A Guide to Generator Ratings - Thompson Power Systems

Generators are an excellent way to maintain reliable power during an outage or in areas with little to no grid coverage, including remote worksites where electrical power is needed but unavailable. It’s important to understand the technical specifications of generators before you purchase one for your business to ensure you’re getting enough power for your operations.

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Generator set (genset) ratings help you make the best choice when buying a new generator. Different ratings, such as eKW and kVA, help inform buyers about the power capabilities of different generators so they can determine whether a specific model can bear the load needed for their operations.

What Is eKW?

The eKW generator rating, also written as kWe, is the total generator output after efficiency losses or the loss from mechanical to electrical energy. The generator’s electrical power is generally measured in either watts or kilowatts. It’s essential to understand the eKW of a generator since equipment and appliances directly use this electrical power while the generator is operational. Without the proper amount of electrical power, you may be unable to run all the necessary equipment or appliances for your operations.

What Is kVA?

The kVA generator rating measures apparent power, including real and reactive power. In simple terms, a kVA for a generator tells you how much power output the machinery is capable of for different operations. Reactive power differs from real power since it’s not consumed and cycles between the load and power source.

The kVA rating indicates power output, meaning the higher the rating, the more power your generator can produce. You can calculate kVA by multiplying the voltage by the amps. You can also convert kVA into eKW by multiplying by the power factor, which differs based on the phase of the generator.

How Are Generators Rated?

Apart from eKW and kVA, generators are rated using various factors. Standard generator ratings you’ll find in the industry include:

• Standby power: Standby power ratings refer to the generator’s ability to provide power during an emergency. Standby power can last between 500 hours to a full year, depending on the generator. You should look for generators with a standby power rating with a power factor of no more than 0.7.
• Prime power: Prime power ratings refer to the generator’s capability to provide power for an unlimited time frame on varying loads. However, overloading can be accommodated, but this is limited to only once every twelve hours and at 10% of the rated value. The overload limit should also not exceed more than 25 hours annually.
• Continuous power: The continuous power rating refers to the generator’s ability to provide power for unlimited time frames to a continuous load. The output can range between 70% to 100% of the rated power output. The load should remain steady with little variation, and no overload capacity with continuous power exists. It’s essential to note that operating above the suggested rating will affect the life span and engine costs annually.
• Limited time power: Limited time power ratings allow you to use generators alongside a given utility. Generators can run with limited time power for up to 500 hours per year. However, there are no capabilities for overload capacity when using limited time power.
• Load factor: The load factor rating measures the generator’s efficiency of electrical usage. For example, a generator with a higher load factor uses the electrical system more efficiently. The load factor is calculated by multiplying the operating time or time at a specific load by the specific or rated load.

Look at each of these ratings when comparing generators to find the best system for your operations. Some generators will be more suited to your applications than others, so it’s essential to understand the differences between each rating to make the best choice for your business.

What Rating of Generator Do You Need?

When choosing a generator for your applications, you must ensure it has enough capacity to provide power during peak work conditions. There are two methods you can use to determine what generator you need for your business.

1. Determine Full Load Capacity

Calculating your full load capacity can help you determine the proper generator size to provide enough power for your applications. Follow these steps to calculate the full load capacity:

1. Take full load current measurements when your business is operating at peak usage. Find the service panel and attach ammeters to each leg of the electrical service. Once each ammeter reaches a measurement, add these numbers together to determine the total amps used. Convert the amps to kWs.
2. Once you find the total kWs for the amps, you’ll want to divide by two for single-phase currents or three for three-phase currents. Afterward, multiply the remaining number by the supply voltage and by 1,000 for the kW required.
3. Find the kWs of your emergency systems use and add them to your remaining number to obtain the full load kWs.

Using the full load kWs, you can determine the full load capacity of your applications, allowing you to purchase the proper generator to meet the power needs of your business. Calculating full load capacity is an excellent way to ensure you choose the right generator rating, especially if you have more complex work environments that are frequently changing.

2. Measure Square Footage

If you run a simpler operation, such as a retail store or a business that operates out of a single building, and you use the same amount of energy consistently, you can calculate what size generator you need based on square footage.

Generally, you’ll want to start with 50 kilowatts to power and add 10 kilowatts for every square foot for retail and five kilowatts for commercial applications. For example, if your business is 500 square feet, you would multiply 500 by 5 to get 2,500. Finally, you’d add 50 for 2,550. You’d want to look for a generator with kW ratings at or above 2,500 to ensure you have enough electrical energy to power your business. You can also consult a power systems specialist for professional advice about the best generator for your business.

