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Presented by: Johnny Douglass Washington State University Extension Energy Program Date: February 15, 2005 Sponsored by: Los Angeles Department of Water and Power, and U.S. DOE Industrial Technologies Program. Information Resources Through WSU Energy Program.
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Presented by: Johnny Douglass Washington State University Extension Energy Program Date: February 15, 2005 Sponsored by: Los Angeles Department of Water and Power, and U.S. DOE Industrial Technologies Program
Information Resources Through WSU Energy Program • U.S. DOE Industrial Technologies Program (ITP) BestPractices 1-877-337-3463 www.oit.doe.gov/bestpractices/motors
USDOE ITP Best Practices Websites: Best Practices www.oit.doe.gov/bestpractices Motorswww.oit.doe.gov/bestpractices/motors Information Center: 1-877-EERE-INF 1-877-337-3463
Big Picture Perspectives: Industrial Motor Systems • Industrial motor systems: • Are the single largest electrical end use category in the American economy • Account for 25% of U.S. electrical sales.
What is the BestPractices Program? • Supports the DOE "Industries of the Future", the eight most energy-intensive industries in the U.S. • Offers tools and techniques to improve plant energy efficiency, enhance environmental performance, and increase productivity • Systems included are motor, steam, compressed air, and process heat.
What does BestPractices do? • Brings emerging technologies into use: • Showcase demonstrations • Technology deployment. • Provides assistance to IOF customers: • Plant-wide energy assessments • Information clearinghouse • Software tools and training.
Independent of energy factors, motor systems are vital to overall plant production and safety • Material handling and transport • Fluid movement • General utility support • Building and process temperature, humidity, contaminant, etc. control. For example, motor systems provide:
Component and system approaches to energy and reliability improvement contrasted Component optimization involves segregating components and analyzing in isolation System optimization involves looking at how the whole group functions together and how changing one can help another
Given their energy, productivity, and reliability significance, motor-driven systems are clearly an asset that merits management attention
A motor SYSTEM is the entire energy delivery process, from electric feed to finished product Utility feed Ultimate goal Trans- former ? Breaker/ starter ASD (maybe) Driven Load Motor Mechanical Work
Which systems merit the most attention?Some likely candidates: • "Bad actor" systems • Production-critical systems • Systems with the greatest potential savings But which ones are those?
The Pareto Principle or "the vital few and trivial many" J. M. Juran, who first used the term "Pareto Principle" also coined a more descriptive phrase: "The VITAL FEW and the trivial many" (Relatively few are responsible for relatively much) Input Output 80% 20% 80% 20%
Prescreening to narrow the field of focus - i.e., to select the VITAL FEW for further review All plant motor systems Big loads that run a lot Big centrifugal loads that run a lot Filter 1 Filter 2 Symptom or experienced-based segregation Seldom used, small loads Large non- centrifugal loads * * Policies and Procedures Bin Moderate Priority Highest Priority * Productivity/reliability-critical systems sent to higher priority levels
Policies andProcedures Bin • Devise Standard Policies and Procedures (P/P) for small and seldom used motors, e.g.: • Schedule preventive maintenance like cleaning and lubrication • Scrap all failed motors under 50 HP • Use NEMA Premium replacement motors. • Even small and seldom used motors advance to higher priority if they are production or reliability critical.
ModeratePriority • Includes larger or higher annual utilization motors • Track inventory of all moderate priority motors • Implement preventive maintenance • Base repair/replace decisions on MotorMaster analysis • Even seldom used motors advanced to highest priority if they are productivity or reliability critical.
HighestPriority • 200 HP and above • Large centrifugal loads • Production critical process (reliability issue) • “Bad Actor” systems • Over 2000 hours per year utilization • Implement predictive and preventive maintenance.
Elements of a good motor systems management plan • Includes a preventive and predictive maintenance program • Applies EASA and ITP guidelines for selecting repair shops and ensuring quality repair • Implements a replacement and new motor purchase plan to ensure minimum cost over the life of each motor by considering: • Initial cost • Matching performance to load requirements • Operating efficiency (Usually NEMA Premium is the best choice).
