Energy Saving in Electric Motor Systems Electric Motors Electric Motor Systems The Electric Motor System E= E e * E m Why Motors Are Important Electric motors consume more than 50% of all electricity consumed in the United States (38.5% in IRAN) Industrial electricity Use Industrial Motor Energy Use by Application Motor Content in IRAN : ( ): Electricity Consumption Comparison US : 2001 IRAN : 1379 Why Energy Saving ! In the US: motors use 23% of all electricity consumed motors use 69% of all industrial electricity consumed Other countries, developed and developing, have similar or even more pronounced motor consumption patterns. For example: In China: motors use 54% of all electricity consumed Why Care About Electric Motors? A small increase in efficiency can realize large savings Why Energy Saving in Motors Considerable Potential Opportunities for Energy Saving in Electric Motors A small increase in efficiency can realize large savings Some opportunities are inexpensive to implement A Motor Can Consume Its Capital Cost in Just 40 Days Continuous Operation Days of Operation Motor Capital Cost / Energy Cost (%) For a 100 hp motor operating for 15 years at $0.05/kWh Purchase Cost = $5,000 Energy Costs = $525,000 Saved Energy Is Pure Profit.. Potential Motor System Savings in US Potential Motor System Savings Based on the US DOE study, implementing viable motor systems savings projects can reduce motor system energy consumption in manufacturing by about 15%. Potential Savings in Pump Systems Potential Savings in Fan Systems Potential Savings in Compressor Systems Potential Motor System Savings Total Electricity Consumption : Motors Electricity Consumption : Potential Electricity Saving : IRAN 28 e9 18 e9 3 e9 US 1085 e9 kWh 680 e9 kWh 85 e9 kWh End User Case Studies 3M Company 3M 1994 . $1,600,000 $ 823,000 1.94 . Bethlehem 15,500 MWh 50 % . $ 1,125,000 $ 620,000 2 . General Motors Pontiac . $ 44,900 $11,200 . Johnson & Johnson Dust Collector 50hp, 25hp 20 hp $50,000 $ 35,000 . Greenville 148,847 kWh . $ 37,190 $ 77,266 6 . Motor efficiency = Motor output / Motor input = 13.8kW (estimated) / 14.9 kW = 0.93, or 93% Pumping Systems: Motor Only The Electric Motor System Pumping Systems: Motor + Pump P suction = 28 psig P discharge = 80 psig Combined pump + motor efficiency = Pump output / Motor input = 10.2 / 14.9 = 0.69, or 69% The Electric Motor System Pumping Systems: Motor + Pump + Valve More than 40 psi drop across the throttle valve Package efficiency = Hydraulic output / Motor input = 2.7 / 14.9 = 0.18, or 18% The Electric Motor System Energy Consumption in Electric Motor Systems E : (kWh) P : (kW) t : (h) : c : (Rls/kWh) C : (Rls) : . . . . 1 2 t, c 3 4 5 6 P 7 8 ( ) P, Power Quality . . : ( 1%) Voltage Unbalance derate ( ) derate ( ) (HVF) Vn : n n : Running Time Management On/Off . . . Energy Saving Motor & Load Matching Electric Motors A/C Induction Motors Induction motors The most common type of electric motors about 90%. Low Cost Robust and Reliable Low Maintenance Simple to Install Easy Availability Why Do We Use Them? A/C Induction Motors Induction Motor Rating as per IEC - Motor Partial Load Factor Efficiency and power factor are a function of motor load Motor Load Efficiency or Power Factor Efficiency Power Factor Motor Partial Load Factor Motor Partial Load Efficiency Reasons for Over Sizing: Extract form DETR Best Practice Guide 1998 Motor Part Loads in the US Office of Energy Efficiency & Renewable Energy US Dept. of Energy Energy Saving Determining Motor Part Load Determining Part Load Input Power Measurement Determining Part Load Line Current Measurement Determining Part Load The Slip method Determining Efficiency On site efficiency Energy Saving More Efficient Transmissions - . - V Energy Saving Energy Efficient Motors Efficiency Motor Efficiency & Losses Iron loss in core - Low loss steel - Thinner laminations Bearing friction & windage loss = 23% - Smaller cooling fan Rotor loss Copper loss = 20% - Optimum slot fill - Larger conductors Stray loss = 7% - Improved slot geometry 50% Breakdown of Loss Components Motor Load (%) Loss (% FL) Iron LossF & W LossStator Cu LossRotor Al LossStray Loss Induction Motor Losses A/C Induction Motors Energy Losses Within a Motor Stator Copper Loss Rotor Conductor Loss Iron Loss Friction & Windage Loss Stray Load Loss Loss Calculations P Fe and P fr,w : from no-load test P stator and P rotor : from R, s and P in P additional : can not be measured directly JEC 37: assumes P additional = 0 IEC : P additional = 0.5%. P in IEC : P additional by measurement or fixed amount depending on motor rating A/C Induction Motors Single-phase Equivalent Circuit Stator Current Rotor Current Load No Load Current Stator Supply Voltage Stray Load Loss Best method of determining P additional : calculate P additional for various load levels as Linearise and correct for measurement errors in function of torque squared as Determining SLL Measurement set-up Efficiency of motors should meet Standards Efficiency standards Europe: IEC , and the new IEC US: IEEE Method B Japan: JEC 37 Difference in efficiency value: up to 3% Why such a difference? in U.S. IEEE Standard Induction Motor Efficiency Energy Efficient Motor Efficiency in EU IEC Efficiency Against Load 25% 96 Load Efficiency % %75%Full Load Energy Efficient Standard 6.5% 3% Characteristics of Energy Efficient Motors Typical Data for 7.5kW, 4 Pole Motor Load Power Factor Standard Energy Efficient Calculation of Energy Saving for EEMotors Calculation of Simple Payback for EEMotors Upgrading one, 1 Horse power