Contact Thompson Power Systems to Rent or Buy a Commercial Generator

If you’re looking for an effective power solution for emergencies or remote work, Thompson Power Systems has you covered. We offer new, used, and rental generators to meet the needs of your applications, whether you need a system to keep your business operational during an outage or to sustain power for critical systems.

Commercial generators are available in different voltage ranges. They are classified into three main categories: low, medium, and high-voltage commercial generators. Adding to these are quite uncommon yet useful commercial generators with extra high and ultra-high voltage. Wondering about the range of each? They vary. Why and how they vary is covered in the article. Read on to enlighten yourself and make sound decisions on your next purchase. 

High, Low, and Medium Voltage Classification Differences 

The voltage classification varies among the countries. In the US, the National Electrical Code and National Electrical Manufacturers Association are concerned with voltage classification through guidelines and standards. The ANSI, or American National Standards Institute, is concerned with the generation of guidelines and standards for businesses across different industries. 

ANSI

The Electrical Engineering Portal offered a breakdown of ANSI standards, which indicate the following classification:

Maximum: 1,100,000 VAC

Maximum: 69,000 VAC

Maximum: 600 VAC

NEC

Comparing the ANSI standards with NEC standards, the classification has been brought forward by Generac in their white paper. It states: 

Maximum: Volts

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Maximum: Volts

Maximum: 49 Volts

Practical Usage

Going further into the differences, the commonly used voltage distribution across the industries are 

• 480 VAC
• VAC
• 12,470 VAC
• 13,800 VAC

Generac mentions generators with less than or equal to 600 Volts are medium voltage generators, while the ones with more than 600 volts are high voltage generators. Therefore, the voltage classification depends on the governing authority. 

Types of High Voltages 

As mentioned in the ANSI code, there are High, Extra-High, and Ultra-High voltages. Concerned with increasing the efficiency, the breakdown of the voltage range of each is as follows: 

Maximum: 2,30,000 VAC

Maximum: 7,65,000 VAC

Maximum: 1,100,000 VAC

Types of Voltages 

Besides the low, medium and high voltages, the generators will also exhibit a few other values of voltages. These are specific to the generator and indicate information about the voltage requirements and production of the generator. Here is a brief about them:

Rated voltage: It is the maximum and safe voltage generated by the commercial generator. 

Nominal voltage: It is the predetermined production voltage for any generator. 

Industry-Based Usage of Voltages 

Different industries require different voltage-based generators depending on the requirements. Here is the breakdown for you: 

Low Voltage Commercial Generators: They are commonly found in private homes, retail establishments, and small businesses. The power requirements here are a few to several hundred kilowatts, and voltage requirements are around 480. 

Medium Voltage Commercial Generators: The generators with the stated type of rating are used in data centers, commercial and industrial facilities, institutes, and the healthcare industry. The power requirements here vary from several hundred kilowatts to a few megawatts. The required voltage levels are 480 to 15,000 volts. 

High Voltage Commercial Generators: Their usage is witnessed in heavy industries such as manufacturing plants and utility-scale power generating facilities. The power requirements here lie between several megawatts to tens or hundreds of megawatts. The voltage levels here exceed 15,000 volts. 

Check Voltage Based Generator Availability at CS Diesel

With the information on voltage classification, you will be able to identify the voltage rating of your owned generator. The information is important to decide the servicing rightly, get and validate the equipment type or parts being used and replace the generator with ease if required. You can now also compare the currently possessed generator with the currently available ones in the market for the same voltage rating. It is necessary to obtain the maximum efficiency for the used equipment. Offering you a wide variety based on voltage and many other criteria, CS Diesel Generators brings you a myriad of choices! 

Common Questions About Voltage in Commercial Generators

Q1. What type of voltage is provided by the generators?

The generators are capable of providing both AC and DC voltages. However, AC voltage generators are more common compared to DC voltage generators. 

Q2. Are generators and alternators the same?

No, the generators are concerned with the conversion of mechanical to electrical energy. The alternators perform the action of converting mechanical energy into AC electrical energy. 

Q3. What are the essential factors to consider when determining the required voltage generator?

Besides contacting the professional, the important factors to consider are the voltage required on-premises, the maximum current rating to operate the devices, starting current requirements for industrial motors, and the utility frequency. 

Q4. How to calculate the output required from the commercial generator?

The power requirement from a commercial generator will be obtained by using the following formula: Power = Voltage * Current. 

Q5. What voltage range of commercial generators are available at CS Diesel?

You can apply the different filters to choose your required type of voltage. The options for choice include: 

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