Distribution of industrial motor-system energy Just over 1/3 of the motor population accounts for almost 2/3 of the energy Other 4.3% Pumps 24.8% Material processing 22.5% Material handling 12.2% Fans 13.7% Refrigeration 6.7% Compressed Air 15.8%
A small fraction of the motor population is responsible for most of the energy consumption 10% Population uses 80% energy Energy Population Note the descending order (left to right)
Percent Electric Energy Driving Motors 100 90 80 70 60 Percentage 50 40 30 20 10 0 Mining All Industrial Metal Production Metals Fabrication Process Industries Oil and Gas Extraction Agricultural Production Mon-metals Fabrication Water, Sewerage, Irrigation
Typical Motor System Losses Useful Work Load modulation devices 0 to >50% Coupling device losses <1 to >10% for large speed reduction Controller losses <1 to ~5% for ASD Driven load losses 30 to 50% for pumps and fans Electrical distribution system losses <1 to 5% Motor losses 3.5 to >10%
Probably the most common basis for purchasing decision-making is first cost Purchase + installation cost 30 A through C represent three alternative choices 25 20 15 Cost, K$ 10 5 0 A B C Option
In the life cycle perspective,initial costs become minor factors A B C 500 450 400 350 Solid color is range of uncertainty 300 250 Cost, K$ 200 150 100 50 0 First cost Energy NPV Maint. NPV
Purchase/installation, energy, and maintenance life cycle cost comparison 800 $491k - 673k 700 600 $433k - 524k $443k - 507k 500 400 Cost, K$ 300 200 100 0 A B C
Some challenges with life cycle costing • Actual life estimation • Risk • Reliability
Relative importance of assumptions and general risk can be gained from a simple sensitivity study NPV vs. discount rate analysis for motor replacement 3000 10-yr life 2000 IRR = 8.5% 9-yr life 1000 Net present value, $ 8-yr life 0 -1000 -2000 3 4 5 6 7 8 9 10 Discount rate, %
Alternatives and supplements to life cycle cost analysis • Probabilistic analysis of reliability & risk (commercial software is available) • Engineering judgment • Weighted/graded evaluation • Sole-source contracting (initial selection would involve overall cost/reliability considerations) • Outsourcing - shed some of the decision-making responsibility.
Contingency planning - making the change when a failure occurs • The alternatives evaluation picture changes dramatically when failures occur. • Changes that couldn't be justified when the system was functional may very well be after failure. • The alternative may actually be less costly than simple repair/replacement of the existing component.
Forget First Cost! • 100 HP TEFC EPACT motor costs ~ $4,543 • It costs $27,430 to operate per year! • @ $.05/kWh & $8/kW, 5000 hrs, 100% load
Before Screening • For any motor-driven piece of equipment, ask yourself “Can it be turned off?” • It is an amazingly common action, particularly in systems with multiple or parallel pieces of equipment. • Savings are guaranteed to be 100%.
Induction Motor DesignNEMA Designation Letters • Design B: Most common design. NEMA specifies minimum locked rotor, breakdown, and pull-up torque and maximum locked rotor current.
Induction Motor DesignNEMA Designation Letters • Design A:Less common than B. Identical to B, except locked rotor current has no upper limit. • In applications where Design B works and starting current is not a concern, search for the most efficient motor among both Designs A and B. • Good applications include those with a soft starter or VFD and anywhere that the distribution system is stiff enough to handle a little higher starting current without unacceptable voltage sag. See MotorMaster+ for exact locked rotor current of individual motors.
Induction Motor DesignNEMA Designation Letters • Design C:For loads with high starting and accelerating torque requirements. Higher minimums for locked rotor and pull-up torques than Designs A and B. Same limits on slip and locked rotor current.
Induction Motor DesignNEMA Designation Letters • Design D:Designed for varying torque loads like punch presses and oil well pumps. Typically used with a heavy flywheel to carry through peak torque demand. Slip higher than 5%, sometimes much higher. Very high locked rotor torque. Efficiency low.
