Having knowledge about electricity is fundamental for refrigerists do their job, without causing problems for the equipment and components, and without generating risks for your own safety. We explain about following four key-concepts within this area.
Let's start with electric tension, which is also called voltage. Its unit of measure is in volt, represented by the letter V.
All electrical appliances are designed to operate at a certain voltage or voltage range: 110V, 115V, 115-127V or 220V. This value, specified by the manufacturer, is called nominal tension.
There is also the nominal supply voltage, which is the one provided by electric energy’s companies. There are many variations of this tension, which could harm the equipments. This variation often occurs at peak times of consumption.
The refrigerators, in general, support the fluctuations in the electric network well. Embraco compressors are designed to withstand a large voltage fluctuation in the power grid, in some cases being possible to start at 100V, for compressors with a nominal voltage of 220V.
To know the tension, use the voltmeter. This instrument, which should be part of the tool kit for refrigerists, is always connected in parallel to the points between which the voltage is to be measured.
The current is the amount of electrical energy that goes through the circuits and appliances, driven by wires and electric cables. The unit of measure of the electric current is Amp, represented by the letter A.
Two types of current exist:
· Continuous current, recognized by CC or DC (from the English, direct current);
· Alternate current - CA or AC (from alternating current).
The current continues to flow in only one direction. This is what happens with batteries, where the current will always occur from the negative pole to the positive pole.
An alternating current constantly changes direction, reversing polarity with each cycle. A complete cycle takes the current from zero to the maximum value in one direction, decreases to zero, then repeats the same phenomenon in the opposite direction. In the Embraco compressor labels, the symbol "~" stands for alternating current.
According to the country, the alternating current of the electrical network may have a different frequency, that is, a different number of complete cycles completed every second. It can be 50 cycles per second (50Hz) or 60 cycles per second (60Hz).
To measure the electrical current, use the anmeter. This is the other instrument which the refrigerist must have, always remembering that it should be connected in series of the circuit.
The electrical resistance is the capacity of one material body to oppose the flow of the current which indicates the difficulty that electrical current has in flowing through the current. Thus, for the same voltage, the higher the resistance, the less electrical current will pass.
Several factors contribute to the resistance: the composition of the materials, their length, cross section and temperature. Maximum strength is obtained with the use of insulating or dielectric materials such as glass, porcelain, rubber and certain synthetic materials. Metals such as copper and aluminum are good conductors of electric current, presenting little resistance to the passage of current. Because of this, they are used in fibers, electric cables and compressor motors.
The device popularly called "resistance", present in showers and other devices, is actually called a resistor. It is used for transforming electric energy into heat (thermic energy).
The electrical resistance has ohm as a unit of measure, symbolized by the Greek letter, omega (Ω). It is measured by the ohmmeter, which is often part of a multi-tester apparatus. In refrigeration, this instrument is used to measure the resistance of motor coils and resistors, as well as to detect problems of continuity (interrupted circuit or not) of the wires between switches, thermostat and other components.
In order to measure the resistance of any compressor or equipment, it must be switched off and the current passing through it will be equal to zero. The measurement is made between two points: for example, between the terminals of the starting and operating coils.
Electrical power indicates the electrical work performed by an appliance during a certain period of time. This electrical work involves the transformation of electric energy into another type of energy (mechanical for example) occurring whenever an electric voltage drives electrical charges through a conductor.
In a refrigerator, the electric energy is transformed into mechanical energy by powering the compressor motor. In turn, the compressor uses mechanical energy to circulate refrigerant fluid, transferring the heat from inside the cabinet to the outside.
The unit of measure of electrical power is in watt, represented by the letter W. In general, every electric appliance informs the power that it will use, defined in its design (the so-called nominal power).
In light bulbs, for example, we find specifications such as 120V and 60W, which indicate that it must be connected at 120 volts to consume 60 watts of power. If it is connected to a 220 volt source, the lamp will dissipate much more than the specified 60 watts and it will burn. On the other hand, if it is connected to a source less than 120 volts, it will dissipate less power, providing weaker illumination.
To measure the power being consumed by equipment and devices, the wattmeter is used. This measurement is important for:
· Check if they are connected properly and take advantage of the power for which they were designed for;
· Evaluate them to make sure that they are working under ideal conditions;
· See if the components used in the connection conform to the manufacturer's specifications (for example, the wire gauge diameter).
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