HVAC and Electrical Fundamentals
Last Updated on Thursday, 12 November 2009 01:35 Written by Richard Friday, 12 December 2008 05:33
HVAC and Electrical Fundamentals
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Electricity is usually produced by a generator at a power station and delivered to sub-stations for distribution to homes and businesses. Electricity can also be produced using chemicals like the chemical processes produced in batteries. There is also static electricity which is generally produced from friction and is often times uncontrollable like lightening. Either way electricity is produced; modern society has come to rely on electricity in everyday life. Without electricity it is fair to say many people in modern society would find life miserable and difficult. Electricity powers our cell phones, lights, refrigerators, air conditioners, heaters, and without electricity cars would not be around as electrical energy is needed in the combustion process. The most common ways electricity is generated is the chemical process such as in batteries and generators using magnetism to produce electricity.
Electrical Flow
Electricity is delivered to it's destination via wires (conductors) or in electronics, semi-conductors. Electricity is a series of electrons moving through the conductor or semi-conductor at a specific potential or pressure which is referred to as voltage or electro-motive force.
Electrical Delivery
Voltage delivered from power stations generally ranges in the plus 10,000 volts range. It is generated at such a high voltage because it must travel long distances to reach its destination. The destination is usually a sub-station where a step down transformer steps the voltage down to around 7,500 volts. The sub-station has distribution lines which then feed neighbors, shopping areas, and industrial areas. When the 7,500 volts reaches the neighborhood it encounters another step down transformer that steps the voltage down again depending on the use. A residential area will have 7,500 volt to 240 volt step down transformers while shopping, commercial, and industrial areas will have 7,500 volt to 480 volt step down transformers.
Electrical Current
While voltage is one way of measuring electricity another way of measuring electricity is by measuring electrical current. Electrical current is a measure of the amount of electrons flowing through a circuit. If an electric motor is running electrons are flowing through the circuit and this can be measured as current or current is generally referred to as amperage or amp draw in the circuit. If you was measuring current in the circuit with an electric motor and you turned the switch off to the motor the current or amp draw would go to zero. While potential or voltage still exists in the circuit the current is zero with the motor turned off.
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Electrical Current, Resistance and Voltage Defined
Think of current and voltage in the form of a faucet at a sink. If you open the faucet the water flows at a certain rate. Say the water flows at 1 gallon per minute. It that was electricity we would call that flow rate amp draw or current. The pressure coming from the faucet would be referred to as voltage. The friction the water encounters from moving through the pipe would be referred to as resistance. Make the pipe smaller with the same pressure (voltage) and the resistance or friction increases. Make the pipe larger with the same pressure (voltage) and the resistance or friction decreases. Turn the faucet off and you still have pressure (voltage) but no flow or current. The same can be applied to electricity as water flowing from that faucet. Simply compare flow of the water, pressure of the water, and resistance of the water pipe to current, voltage, and resistance of the wire and load and you will understand these terms better and how they work in an electrical circuit.
Direct Current (D.C.) and Alternating Current (A.C.)
A direct current circuit has the flow of electrons in one direction and uses only half the sine wave while alternating current flows in both directions in the circuit and uses the full range of the sine wave depending on its frequency or wavelength. Direct current is generally produced by batteries but can be produced by a D.C. generator or a rectifier which converts A.C. to D.C. using diodes. Alternating current is produced by a generator or by converting D.C. to A.C. using a converter. Alternating current in the United States at 60 hertz and most of the rest of the world runs on 50 Hertz. Hertz is a way of measuring the frequency of electricity.
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Happy New Year to you Richard and a Happy Website Experience.
Regards