motor to a Premium Efficient motor.... Every year will eliminate: 1 Drum of Oil from being burned 520 lbs. of coal from being burned Up to 1,400 lbs. of carbon emissions from being released into the atmosphere That is just one year Motors can last up to 15+ years and.... or.... Energy Saving Replacement vs. Repair Economics of Replacement vs. Repair Depends on many factors... Running hours Load Cost of electricity Cost of new motor Cost of motor repair The Real Cost of Rewinding a Motor It is generally considered that repairing a motor is the low cost option, but even a good rewind will reduce motor efficiency by up to 0.5% Example: 15kW motor with an Efficiency of 90.0% Annual running cost = Motor rewound with an Efficiency of 89.5% Annual running cost = 5,028 Efficiency of Repaired Motors Few empirical studies done -- mostly motors 50 hp and under 77 motors studied, reported efficiency decreased between 0 to 2.5% after repair Average is.5 to 1% efficiency loss Efficiency degradation lower for large hp motors Efficiency loss can be minimized with quality repair Replacement vs. Rewinding Size (kW) Annual Running Hours Repair Replace Energy Saving Adjustable Speed Drive Energy saving Adjustable Speed Drives ASDs give significant savings in energy !!! Adjustable speed drive Why Variable Speed? Motor power is a function of shaft load Load is a function of flow and pressure Reducing flow can reduce power significantly Affinity Laws Flow -- speed Pressure -- speed 2 Power -- speed 3 Experimental results - Drive Variable speed drive, using induction motor and frequency converter Energy saving potential up to 50% in pump drives ventilator drives compressor drives when compared with fixed speed on/off, throttle or bypass system What with efficiency between drives? Motor Torque vs. Load Torque Escalators Motor Torque Loading Weekly Duty Cycle 100% Average Load SundayMondayTuesdayWednesdayThursdayFridaySaturday A Variable Load Adjustable speed drive Adjustable Speed Drives New York State Variable Speed Drive Farm Program kWh in millions Before VSD Saved After kWh in Millions Energy Saving Performance Controller (Soft start) Direct On Line Star Delta Auto Transformer VSD / Inverter Drive Soft Start Current Popular Options Starting of Motors Current Torque Motor Current Speed In 6-10 x In 100% N X Nominal Motor Torque Speed 100% N Excess Starting Torque Excess Starting Current Direct On Line Starting of Motors Initially Relatively Low Cost. Simple Advantages: Starting DOL No Torque Control. High In-Rush Current. Damage To Plant Control Gear. Control Gear Maintenance Cost. Disadvantages: Starting DOL TorqueCurrent Transition Peak up to 20 x In Excess Starting Current Motor Current Speed 100% N 6-10 x In In X Nominal Motor Torque Speed 100% N Delta Torque Star Torque Load Torque Excess Acceleration Torque 0.66 Starting of Motors Star Delta Initially Relatively Low Cost. Simple Reliable In Theory - However In Practice Causes Many Other Problems. Advantages: Starting Star Delta Fixed Torque Reduction. Transition Peak. Damage To Plant Control Gear. Control Gear Maintenance Cost. Disadvantages: Starting Star Delta Torque Current Motor Current Speed 100% N 6-10 x In X Nominal Motor Torque Speed 100% N Motor Torque Load Torque Stepped Acceleration In Starting of Motors Auto Transformer More control than a Star Delta. Proven Technology. Reliable In Theory - However In Practice Causes Many Other Problems. Advantages: Starting Auto Trans Difficult To Design - Often One off. Expensive & Timely To Replace. Large Size. Control Gear Maintenance Cost. Disadvantages: Starting Auto Trans Current Torque Motor Current Speed 100% N 6-10 x In Direct on Line Current Current Limit Start Current Ramp Start X Nominal Motor Torque Speed 100% N Motor Torque Load Torque Powerboss Torque Acceleration Torque 1 1 Unused Starting Current Unused Starting Torque Starting of Motors Soft Start Low Capital Outlay. Complete Control - little on going maintenance. Proven Technology. When a motor cannot be slowed down, a Soft Start is the most effective way to start and stop it. Advantages: Starting Soft Start Adjustable Pedestal Voltage. Adjustable Ramp Time. Adjustable Current Limit. Solid State Electronics - Little Maintenance. Disadvantages: Starting Soft Start Stator & Rotor Ohmic Loss & Stray Load Loss vary with Load Iron Loss & Mechanical Loss (Friction & Windage) nearly are constant to Load. Iron Loss about 20% of total Loss. Energy optimizer by decreasing voltage decrease Iron Loss & therefore increase efficiency. Motor Losses Starting Optimizer in Loads near Full-Load decreasing voltage may cause increasing current & increasing Ohmic Losses! & then increasin total Loss ---> Decreasing Efficiency Just for Loads near no-load Energy Optimizer may decrease total losses by decreasing Iron Loss. Any reputable optimizing soft starter will achieve between 40-50% saving of iron loss. Motor Losses Starting Optimizer Soft Start / Soft Stop. Match Motor and Load Torque. Accurate Control Of Motor Current - Intelligent Reactive Energy Optimisation. Reduction Heat / Noise / Vibration. No adjustment required once fitted - marries with motor. Advantages: Starting Optimizer Energy Saving Preventive Maintenance - - - . - - - -... Energy Saving Lesson Learned Emphasize systems approach Develop portfolio of system-based products and tools Recognize end users and suppliers who are leaders Need for showcases to use as examples that can be duplicated Look for groups (suppliers, utilities, consultants) to promote program A Motor Management Policy Energy Saving...