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Motors and Motor-Driven Systems – Concept

Motors and Motor-Driven Systems – Concept. Motors Background. Present in all plants Stand-alone Motors Motor Driven Systems Fans, Pumps, Compressors Significant consumer of electricity. $$$. Great energy & cost savings potential!. Motor Types and Applications. Types of Electric Motors

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Motors and Motor-Driven Systems – Concept

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  1. Motors and Motor-Driven Systems – Concept

  2. Motors Background • Present in all plants • Stand-alone Motors • Motor Driven Systems • Fans, Pumps, Compressors • Significant consumer of electricity $$$ Great energy & cost savings potential! US DOE – Industries of the Future Workshop Series

  3. Motor Types and Applications • Types of Electric Motors • AC Induction/Asynchronous • Single-Phase • Three-Phase • AC Synchronous • DC Motors • Common Applications • Drive Motors • Pumps • Fans US DOE – Industries of the Future Workshop Series

  4. Industrial Motor Energy Usage By Application *US Industrial Motor-Driven Systems Market Assessment: Charting a Roadmap to Energy Savings for Industry US DOE – Industries of the Future Workshop Series

  5. Motor Terms • Synchronous Speed • Speed at which the stator magnetic flux rotates around the stator core at the air gap • Slip • Difference between synchronous speed and actual speed, expressed as percentage (5-20% for induction motors, 0% for synchronous motors) • Torque • Turning effort or rotary force produced on the motor output shaft • Horsepower • Unit of power equal to 745.7 watts or 33,000 foot-pounds per minute • Load Factor • Ratio of actual motor load to maximum load US DOE – Industries of the Future Workshop Series

  6. Power Factor • Caused by Inductive Loads • Total Power (kVA)2=[Real Power (kW)]2+[Reactive Power (kVAR)]2 • Improved power factor can: • Reduce utility bills (PF not penalized in ComEd service territory) • Increase capacity in electrical distribution system US DOE – Industries of the Future Workshop Series

  7. Motor Load Considerations • Constant torque: Torque required by the load to overcome friction is constant throughout the speed range. Horsepower requirement increases with speed • Common Applications: general machinery, hoists, conveyors, printing presses, etc. • Constant horsepower: Load decreases with increasing speed. As work piece diameter decreases, torque decreases, but speed increases to provide constant surface speed. • Common Applications: lathes, winders, un-winders, and metal-cutting tools • High inertia: loads associated with machines using flywheels to supply most of the operating energy • Common Applications: punch presses US DOE – Industries of the Future Workshop Series

  8. Motor Load Considerations • Variable Torque: Loads increase with speed. Horsepower requirement varies as the cube of the speed change or square of speed change with positive-displacement pumps. • Common Applications: centrifugal fan and pump loads, some mixers, positive displacement pumps and some types of extruders. • Greatest opportunities for energy savings and improved control. • Shock Loads: Loads may range from a small fraction of rated load to several hundred percent for a small fraction of the time. • Common Applications: crushers, separators, grinders, and, perhaps, conveyors, winches, and cranes • Drive has two fundamental tasks: to move the load and to protect the prime mover and driven equipment US DOE – Industries of the Future Workshop Series

  9. Categories of Motor Efficiency Measures • Motor Efficiency Upgrades • Improve efficiency of motor driving a particular machine or group of machines • Easy implementation, purchase high efficiency motor • System Efficiency Measures • Shifts the focus from individual components and functions to total system performance • Often more effort required for implementation US DOE – Industries of the Future Workshop Series

  10. Steps for System Efficiency Approach • Must characterize the process load requirements • Match driven equipment to load requirements • Control process load in most optimal manner • Considering all cycles of the process load • Properly match the motor and drive to each other as well as the load • Minimize distribution losses US DOE – Industries of the Future Workshop Series

  11. Industrial Motor System Savings Potential Source: US Dept of Energy; “United States Industrial Motor-Driven Systems Market Assessment: Charting a Roadmap to Energy Savings for Industry” US DOE – Industries of the Future Workshop Series

