MECH311 Self Study Course.pdf - Fundamentals of Motors 5/05...

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Fundamentals of Motors 5/05 FOM
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Fundamentals of Motors Fundamentals of Motors 1-1 FOM Table of Contents Electrical and Magnetic Basics 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fluid Flow versus Electron Flow 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electro Magnetism 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single and Three Phase Power 1-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Torque, Horsepower and Speed 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Torque 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Speed 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Horsepower 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relationship of Torque, Speed and Horsepower 1-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NEMA 1-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Speed versus Torque and Current 1-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motor Basics 1-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Size 1-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NEMA Motor Enclosures 1-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Factor and Duty Cycle 1-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Efficiency 1-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Motors 1-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Three Phase AC Motors 1-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Explosion Proof 1-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single Phase AC Motors 1-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DC Motors 1-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1-2 Fundamentals of Motors FOM Motor Fundamentals consists of four chapters: Electrical and Magnetic Basics Torque, Horsepower and Speed Motor Basics Type of Motors Electrical and Magnetic Basics Electrical motors use magnetism and induction to change electrical energy to mechanical energy. It is therefore important to understand electrical and magnetic fundamentals. Fluid Flow versus Electron Flow Electricity flows through conductors (wire) much the same as liquid flows through tubing or pipes. Electricity is measured in Amps, Volts and Watts and may be compared to liquid flow as shown in Table 1 1. There are similarities in the relationships of pressure, flow and energy. Table 1 1 Unit Fluid FLow Electrical Flow Media Water Electrons Pressure PSI (Pounds per Square Inch) Volts Flow Gallons Amps Energy Gallons per minute Watts Ohms Law In electrical circuits, the relationship between voltage (electrical pressure), current (electron flow) and resistance (resistance to electron flow) is stated as ohms law: I + E R I = Amperes (AMPS) E = Volts R = Resistance (Ohms) Therefore, if the voltage across the motor changes, either amps or ohms has also changed. Electro Magnetism Magnetism can be produced by applying electricity to a coil of wire. The wire is wrapped around an iron core. When current flows through the wire, Magnetic lines of force (called magnetic flux, from North pole to South pole) are produced, Figure 1-1. Figure 1-1 Electro Magnetism When a wire is moved through a magnetic field, electric current is produced in the wire. This is known as induction and is the principle of operation for an AC or DC motor generator. The relationship of magnetic flux and current flow in a wire (amps) is shown in Figure 1-2. Figure 1-2 Motor Generator Wire Amps Magnetic FLux Wire Movement North South
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Fundamentals of Motors 1-3 FOM When the wire is moved up through the magnetic field, electric current flows in one direction in the wire. When the wire is moved down through the magnetic field, electric current flows in the other direction. This relationship is shown in Figure 1-3. Figure 1-3 Electro Magnetic Generator Simplified Alternator: (AC Generator) The magnetic field is being moved through the wires rather than the wires moving through the magnetic field. A complete current path is established to the Light by the wires that are rotating through the magnetic field.
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