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··· ELECTRIC POWER
Is the speed at which electric energy is consumed or generated. It is measured in watts per second.
··· EFFECTIVE POWER
The effective power is that which is specified on all electric receivers, which are devices that use electricity to carry out work.
The concept of effective power goes back to the beginnings of electricity, when direct current began to coexist with alternating current.
When Nikola Tesla discovered alternating current, direct current already existed. Edison had an electricity company which distributed and sold direct current.
It is a well-known fact that the disagreements between Edison and Tesla with regard to the differences between direct and alternating current were truly ferocious and, although this is not the time to expand on them, it is useful to point out that in order to compare both currents, they resorted to measuring work with both.
The work consisted in heating a resistance with 110 volts of direct current and 110 volts of alternating current.
The measurement established that in order to reach the same temperature in both cases it was necessary to increase the voltage of the alternating current to 155.1 volts, which was equivalent to multiplying 110 volts by 1.41.
The alternating current power that produced the same heat as the direct current was called effective power.
Since then, it has been established that in an alternating current the effective power equals the maximum power divided by 1.41 and that the maximum power equals the effective power multiplied by 1.41, and the same has occurred with voltage and current.
Given that 1,41 =  , in the formulas ,the square root of two is used, rather than 1.41.
In alternating current one always speaks of the effective value-. When we say 220 volt alternating current we know that the maximum value is 220 x 1.41 = 310.2 volts.
··· PEAK POWER
In alternating current, peak power, also called maximum power, is the product of the maximum current and the maximum voltage.
··· START-UP POWER
It is a well known fact that, in order to start up, electric motors require a power considerably above the effective power for the duration of the start-up, normally 200 milliseconds.
Induction motors require a power 7.5 times above the effective power for start-up.
Therefore, in order to calculate the start-up power of several machines with motors, we must multiply their effective power by a number we define as start-up factor.
··· TRANSIENTS
When a motor is connected, from the moment the voltage is applied to its terminals until the motor starts turning, several microseconds go by, and during this time, the motor requires power peaks, called transients, substantially higher than the start-up power.
These peaks can reach up to 40 times its maximum average power, and can be different for each motor, depending on friction, the load to which it is subjected at start-up, the type of magnetic plate it uses, time of use, etc. These peaks cannot be calculated for the reasons explained.
All inductive loads, such as transformers, reactances, television and computer screen deflection coils, etc. also produce transients during the time between the application of voltage and the formation of the magnetic field of the coil.
These transients depend on the type of coil core and the shape of the coil.
··· ENERGY
Generally speaking, ENERGY is anything with which we can produce or change work.
Electrical energy: is the form of energy resulting from the existence of a difference in potential between two points and, as a consequence, work is produced. It is measured in watt-hours.
A watt-hour is the amount of energy generated by a generator with a power of one watt working during one hour.
It can also be defined as the amount of energy expended by a receiver with a power of one watt working during one hour.
Energy expressed in watt-hours is obtained by multiplying the power expressed in watts by the time of operation, expressed in hours.
If a machine with a power of 1 kilowatt works for one hour it will consume 1,000 watt-hours, if it works for half an hour it will consume 500 watt-hours and if it works for 15 minutes it will consume 250 watt-hours.
Let us suppose that we want to know how much energy is consumed by a 5 kilowatt electric induction motor during start-up.
We know that induction motors multiply their power by 7.5 at start-up, and we also know that start-up lasts 200 milliseconds.
During start-up the power required will be 5,000 x 7.5 = 37,500 watts.
Given that the work time is 200 milliseconds, converted into hours, it is: 0.0000556 hours.
The energy consumed is: 5,000 x 0.0000556 = 0.27778 watt-hours.
This example has served us to consider that the energy consumed by motors at start-up is insignificant and consequently we need not take it into account in the calculations for the installations.
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The design of an installation should be understood as the selection of the most adequate materials to satisfy the necessities of the user. 