Induction Motor DesignNEMA Designation Letters • Accelerating torque curves vary considerably for different motor designs. • In most cases, Designs A or B will provide sufficient torque. They also tend to have the highest efficiencies. A or B
Frame Type/Size Voltage Rated Horsepower Amps, Rated Load Time Rating, i.e. Duty Maximum ambient Temperature RPM at Rated Load Insulation Class Design Letter Service Factor Frequency Number of Phases Locked Rotor Code, MG1 Part 10.37 Efficiency, Rated Load Other Optional Information Nameplate Information
S.F. 1.15 Service Factor • Motors can be overloaded to somewhat exceed their horsepower rating. • Service factor represents allowable overload for which the motor can be run continuously at nameplate voltage and frequency. • Motors’ power factor, efficiency, and life expectancy are reduced by operation in service factor so specify motors sufficiently large that service factor operation will occur infrequently.
Efficiency Basics: What makes a motor energy efficient or NEMA Premium? ? ? ? ? ? ? ? ?
How is efficiency defined? NEMA Premium and Energy Efficient Motors: Are they really “plug ‘n’ play”? How much more efficient are they? Are they worth the price? How is their performance, other than energy efficiency? Questions About Efficiency
What is efficiency? • Efficiency = Output / Input • Efficiency = (Input - Losses) / Input • Efficiency = Output / (Output + Losses) • They’re all mathematically equivalent.
How is efficiency determined? • The Institute of Electrical and Electronics Engineers (IEEE) provides testing standards for the determination of motor efficiency in IEEE Std 112-1996 “IEEE Standard Test Procedures for Polyphase Induction Motors and Generators”. • IEEE also sets minimum efficiency requirements in its IEEE Std 841-2000 “IEEE Standard for Petroleum and Chemical Industry--Severe Duty Totally Enclosed Fan-Cooled (TEFC) Squirrel Cage Induction Motors– Up to and Including 370 kW (500 hp)”.
Who defines energy efficient? Industry: National Electric Manufacturers Assn. • Sets labeling standard for “Energy Efficient” and “NEMA Premium™” motors from 1 to 500 HP and medium voltage motors from 250 to 500 HP. Government: EPACT • Sets minimum efficiency standard for certain new 3-phase motors from 1 to 200 HP. Levels identical to NEMA’s “Energy Efficient” classification.
NEMA Definitions • “Energy Efficient” • This covers 3-phase induction motors with efficiencies equal to or exceeding that in table 12-10 of NEMA’s MG 1 standard. It pertains to low voltage (<600V) motors from 2-poles to 8-poles and 1-500 HP. • “NEMA Premium™ Efficient” • This covers 3-phase induction motors from 2-poles to 6-poles. It pertains to low voltage motors from 1-500 HP and medium voltage (>600 & <5000V). NEMA Premium standard ranges from around 1% more efficient than “Energy Efficient” on 200 HP motors to about 3.5% more efficient on 1 HP motors. See http://www.nema.org/premiummotors/
Are NEMA Premium™ efficient motors... • More or less reliable? • Not necessarily correlated. But some manufacturers offer a premium line that may combine better efficiency with other aspects. • More fragile? • No. Nothing in their design is inherently more or less tough. • Bigger? • No. The same standard frame sizes are available.
What’s in a NEMA Premium™ motor? All the same things; just more and better materials and closer tolerances to help the motor meet NEMA’s premium standard, including: • Larger wire gage – Lower stator winding loss • Longer rotor and stator – Lower core loss • Lower rotor bar resistance – Lower rotor loss • Smaller fan – Lower windage loss • Optimized air gap size – Lower stray load loss • Better steel with thinner laminations -- Lower core loss • Optimum bearing seal/shield – Lower friction loss.
External Factors Affecting Efficiency • Efficiency is never constant. External factors can reduce efficiency and require derating. Beginning with the worst, these include: • Voltage unbalance • Voltage deviation • Voltage harmonics. More on this later
Allowable starts per hour and minimum off-time between starts • 10 hp/1800 RPM 12.5 (46 sec) • 50 hp/1800 RPM 6.8 (72 sec) • 200 hp/1800 RPM 4.0 (300 sec) • Source: NEMA Standard MG 10