Converting kilowatts to horsepower: how many HP are in one kW + principles and methods of calculation

Horsepower and Watts. The first term is a power meter, which is becoming increasingly outdated and is gradually being replaced from electrical engineering, the second is modern.Motorists, however, resist, preferring clarity.

Sometimes it is necessary to translate “l. With." in watts - let's figure out how they relate.

What is horsepower?

The only measure of power whose equivalent is recognized throughout the world is the kilowatt. Nevertheless, despite this, where there are internal combustion engines, their power is indicated in horsepower. This unit is also popular when calculating transport tax.

For this reason, owners of their own transport have to transfer kilowatts to this off-system unit.

The expression has firmly entered the lexicon since James Watt from Scotland introduced the first steam engine to replace horse traction at the end of the 17th century.

Horsepower, as a term, a meter, allowed the average person to visualize how many horses are replaced by a machine

Interesting fact: at one time in France, or rather in Paris, there were standards for the draft force of crews (omnibuses).

According to them, a horse harnessed to a carriage must run 55.056 km daily in a working day of 5 and a half hours and a draft force of 25.8 kg. The power developed by the horses was 72.kgm/s.

The power value in France is almost identical to what was obtained in England. The French unit was called Cheval vapeur. Literally translated it sounds like “steam horse”

Observing the work of a horse lifting a load from a shaft, he found that at a constant speed of 1 m/s it lifts a load weighing approximately 75 kg.

Through calculations, James Watt defined horsepower as the power at which a horse can lift a load weighing 250 kg to a height of 30 cm in 1 s. Therefore, 1 hp. =75 kgm/s, and if in watts, then - 735.499 watts.

Following this, the following horsepower options came into use:

• electrical;
• mechanical;
• indicator;
• boilers and many others.

Since the definition of horsepower is ambiguous, in order to bring order to this issue, in 1882 the English Association of Engineers at its congress approved a previously unknown unit of measurement of power. It was named after the inventor - W (watt) or W, and it became international.

Later, the adoption of SI required that motor power be denoted in kilowatts. The unit began to be used in technical documentation and advertising brochures. To finally put an end to the outdated concept, in 2010 an EU directive prohibited the use of horsepower without duplicating it in kilowatts.

James Watt, when he introduced the concept of horsepower, simply sought to show the advantages of using machines instead of animals. He did this by calculating the amount of energy expended by the horse and the mechanism when lifting a load.

Different types of horsepower are related to watts as follows:

• electric - 746 W;
• mechanical - 745.699871582 W;
• metric - 735.4988 W;
• indicator - 745.6998715822 W;
• boiler - 9809.5 W.

European countries mainly use metric horsepower. By it we mean the power used to lift a weight of 75 kg upward at the same speed and generally accepted acceleration g = 9.80665 m/s².

In the US and UK, in the automotive industry, horsepower is equal to 1.0138696789 metric hp. or 745.6998815 W. Boiler, electric hp also used in America.

While a metric unit is equal to 0.74 kW, when defined in feet and pounds, it is associated with the movement of a 1 pound load over 33,000 feet in 1 minute or 1 pound over a distance of 550 feet in 1 second.

The unit “horsepower” has been removed from official circulation in Russia. When calculating transport tax, the metric variety of hp. still applies. In this case, the tax amount is multiplied by the number of hp.

Units of measurement: watts and kilowatts

The unit of power, watt, is included in the SI system. One watt is 1 joule of work done in 1 second.

This measure of power can also be expressed through the ratio of other units:

1. Newton moved 1 m in 1 s.
2. One kilogram moved 1 m in a second.
3. Volt-Ampere

One kilowatt contains 1000 watts. This unit is used to measure the energy of sound, heat, current power, and radiation fluxes.

Ways to convert kilowatts to hp. With.

The mutual transition of these two units can be accomplished by several methods:

1. Online convectors. There are software products for this, but you need network access. If you have the Internet, then the method is very fast and simple.
2. Tables. They contain values ​​that occur more often than others.
3. Formulas for translation. Used to “convert” physical quantities manually.
   

Numerical values ​​used in practice: 1 kW = 1.36 hp, 1 hp. = 0.735 kW. It is easier to work with the first expression, and to simplify, 1.36 is rounded to 1.4. The error is small and if we estimate the power approximately, then its value can be neglected.

