Before Choosing A Generator, There Are A Few Things To Think About
Around the world, generators are the lifeblood of construction sites, infrastructure projects, and outdoor events. Their contribution to productivity cannot be overstated as a versatile, dependable power source: they can provide vital energy and support to applications as diverse as urban de-watering projects, manufacturing industries, hospitals, or powering a mobile kitchen serving 5000 people in a remote location, to name a few.
However, while it is understood that a Diesel Generators is always there and is frequently the unsung hero of the show, there may be some elements that need to be addressed before a purchase or rental decision is made, particularly in terms of comparative performance and unit size.
The enormous inrush currents involved with starting electric motors and transformers, which are often six times the maximum load current, are the most significant factor to consider when sizing a generator. Inrush currents for today’s high-efficiency motors, on the other hand, can be nearly quadruple that amount.
As a result, it’s become standard practice to use the beginning kVA needs of motors and transformers to calculate the size of a generator. This technique frequently leads to generators that are larger for the motor running load rather than based on the application’s real demands. Furthermore, it ignores other important aspects that influence generator sizing. For example, harmonics are produced by variable frequency drives and motors that start sequentially.
If the generator set is not sized appropriately, severe voltage and frequency dips might occur while starting motors or transformers. Other loads connected to the generator output may be more susceptible to voltage and frequency dips than the motor or motor starter, causing issues. Thankfully, assistance is on the way.
Many generators now include options for dealing with the additional excitation systems needed in the alternator. A permanent magnet or auxiliary winding are the two most common alternatives. Both use a residuary excitation current to supply three times the generator’s nominal current to cover inrush peaks from the electrical motor for a minimum of 10 seconds.
There are even more complex choices available in some circumstances. Some generators, for example, include a digital automatic voltage regulator (D-AVR) that is built particularly to withstand the high inrush currents involved with starting motors and transformers. Because the transient behavior of the power is better handled, this form of voltage controller allows operators to reduce the generator need in particular applications. Another approach is to utilize a ‘Close Before Excitation’ system, which closes the breaker as soon as the engine starts running.
This allows for a progressive increase in excitation as the engine speed increases, allowing for a very soft start of loads linked to the baseload generator. This is particularly helpful for magnetizing step-up transformers in medium-voltage applications. As a result, buying larger generators than required to deal with the first electrical surge is no longer essential. Furthermore, clever regulation of the generator’s voltage can result in decreased fuel usage, cheaper maintenance costs, and longer generation lives.