Mechanical and Electrical Systems PDF

MECHANICAL AND ELECTRICAL SYSTEMS BU II (Electrical & Mechanical Systems) is about building utility systems which involves Electrical and Mechanical Systems. It is a study of specialization, which concentrates on the study of the supply of electricity and installation of mechanical equipment in the...

MECHANICAL AND ELECTRICAL SYSTEMS BU II (Electrical & Mechanical Systems) is about building utility systems which involves Electrical and Mechanical Systems. It is a study of specialization, which concentrates on the study of the supply of electricity and installation of mechanical equipment in the buildings. It is one of the most important aspects in building design and technology. Electricity Form of energy generated by friction, induction, or chemical change, having a magnetic or radiant effect. fundamental nature of all matter is electrical William Gilbert the Father of Electricity describes “electrification of many matters”. Electricity can be found in nature: Static Discharge (electric charge at rest) Electromagnetic radiation from the sun Lightning Galvanic cells (pipe corrosion) PRODUCTION OF ELECTRICITY Turbines and generators are basic components that generate electricity. Turbine is a rotary engine that changes the force of water, fuel, and wind into mechanical energy capable of rotating that shaft which is connected to a generator. A generator is a machine used to change the mechanical energy into electrical energy Turbines that produce mechanical energy: Water-driven turbines – run through water force Steam-driven turbines –heat energy into mechanical energy through steam Nuclear-reactor turbines Other electrical producing equipment/alternative sources: Internal combustion engines (ICE)- Identical to the engine of the automobile in which the shaft rotates to produce electricity. Invented by Rudolf Diesel the diesel engine was named after him. Wind Turbine- Converts the power of the wind into electrical power. It requires 10 miles per hour of wind to operate properly. Solar Photovoltaic cells- Sun’s power to produce electricity by means of a silicon wafer with a small amount of arsenic. The wafer is treated with boron gas. The contact between the wafer and the modified gas zone produces voltage which flows by the action of sunlight. These are connected to batteries to store the energy. ELECTRICAL TERMS AND ELECTRICAL UNITS: Ions – an atom or molecule not electrically balanced Volt/Voltage – electrical pressure that causes the electrons to move through a conductor (electromotive force / EMF) Ampere – the standard unit of measuring the strength of the electrical current Watt – rate or measurement of power used or consumed Ampere-Hour (Ah) - A unit of measure for battery capacity. It is obtained by multiplying the current (in amperes) by the time (in hours) during which the current flows. Capacitor - A device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator. Circuit - A closed path in which electrons from a voltage or current source flow. Circuits can be in series, parallel, or in any combination of the two. Circuit Breaker - An automatic device for stopping the flow of current in an electric circuit. Current - The flow of an electric charge through a conductor. An electric current can be compared to the flow of water in a pipe. Measured in amperes. Frequency - Number of cycles per second, measured in hertz. Inductor - A coil of wire wrapped around an iron core. The inductance is directly proportional to the number of turns in the coil. Insulator - Any material where the electric current does not flow freely. Insulative materials, such as glass, rubber, air, and many plastics have a relatively high resistance. Insulators protect equipment and life from electric shock. Inverter - An apparatus that converts direct current into alternating current. Kilowatt-hour (kWh) - The product of power in kW and time in hours. Kllowatt-hour Meter - A device used to measure electrical energy use. Kilowatt (kW) - Equal to 1000 watts. Waveform - A graphical representation of electrical cycles that shows the amount of variation in amplitude over some period of time Electric Current can be classified as: Direct Current (DC) - DC flows in one direction, from negative to positive - DC is produced by a DC generator and is utilized for special equipment requiring exact revolutions per minute (RPM) for proper operation. - Small quantities are produced by batteries or by rectifiers. - Usually used for emergency lighting, communications, signals, and control equipment, etc. such as elevators, rapid transit propulsion systems, vehicles, electro-chemical processing, printing press drives, electroplating, motors and compressors in HVAC/  Alternating Current (AC) - Reverses its direction of flow - Found in transmission lines - AC is produced by an AC generator which is commonly referred to as an alternator. - The advocator of AC Electricity is George Westinghouse - Alternating current reverses its polarity and reverses its direction of flow on each alternation - Increased voltage has low power loss, lower voltage drops, and more economical to construct George Simon Ohm – German Scientist in 1926 who discovered the relationship between the current, voltage and resistance Ohm’s Law States that “when a current (I) flows through a circuit with given resistance (R), is directly proportional to voltage (V)”