Choose the right size generator
It has been common practice to take motor and transformer starting kVA requirements as a yardstick to determine the size of a generator. This approach often results in generators being oversized for the motor running load and not based on the actual needs of the application. Moreover, it disregards other key factors that play a key role in sizing mobile generators. For instance, harmonics caused by variable frequency drives and sequential starting of motors.
When starting motors or transformers, large voltage and frequency dips can also occur if the towable generator set is not sized properly. Furthermore, other loads connected to the generator output may be more sensitive to voltage and frequency dips than the motor or motor starter, which can cause problems.
Thankfully help is at hand. Many power generators can now be equipped with solutions to overcome the extra excitation systems required in the alternator. Typically, two options are offered: permanent magnet or auxiliary winding. Both provide the generator with three times their nominal current to cover inrush peaks from the electrical motor, for a minimum duration of ten seconds, via a residuary excitation current.
In certain cases even more advanced options are available. For instance, some generators feature a digital automatic voltage regulator (D-AVR) that is specifically designed to handle the high inrush currents associated with starting motors and transformers. In specific applications, this type of voltage controller allows operators to downsize the generator requirement because the transient behaviour of the power is better managed.
Another option could be to use a “Close Before Excitation” system that closes the breaker just when engine starts to run. This enables the excitation to increase gradually as the speed of the engine does, allowing for very soft start of loads connected to the generator. This is especially useful for magnetising step up transformers in installations where medium voltage is required.
As a result, it is no longer necessary to buy larger generators than needed just to cope with the initial electrical surge upon starting. What’s more, with smart control of the generator’s voltage, it is possible to achieve lower fuel consumption, reduced maintenance cost and longer lifetimes.
As a result, it is no longer necessary to buy larger generators than needed just to cope with the initial electrical surge upon starting. What’s more, with smart control of the generator’s voltage, it is possible to achieve lower fuel consumption, reduced maintenance cost and longer lifetimes.
Do you know how to choose the right generator?
Check the new Light The Power App. This application is a power and light calculator to help you to choose the best solution for your needs.
Optimizing Generator Performance for UAE's Unique Needs
In the United Arab Emirates (UAE), selecting the appropriate generator size is crucial due to the country's rapid urbanization and industrial growth, which have led to increased demand for reliable power solutions. Factors such as high ambient temperatures and the widespread use of air conditioning systems significantly influence power requirements. Therefore, it's essential to consider these unique conditions when sizing a generator to ensure uninterrupted operations across various sectors.
Is generator capacity measured in kVA or kW?
Generator capacity is typically measured in kilovolt-amperes (kVA), representing the apparent power, which includes both active (kW) and reactive power. The actual usable power is measured in kilowatts (kW). The relationship between them is defined by the power factor (pf): kW = kVA × pf. For most generators, a standard power factor of 0.8 is assumed, meaning that a generator rated at 100 kVA would deliver 80 kW of usable power.
Why are generators rated in kVA instead of kW?
Generators are rated in kVA because this unit accounts for both active and reactive power components, providing a comprehensive measure of the total electrical load the generator can handle. This approach accommodates varying power factors in different applications, ensuring the generator can supply the necessary apparent power regardless of the load's nature.
How does the UAE's climate affect generator sizing?
The UAE's high ambient temperatures can impact a generator's performance and efficiency. Elevated temperatures may reduce a generator's power output and necessitate derating to prevent overheating. Therefore, when sizing a generator in the UAE, it's crucial to account for these climatic conditions to ensure reliable and efficient operation.
