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Category: Blog
Date: June 17, 2021

When you are buying a new or used diesel generator for sale, it is widely recommended that you look at generator ratings. Now, if you are not well-versed in the ratings, all those numbers might seem a bit confusing. But to make the right choice, you would need to understand them correctly to make the right decision.

What are Generator Ratings?

It would help to start by understanding the basic definition of generator ratings. Generator rating can be defined as a set of specified values for a particular generator model by its manufacturers. It signifies the capability of delivering that much power output under normal working conditions. They are usually expressed in units like Kilowatts (kW) or Kilovolts Ampere (kVA). More on that later. Let us now look at why it is important to have ratings in the first place.

Why Do We Need Generator Ratings?

As with every product, ratings prove helpful when it comes to buying the product. Not only does it help you to understand the capability of the machine, but it also helps you to determine your specific demand. This is the reason why it is important that you understand the generator ratings.

You would find companies offering 10 kVA generator hire, 20 kW or 1000 kVA generator rental. So, you need to understand what the ratings mean? Well, these units express the power generation capacity of the generator.

Kilo Volt Amperes or kVA is conventionally used for all energy supplying devices, including UPS and transformers. Sometimes Kilowatt or kW is also used. Kilowatt (kW) represents real power whereas Kilo Volt Amperes (kVA) represents the apparent power output of the device.

What is the Difference between KW and eKW?

At Al-Bahar, we offer a wide range of Cat® Generator sets. You will find that in some cases, especially for gas-powered generators, the unit ‘eKW’ is used to express the power output. KW is the unit expressing the mechanical power driving the generator. This is the reason why it is also called as ‘Kilowatt (mechanical)’

On the other hand, eKW is called ‘Kilowatt (electrical)’. This is used to measure the actual generator output, minus the conversion loss from Mechanical to Electrical Energy. When eKW is mentioned, that is the full capacity available as electrical power.

What is the Power Factor?

Power Factor (P.F.) might not be often stated by the manufacturer, but it is important for understanding the actual performance of the generator. It might be a bit complicated to understand for the uninitiated, but generally it refers to the out-of-phase relationship between the voltage and the current in the electrical system.

In most cases, three-phase circuits will assume a Power Factor of 0.8 lagging. Of course, there might be exceptions. But, if you don’t know the Power Factor, you can assume the power factor of 0.8.

How to Convert between the Two Units?

To convert from kVA to KW, and vice-versa, the following formula can be used

(P.F) * (kVA) = (kW)

Where (P.F) is the Power Factor.

If you want to calculate the kVA, then you can use this formula.

(I x V)/1000 = kVA

Where (I) is the current, measured in Amperes and (V) is the voltage.

Just like that, if you want to calculate the current (in Amperes), you can just calculate it as follows:

(KVA x 1000)/V = I

What are the Different Standard Ratings for Generators?

Let us now understand the different standard ratings. The following are the commonly used ratings in the industry.

Standby Power Rating

The first is Standby Power Rating. This signifies the capability of the generator to provide emergency power. The duration can last from 500 hours to an entire year. The power factor for standby power rating should not be more than 0.7.

Prime Power Rating

Prime rated power is capable of providing the power for an unlimited amount of time to a varying load. Overloading can be accommodated but only at ten percent of the rated value and that is also permitted for only once in twelve hours.

Continuous Power Rating

In case of this rating, the generator can provide a power supply for an unlimited period but only to a non-varying, or continuous load. In most cases, the average output comes at around 70 percent to as much as 100 percent of the rated power output.

The major condition is that load should be relatively steady. There should be no significant variations in it. At the same time, there is no overload capability.

Limited Time Power Rating

If you apply a prime rated generator to limited power ratings, then you can use it in parallel with the utility. It can also run for a duration of five hundred hours in a year. Unlike prime rating, you get no provisions for overload capability.

At Al-Bahar, we offer exclusive range of Cat generators for sale and rent. You can buy new or used generators that deliver the required power for your operations. Our team would help you choose the right generator based on your requirements. Visit our product page for diesel generators for sale or contact us today to know more