AshraeMoncton2009

,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,Variable Frequency Drives & Motors in the HVAC Industry,ASHRAE,NB PEI Chapter,May 12, 2009,1,HVAC Variable Frequency Drives,Pumps Fans Towers,2,3,Control HP Save Energy,Flow,Speed,HP,Speed,3,At 50% Speed, HP = 12.5%,Centrifugal Loads,Used to be the main topic,4,Affinity Laws,Flow vs Speed,Q,1,/Q,2,= S,1,/S,2,Head vs Speed,H,1,/H,2,= S,1,2,/S,2,2,HP vs Speed,bhp,1,/bhp,2,= S,1,3,/S,2,3,5,Typical HVAC VFD Applications,Fans,AHU (Supply Air Fans),Return Air,Exhaust,Cooling Towers,Evaporative Condensers,Pumps,Chilled Water,Condenser,6,7,8,Energy Savings,Head,Head,Power,Power,Throttling (riding the curve),VFD (varying the speed),Speed 1,Speed 2,9,Variable Frequency Drives,Over 25 years of HVAC applications,Fundamental principal remains unchanged,Convert line voltage & frequency to controllable values and apply to induction motors,For a 4 pole motor:,60Hz = 1800 rpm,30Hz = 900 rpm,The preferred choice to achieve variable flow control,10,Variable Frequency Drives,Numerous advancements over the 25 yrs,Power devices evolved:,Thyristor (SCR) GTO Bipolar Transistor to present day IGBT devices,IGBT (Insulated Gate Bipolar Transistor):,Faster Switching / Higher performance,Lower losses / Higher efficiency,Smaller packaging,Robust / Increased,reliability,11,Variable Frequency Drives,Numerous advancements over the 25 yrs,Microprocessor power:,Better control and accuracy,Enhanced firmware,High speed current limit “Tripless”,Regen Avoidance,Built-in PLC Function,PID control loop,Network communications:,BACnet MSTP, BACnet IP, FLN, N2, LonWorks,Modbus RTU, Modbus TCP/IP,Today VFDs are rated for 100kA interrupt capacity,12,Keypad,Store Multiple Parameter Sets,Upload / Download Parameters,Download Parameters without powering up the VFD,13,High Speed USB port to capture oscilloscope type data traces,14,15,Input Line,Filter Capacitor,Inverter,Rectifier,AC Motor,Typical PWM VFD,575/3/60,AC to DC,DC to AC,0 - 575V,0 - 60Hz,Speed,Hz,Torque,V,/,Hz,DC Bus,PWM Output,16,Motors,Manufactured to Nema MG1 standard,Part 30,General Purpose not generally associated with VFD applications,Insulation rated for 1000V / 2,m,sec rise time (majority of quality motors rated for withstand voltage of 1200V to 1400V),Note that specs such as Class B or F relate to temperature classes not voltage withstand rating. Similarly efficiency ratings also do not relate to voltage withstand ratings.,17,Motors,Manufactured to Nema MG1 standard,Part 31,Definite Purpose Inverter Duty,Insulation rated for 1600V / 0.1,m,sec rise time,Note that specs such as Class B or F relate to temperature classes not voltage withstand rating. Similarly efficiency ratings also do not relate to voltage withstand ratings.,18,Motors,Manufactured to Nema MG1 standard,Part 31,Definite Purpose Inverter Duty,Insulation rated for 1600V / 0.1,m,sec rise time,Newer motor designs rated for 2000V,Speed Turndown range,CT 10:1,VT 100:1,5 Year Warranty,19,Motors,Comments and Recommendations,The voltage withstand rating relates to the voltage waveform applied to the motor windings,When connected to the line a normal sine wave has a peak voltage of approx 800V,PWM output with voltage reflection due to fast rise time (0.1,m,sec) and long cable can approach two times the peak voltage (1600V).,Recommend using a Nema MG1 Part 31 motor for new installations,For retrofit installations use an output LRC dv/dt filter,Some installations with short cables can use a load reactor.,20,Component VFD vs Packaged System,Stand Alone Component VFD,VFD mounted and individually connected to external components (in their own enclosures) such as:,Disconnects or Circuit Breakers,Fuses,Reactors and/or filters,Bypass components,Packaged System,VFD and components mounted and wired in a Nema 1 wall or floor mount enclosure,21,Component VFD vs Packaged System,A Packaged System provides the following benefits:,More cost effective vs Field mounting and interconnecting,Less space required,Avoids finger pointing re warranty issues,Reduces material management