Power An Introduction

Power  Learning Standard  ENGR-EP-1. Students will utilize the ideas of energy, work, power, and force to explain how systems convert, control, transmit, and/or store energy and power

Power  Concepts  Identify the difference between work and power  Define power  Identify the basic power systems  List the elements of all power systems  Define horsepower (hp)  Recognize the various power components in electrical circuits and fluid circuits  Summarize the advantages and disadvantages of various forms of power

Power  Concepts  Describe various forms of power for specific applications  Diagram the basic power components in an electrical circuit and fluid circuit  Calculate the efficiency of power systems and conversion devices  Compute power and horsepower for various forms of power

Power  Vocabulary

Power  Power: Introduction  Power is needed in our technological society. Without it, our society would not exist

Power  Work vs. Power  Work is the application of force that moves an object a certain distance.  Power is the rate at which work is performed or energy is expended.

Power  Power System  When energy is harnessed, converted, transmitted, and controlled to perform useful work, this is call a power system  There are three types of power systems:  Electrical Systems  Mechanical Systems  Fluid Systems

Power  Electrical Systems  Electrical systems are power systems that use electrical energy to do work. The most common electrical power components include switches which control the flow of electricity within the system, fuses or circuit breakers for protecting the electrical circuitry, wires for transmitting electricity, and loads for utilizing the electricity.

Power  Mechanical Systems  Mechanical systems are power systems that use mechanical energy to do work. Machines are devices used to manage mechanical power  Six simple machines are used to control and change mechanical power  The lever  The pulley  The wheel and axle  The inclined plane  The wedge  The screw

Power  Fluid Systems  Fluid systems perform work using the energy created by liquids and gases. Fluid power can accomplish the movement of very heavy objects. Fluid power components consist of valves, hoses, air compressors or hydraulic pumps, cylinders, and motors.  Two types of fluid systems  Pneumatic systems  Hydraulic systems

Power  Characteristics of Power Systems  Power systems come in various sizes and perform a wide variety of tasks. Power can be produced by three forms: electrical, mechanical, or fluid. In any of these three forms, power is comprised of two basic, measurable characteristics: effort and rate

Power  Effort  Effort is the force behind movement in a power system  In linear mechanical power, effort is usually known as force and is usually measured in pounds. In rotary mechanical power, the term for effort is torque. Torque is a twisting or turning force and is measured in foot-pounds  In fluid power, effort is referred to as pressure. It is usually measured in pounds per square inch  In electrical power, the effort behind the movement of electrons is called voltage. It is usually measure in volts

Power  Rate  Rate is the characteristic of power that expresses a certain quantity per unit of time. Regardless of the unit of measure, all rate characteristics include both a quantity and a time element. As quantity increase over time, a greater amount of work can be preformed  In electrical power, the measurement for rate of flow is the ampere  In mechanical power, the measurement is either revolutions per minute or feet per minute  In fluid power, the most common measurement is gallons per minute

Power  Basic Elements of Power Systems  Energy Source: Required for all power systems to function  Conversion Method: Necessary to convert the energy so some type of work is produced  Transmission Path: Needed to move energy to the point where it is supposed to produce work  Storage Medium: Necessary when power must be stored for use at a later point in time  Protection Devices: Shields components in power circuitry from excessive effort or rate of flow

Power  Basic Elements of Power Systems  Advantage-Gaining Devices: Modify the effort and rate characteristics of power in order to achieve a goal  Control System: Needed to control the power within the system  Measuring Devices: Required in power systems and provide a source of feedback to monitor how well the system is functioning  Load: Output, the final goal of the power system

Power  Calculations of Power Systems  The power available in a system can be measured or calculated for each form of power – electricity, fluidics, or mechanical  The ability to measure power is important because it gives feedback to the operator on how the system is functioning or the cost at which the system is functioning

Power  Work  Work is the force times the distance through which the force acts. W = Fd

 Work  A rider in a canoe weighs 120 lbs. How much work is being done, if the canoe is paddled 600 ft.?  If 2000 lbs. have to be moved 30 ft., how much work has to be done?  On a recent adventure trip, Anita went rock-climbing. Anita was able to steadily lift her 150 lbs. body 60.0 ft. How much work did she do?  Bart runs up a 6.0 ft. high flight of stairs at a constant speed. If Bart's mass is 165 lbs., determine the work which he did. Power

 Power  Power is the amount of work performed over time. P = W/t

 Power  If a crane operator is going to move a 1000 lb. barrel of nails up 40 ft. to a fourth story window in 30 seconds, how much power is developed?  A physics teacher owns a family of squirrels. The squirrels have been trained to do push-ups in repetitive fashion. Being connected to an electrical generator, their ongoing exercise is used to help power the home. There are 23 squirrels in the family and their average mass is 1.07 lbs. They do work on the "up" part of the push-up, raising their body an average distance of 5.0 inches. If the squirrels averages 71 push-ups per minute, then determine the total amount of work done in one minute and the power generated by their activity. Power

 Efficiency  Efficiency is the relationship between input energy, or power, and output energy, or power Power X 100 Output Input

 Efficiency  Efficiency is the relationship between input energy, or power, and output energy, or power Power X 100 Output Input

 Efficiency  Input Voltage: 120V  Output Voltage: 240 V  Input Amperage: 20 A  Output Amperage: 8.7A  What is the efficiency of the electrical system?  Drive Gear Input: 20 ft.-lbs.  Input Torque 100 rpm  Drive Gear Output: 9.7 ft.-lbs.  Output Torque 200 rpm  What is the efficiency of the mechanical system? Power

 Horsepower  Horsepower is one standard measuring unit of power. The energy needed to lift 33,000 lbs. 1 ft. in 1 min. Power W t x 33,000 hp =

 Horsepower  If 200 lbs. are lifted 165 ft. in 1 minute, how much horsepower is developed?  If 380 lbs. is moved 350 ft. in 1 minute, how much horsepower is developed? Power

 Measurement Conversion  Two measuring systems are used in the U.S., U.S. customary and SI metric. It is important to know how to convert these measurements from one system to another Power

 Measurement Conversion Power