AROUND THE CIRCUIT

Standby Versus Prime Power Generator

In Guyana, self-generation of electricity is fairly common. Some people use generators as backup to the utility supply, operating the generators only when there is an outage on the utility grid. Others use generators as the main source of power, either because there is no utility service available, or because they believe it is cheaper to operate a generator than to buy electricity from the utility. For either of these two basic applications (standby or main power source), the question should be asked: are the generators being used most suited for their particular application?

Power generators have one of three classifications: standby, prime or continuous. Standby generators are typically built to work for short durations, operating just a few hours at a time to provide backup power when there is a failure in the utility supply or the primary power source. As such, they are not as robust as the prime or continuous power generators. Since they are expected to work for a limited time on any occasion, standby generators are equipped with smaller cooling systems than generators of the other classifications, and their alternators are not designed to withstand high temperatures for a prolonged period.

In contrast, the prime and continuous power generators are built to operate as the primary energy source, to work continuously or for extended periods. They are, generally, more robust and rugged, equipped with large and sometimes elaborate cooling systems. Their alternators carry heavy-duty windings and insulation, with the cooling system limiting the temperature rise of the alternator during operations.

The main difference between the prime and continuous power generators is that prime power generators are designed to run for long periods at variable loads, while continuous power generators are designed to run continually with a somewhat constant load. Continuous power generators do not work well with variable loads, and are not designed to handle overload conditions. Conversely, prime power generators are generally designed to handle about 10% or so overload for short durations.

Both prime and continuous power generators are usually more expensive than standby generators of similar capacities.

Before you purchase a generator, it is important to consider the purpose for which the generator will be used. Operating a standby generator for periods longer than prescribed is likely to lead to malfunctioning and frequent failures, resulting in higher maintenance cost. The useful life of the generator could also be shortened. A standby generator is ideal for use as a backup to a reliable primary power source. In such a case, it will only be used for short durations during power outages. If you are in an environment where outages from the primary source are frequent and prolonged, then you should consider investing in a prime power generator instead of a standby.