  12. Motor Efficiency and Losses Shaft Power Out 80-95% Electric Power In 5-20% Stray Losses Friction Windage Core Losses Magnetizing Current Rotor Losses I2R Heating Stator Losses I2R Heating US DOE – Industries of the Future Workshop Series

  13. Items Impacting Motor Efficiency • Motor Speed • For fans and pumps, energy usage varies with the cube of speed (e.g. doubling the speed of a cube-law load increases power demand by eightfold, or 23) • Size of Motor • Oversized motors reduce their operating efficiency, cost more, and contribute to reduced power factor • Motor Load • Motors operate at highest efficiency between 60-100 percent of full-rated load • Voltage Variations • Impact the power factor, slip, and heating of the motor US DOE – Industries of the Future Workshop Series

  14. Motor Part-Load Efficiency Curves US DOE – Industries of the Future Workshop Series

  15. Motor Performance and Voltage Variations US DOE – Industries of the Future Workshop Series

  16. Technology – Common System Improvements

  17. Common Areas for Motor Improvement • Energy Efficient Motors • Adjustable Speed Drives • Non-Slip Belts • Replacement versus Rewinding • Reducing Idling Time • Optimized Motor Size • Increase Power Factor US DOE – Industries of the Future Workshop Series

  18. Energy Efficient Motor Benefits • Higher quality construction • More reliable • Longer warranties • Produce less waste heat • Save significant amounts of energy US DOE – Industries of the Future Workshop Series

  19. When replacing a failed motor . . . Energy Efficient Motors • High-efficiency motors can cost up to 20% more than standard motors • Cost effectiveness determined by • Existing motor efficiency • Operating hours • Electricity Cost *USDOE Motor Challenge Fact Sheet: Optimizing Your Motor-Driven System US DOE – Industries of the Future Workshop Series

  20. ES = energy savings, kWh/yr HP = motor horsepower, HP N = number of motors LF = load factor, % h = annual operating hours ηc = existing motor efficiency ηp = proposed motor efficiency Energy Efficient Motor Saving: Simple Calculation US DOE – Industries of the Future Workshop Series

  21. Adjustable Speed Drive Benefits • Matching motor and load to output • Improved power factor • Improved process precision and tool life • Increased production and flexibility • Extended operating range • Load savings over other throttling methods • Pumps • Fans US DOE – Industries of the Future Workshop Series

  22. HP = motor horsepower, hp LFC = current load factor, % LFP = proposed load factor after ASD is installed, % H = annual operating time, hours η = motor efficiency, % ES = energy savings, kWh/yr Adjustable Speed Drives Savings: Simple Calculation US DOE – Industries of the Future Workshop Series

  23. Fan Control Pump Control Adjustable Speed Drives Savings: Sample Data • Proper estimation of energy savings for adjustable speed drives require pump and fan curve plots US DOE – Industries of the Future Workshop Series

  24. Issues with Adjustable Speed Drives • Create harmonics • Harmonics-mitigating equipment now being packaged with ASDs, maintaining power factor improvements • Heat build-up with sustained operation at low speeds (below 30%) • Decrease starting torque • Higher horsepower ASDs can be specified, enabling a higher starting torque or programmable ASD starting features • Potential motor damage when ASDs located far from motor • For Pulse-width, modulated drives, keep cable length to less than 50-100 feet • Can only be retrofit with inverter duty motors US DOE – Industries of the Future Workshop Series

  25. Efficiency of Belt Connection Method • Most common connection between motors and their loads • Efficiency (lowest to highest) V-belts, cogged V-belts, flat belts, and synchronous belts • Synchronous belts have highest efficiency, but are intolerant of shock loads • Cogged V-belts average 2-4% savings over standard V-belts US DOE – Industries of the Future Workshop Series

