What is Prime Power and Continuous Power?
Prime power refers to generators used as the main source of electrical power. Prime power generators are designed to operate for long periods of time at variable load.
A typical prime power generator set may operate an unlimited number of hours per year. Because of this, its power output from both the engine and generator will be less than for a standby generator set. It will allow up to a 10 percent overload from its rating for as much as two hours per day (up to 8 percent of its total operating time). The rest of the time the set will operate under varying load conditions that are less than its rated power output.
The continuous power generator set may run an unlimited number of hours per year. The load is usually constant at 100 percent of the continuous rating for the engine and generator. This is the most conservative rating for both the engine and the AC generator.
Checklist of Things to Consider
Common single phase voltages in North America are 115 & 230. These voltages are often supplied by generator sets as they are frequently used in household type loads.
Common three phase voltages found in North America are 139/240, 120/208, 277/480 and 347/600. (Measured – line-to-neutral/line-to-line)
Most of North America is 60 Hz or 60 cycles per second for AC power supply. It is not uncommon to have European or Asian equipment to power and this is usually 50 Hz. AC supply.
To produce 60 Hz power, engine driven generators will operate at 1800 rpm using a 4-pole generator. Lightweight, portable or residential generators may operate at 3600 rpm with a 2-pole generator. Larger generator sets may run at 1200 rpm (6-pole) or 900 rpm (8-pole) or 720 rpm (10 pole). (50 Hz is similar but 3,000 rpm for 2-pole, 1500 rpm for 4-pole, 1000 rpm for 6-pole etc.)
Residential and most light commercial services are single phase, 115/230V. Larger commercial and industrial services are normally three phase. Although there is no hard and fast rule, generators over about 50 kWe are usually three phase. On larger sets, if the loads are single phase loads, the line-to-neutral power is divided, as equally as possible amongst the phases to balance the loads on the generator’s windings.
In this case, “kilowatts” refers to generator output kilowatts or kWe (sometimes ekW). The actual load on the generator set engine are the kilowatts required to operate the load. This should be carefully sized because the engine cannot be efficient without an adequate load. Too little load may cause diesel engines to “carbon up” with unburned fuel. This leads to sooting of the lubricating oil, component wear and eventually, premature engine failure. Conversely, too much load can shorten the life or damage the engine and generator.
kVA is apparent load on the generator. The generator must be sized for the kVA requirement. Typically we use 0.8 as a power factor to estimate kVA. This is a convention and the power factor should be used if it is known. If the power factor is estimated, then the kVA will be the kWe ÷ 0.8 = kVA. (e.g. 100 kWe = 125 kVA where the power factor is 0.8)
What will be the highest and lowest temperatures at which the generator will be expected to function? What will the maximum altitude be? Will it operate in dusty conditions? This will affect the air cleaner and pre-cleaner selection and may affect the fin spacing on the cooling radiator.
If the generator will be housed in an enclosure you may want to think about the possibility of the enclosure being affected by ice buildup or other weather related concerns. Service access will normally be looked after by the supplier but deserves consideration. Is sound attenuation required?
The end use of the machine will determine what engine best suits the job. As a rule, the larger the displacement, the slower the speed (rpm) the longer the life. However, a large displacement, slow speed engine is not the right engine for a portable application. So thought needs to be given to what the set will do over its intended lifetime. If you want to move it on site and leave it running for many years, you will select a different engine than someone looking for a generator set that can be readily relocated.
Sizing the engine properly is extremely important both for operating efficiency and for longevity. An engine operating with a light load cannot be efficient. In fact, light loads for extended time periods can cause serious damage to the engine.
If the prime power generator is going to be located in close proximity to people or sensitive ecosystems, controlling the noise level of the generator is another factor that needs to be considered. Advance planning for sound attenuation includes having sufficient space for a suitable exhaust system and, if required, for an enclosure.
Find Your Generator
Below are links to our generator manufacturers’ websites and brochures and to our PowerLine and Remote Site Generator products.
Have a look around and then give us a call to discuss your requirements.
If you are looking for a prime power generator, you are a candidate for the PowerLine product.
Frontier’s PowerLine Generators (6.5 to 400 kW)
Our PowerLine generators are built using Kubota, John Deere, and Mitsubishi engines.
Kubota’s Quiet Power Generators (13.5 to 26.5 kW prime)
Kubota’s SQ line of super quiet generators are equipped with an over-sized muffler and in the case of one model, a second muffler!
Kubota’s GL Series Lowboy Generators (6.5 to 10 kW prime)
With compact size and low noise levels, the range of applications is endless.
Our RER (Remote Extended Run) generator set is designed to provide reliable operation in remote locations, and to extend regular service intervals without any sacrifice in performance or overall equipment life.
GE’s Stationary Diesel Generator Sets (1 MW to 3 MW)
Prime or continuous power, black start or standby, GE offers reliable, fuel efficient, medium speed engines.
If durability and operating efficiency are high on your list of requirements, a GE generator set may be right for your application.
Frontier’s Long Run Oil System Package
Our Long Run Oil System™ package is available on most of our prime power generator sets. This package offers extended oil change intervals up to 3,000 hours (125 days) without sacrificing the life of the engine.