The way in which power was determined in fact influences the amount of power obtained when converting from one value to another

Almost converting kW to hp. will have the following form:

90 kW x 1.4 = 126 hp and reverse action: 140 hp. : 1.4 = 100 kW.

For more accurate calculations in order to determine how many horsepower there are in a kilowatt, a coefficient of 1.35962162 is used.

Horsepower in a car

The value in kW divided by 0.735 is the horsepower in the car. It is comparable to the action performed in 1 s in order to lift a 75 kg load by 1 m. In this case, gravity is also taken into account.

The greater the power of a car engine in relation to the weight of the vehicle, the more efficient it is. In other words, the less the body weighs, the greater the power indicator and the greater the acceleration of the car.

In order to transform the rated power of a certain car from kilowatts into horsepower, you need to divide the existing value by 0.735

For example, the Jeep Wrangler has 177 hp. and a total weight of 2.505 tons. The ratio of power to total weight will be: 177: 2505 = 70.56. Acceleration to hundreds of kilometers per hour - 10.1 s.

If you take a powerful Ferrari 355 F1 car with a 375 hp engine. and weighing 2.9 tons, then the ratio will be 375: 2900 = 0.129. Acceleration to 100 km/h is 4.6 seconds.

This is a table with which you can very easily transform horsepower into kilowatts without any calculations

The designation for horsepower varies from country to country. While in Russia it is hp, in English-speaking countries it is hp, in the Netherlands it is pk, in Germany it is PS, in France it is CV.

When the kilowatt was introduced, France stopped using CVs and completely switched tax calculations to these new units of power. In the UK, the car's dimensions are used as the basis for vehicle tax.

In Russia, in addition to transport tax, hp. used when calculating the amount of payment when insuring an iron “horse” (OSAGO). HP is used. and when determining the actual power of a car engine. At the same time, terms such as gross and net are in use.

The first indicator is measured on a stand and the operation of the cooling pump, generator and other related systems is not taken into account. Its value is always higher than the second parameter, but does not reflect the power generated under normal circumstances.

If you use this method to convert the kilowatts indicated in the passport, then only the amount of motor work will be determined. To accurately estimate its power, it is impractical to use this method due to the large error, which ranges from 10 to 25%. Since the engine performance will be overestimated, the transport tax will also be high.

The stand provides a net value taking into account auxiliary systems. The parameter obtained in this way more accurately corresponds to the power under normal conditions. A device such as a dynamometer can determine power even more accurately.

The more horsepower the engine in a car has, the more tax the owner of the vehicle must pay, so every motorist must be able to convert power from kW to hp. and vice versa

On how much hp How the car's engine accelerates depends on the class of the car and its dynamic characteristics.

If there is no technical documentation for the car, but you need to know its power, you can do this using two methods.

#1: Method for determining car power

To determine power in traditional horsepower using this option, quantities such as torque and engine speed are needed. You can find them in the instructions or on the Internet if you indicate the appropriate make of car.

Next, the found parameters are multiplied. The following expression is used for calculation:

(RPM x T) / 5252=HP

In it, RPM is the engine speed, T is the torque, 5.252 is the number of radians per second. So, one of the Hyundai Santa Fe car models has a torque of 227 at a speed of 4000, so 227 x 4000 = 908,000. The result is divided by 5252 and the power is obtained in horsepower:

908,000: 5252 = 173 hp

#2: Power calculation method

On a car engine, voltage is usually indicated in volts, current in amperes, and efficiency in percent.

Using this data, the engine power in hp is calculated. according to the formula:

(V x I x efficiency) : 746=HP

Efficiency is converted to a decimal fraction - 82% as a decimal fraction.

Voltage, current, efficiency are multiplied, then the result is divided by 746. So, if the voltage is 240 V, the current is 5 A, the efficiency is 82%, then the power is in hp. will be 1.32 hp.

Conclusions and useful video on the topic

Horsepower details:

Increasingly, the amount of power is indicated in kilowatts, and non-system units are becoming a thing of the past. Yet the need for horsepower conversion still exists. While these units exist, one must be able to use them competently.

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