  26. Replace versus Rewind • Depends on: • Rewind cost v. new motor cost • Rewind efficiency loss and number of rewinds • Motor size and original efficiency • Annual operating hours • Cost of electricity • Each rewind causes 2% efficiency decrease • Usually best to replace non-specialty motors under 15 HP • If rewind cost exceeds 50-65 percent of new energy-efficient motor price… buy a new motor US DOE – Industries of the Future Workshop Series

  27. Reduced Idling Time • Problem: Power draw from motors and equipment not in use for long periods of time • Hydraulic pumps • Lubrication/cutting fluid pumps • Mixers • Idle no-load current may be similar to the full-load current • Solution: manual or automatic control • Manual: turn off power to motor/equipment • Automatic: switch, sensor or timer connected to on/off US DOE – Industries of the Future Workshop Series

  28. Optimized Motor Size • Motor creep – gradual increase in motor hp for a given application  motors oversized for application • Benefits of properly sized motors • Increased power factor • Increased efficiency • Reduced initial cost Motor efficiency is important in selecting a motor, but consideration of the application and proper sizing for that application can save more energy. US DOE – Industries of the Future Workshop Series

  29. Optimized Motor Size: Sample Savings Sample savings by replacing two 100HP motors operating at 60% load and 75% load compared to 60HP motor and 75 HP motor US DOE – Industries of the Future Workshop Series

  30. Improve System Power Factor • Minimize operation of idling or lightly loaded motors • Replace standard motors as they burn out with energy-efficient motors • Operate motor near its rated capacity to realize the benefits of a high power factor design • Install capacitors in your AC circuit to decrease the magnitude of reactive power US DOE – Industries of the Future Workshop Series

  31. Technology – Next Steps

  32. IAC implementation trends and analysis US DOE – Industries of the Future Workshop Series

  33. How to start • Steps in evaluating your system • Best Practices US DOE – Industries of the Future Workshop Series

  34. Steps in Evaluating Motors • Identify the “critical few” from the “trivial many” • Typically, 20% of a plant motor population attribute for 80% of the energy usage • Concentrate first on motors with large horsepower and high duty cycles • Determine if motor sizes are appropriate • Spot Readings • Monitoring • Determine of control strategy is appropriate • Implement MotorMaster 4.0+ Software • Implement high efficiency replacement program • Track repair vs. rewind • Actively manage motor population US DOE – Industries of the Future Workshop Series

  35. Best Practices - MotorMaster 4.0+: Overview • Energy-Efficiency Motor Selection & Management Tool • Available as downloadable software or on-line from DOE-OIT • User-friendly input screens • Large database of motors • By size, efficiency, type, manufacturer, etc. • Flexibility in data entry • Enter in unique operating hours for each motor • Enter utility costs, energy (kWh) and demand (kW) US DOE – Industries of the Future Workshop Series

  36. MotorMaster 4.0+: Capabilities • Management tool • Inventory management • Maintenance logging • Economics • Lifecycle costing • Savings tracking and trending • Energy conservation analysis • Savings evaluation • Energy accounting • Environmental reporting • Decision making • Rewind/replace evaluation • Motor purchase evaluation US DOE – Industries of the Future Workshop Series

  37. MotorMaster 4.0+: For Evaluating New Motor Purchases For New Motors • Enter in Utility Costs • Select Motor • From known motor information • From Catalog • Savings Calculated US DOE – Industries of the Future Workshop Series

  38. MotorMaster 4.0+: For Evaluating Replace vs. Rewind For Rewind Comparison of rewinding vs purchasing a new motor US DOE – Industries of the Future Workshop Series

  39. MotorMaster 4.0+: For Evaluating Replacing Existing Motors For Replacing US DOE – Industries of the Future Workshop Series

  40. In house assessment • Tools available from US DOE Motor Challenge Program • US DOE Industrial Assessment Centers • Energy Resources Center @ UIC • Private energy service companies Assessing your current system • Motor manufacturers US DOE – Industries of the Future Workshop Series

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