With the ever-growing popularity of multifunction fire apparatus-trucks that can do anything and everything-having adequate onboard power is critical.
In addition to lighting the scene, line voltage (AC electricity) on an apparatus can be used for powering communications, extrication, and ventilation equipment and anything else that requires a 110- or 220-VAC source. Many departments choose to specify cord reels with line voltage outlets as well as outlets in the cab and around the body. Although each location will have an individual current rating, the total amount of power you will be able to draw will depend on the power source's capacity. Proper power source specification is critical to ensuring that your apparatus will live up to your expectations. Fire Apparatus Manufacturers' Association (FAMA) member companies can provide a variety of solutions.
Power Sources
An inverter or generator produces AC electricity on an apparatus. Inverters are small-capacity units that convert 12-VDC battery power to 110-VAC power. These units may be adequate for communications equipment or other low-current applications. But for most serious uses, you will need a generator.
Power Needs
Before considering the type of generator you want, you must first determine the amount of power you will need. Take inventory of all the AC devices you will have on the apparatus or that you will be powering from the apparatus, and list the power requirement for each in kW. Think about which devices you will be running at the same time, and come up with the configuration that will require the greatest total power. Add a safety factor of 15 percent or some other value you feel comfortable with, and use this value to size your generator.
Generator Types
When we refer to generators, we are referring to the entire system of parts that make up the power-producing unit. The system may consist of many parts such as motors, belts, shafts, engines, and reservoirs. However, all generators include an alternator. When the alternator spins, it produces power. How we spin that alternator is where the difference in generators appears. There are four main generator types, each with its own pros and cons.
Gasoline
Gas generators typically come in sizes from three to 10 kW. They are the least expensive but also the least capable of the generator options. Since nearly all modern apparatus are diesel-powered, your gas generator will require its own source of fuel. Power will be available anytime the generator is running, whether the apparatus is mobile or stationary. Apparatus design will need to include an additional exhaust system as well as a means of keeping the generator cool during operation. Gas generators can be a good choice for low-power, intermittent use and when the budget is tight.
Diesel
Diesel generators have most of the same installation considerations as gasoline generators-a good location for an exhaust pipe and accommodations to keep the generators cool. Since they run on the same fuel as the apparatus, they do not require an extra fuel tank. Available in sizes from 10 to 50 kW, diesel generators are a good choice for continuous use for high-power applications.
Hydraulic
Hydraulic generators don't need their own power source because they use mechanical power from the main apparatus engine. A power take-off (PTO) on the transmission transfers power, which turns a hydraulic pump. This pump creates pressure in the hydraulic fluid that flows through a hose to drive a hydraulic motor directly attached to the alternator. The alternator and cooling system can be located anywhere on the apparatus and will provide power with the apparatus either stationary or on the move. Hydraulic generators are a great choice for heavy-duty or continuous operation-up to 50 kW-where space is at