on site,22,System Components,Fused Disconnect,Line Reactor or Harmonic Filter,VFD,Load Reactor or LRC filter,Bypass,O/L,23,Many devices are defined as,non-linear,and “draw” current from the line in such a manner as to induce current harmonics. Examples are:,Adjustable Speed Drives (AC & DC),UPS,Switch-mode power supplies (computers),Electronic ballasts,Phase converters,Harmonics,24,What Are Harmonics,Basic power source is 575/3/60,Base or fundamental frequency is 60Hz - Sinusoidal,We will see that VFD line current is a distorted waveform,A repeating, distorted waveform can be expressed as the,Fundamental,+,multiples of the fundamental,25,Most common loads do,not,cause harmonics e.g.,Incandescent light bulbs,Baseboard heaters,Motors,These are known as,Linear Loads,The current they draw “follows” the voltage,Loads,Without,Harmonics,26,These are known as,Non-Linear,Loads,The current they draw does,not,“follow” the voltage,Loads,With,Harmonics,27,Harmonics,Voltage,Current,Linear,Load,Fund. Current,Non-Linear,Load,Fund. Current + Harmonics,28,Harmonics,Non-Linear Load,High,Harmonic Content,Non-Linear Load,Reduced,Harmonic Content,Voltage,Current,29,What are Harmonics?,Fundamental (60Hz),2,nd,Harmonic (120Hz),3rd Harmonic (180Hz),30,Fundamental,7th,Harmonic,5th,Harmonic,Harmonics,Fundamental + 5th Harmonic + 7th Harmonic,Note: Lowest harmonic in 6 pulse VFDs is the 5th,31,Effects of Harmonics,Previous slides referred to Current Distortion,Current Distortion results in Voltage Distortion,Potential for overheating of Transformers, Motors,Harmonic resonance,High neutral currents (1 ph - 3rd harm.),32,IEEE 519,Originally introduced in 1981 to place limits of Voltage Distortion on the power utility at a point of common coupling between users at the Utility level.,The 1992 revision added limits of Current Distortion relative to the system in which non-linear loads are utilized.,33,6 & 12 Pulse Configuration,6 Pulse,12 Pulse,+,+,-,-,34,IEEE 519,A simplified summary of the 1992 revision can be expressed as:,A “small” non-linear load installed in a large or stiff system will not result in excessive harmonic distortion.,As the ratio of non-linear loads vs system capacity increases, mitigation of harmonic levels may be necessary.,35,Table 10.3, p78,Current Distortion Limits for General Distribution Systems,(120 V Through 69,000 V),Maximum Harmonic Current Distortion in Percent of I,L,Individual Harmonic Order (Odd Harmonics),I,SC,/I,L,11,11,h17,17,h23,23,h35,35,h,TDD,20*,4.0,2.0,1.5,0.6,0.3,5.0,2050,7.0,3.5,2.5,1.0,0.5,8.0,50100,10.0,4.5,4.0,1.5,0.7,12.0,1001000,15.0,7.0,6.0,2.5,1.4,20.0,Where:,I,SC,= maximum short-circuit current at PCC.,I,L,= maximum,demand load,Notes:,1.,Even harmonics are limited to 25% of the odd harmonic limits above.,2.,* All power generation equipment is limited to these values of current,distortion, regardless of actual I,SC,/I,L,.,IEEE 519 - 1992,current (fundamental frequency component) at PCC.,Current distortions that result in a dc offset, e.g., half-wave converters, are not allowed.,36,IEEE 519 PCC,Xfmr 1,Xfmr 2,M,M,M,M,VFD,xx,MVA 69kV / 13.8kV,xx,kVA 13.8kV / 480V,PCC-1,PCC-2,“X”,37,IEEE 519 - PCC,From the previous slide:,The intent of IEEE 519 is not to “define” the PCC as point “X” but rather as points PCC 1 or 2 depending on the Utility metering point. (TDD applied here),If Xfmr 1 has a large MVA value the I,SC,will be large as well leading to a greater I,SC,/I,L,value thus a higher allowable TDD.,38,IEEE 519 - PCC,From the previous slide:,The practice suggested is to reduce the harmonic distortion at point “X” but measure the results at the PCC which is the intent of IEEE 519,Specifying that TDD be met at point “X” can lead to expensive solutions and may not be possible.,39,IEEE 519 - PCC,From the previous slide:,If calculated levels of both Current and Voltage distortion are required at the quotation stage the following must be made available:,A single line diagram,Transformer details to calculate Isc,Load details to calculate I,L,A specified PCC,40,Harmonic Solutions,Reduce Harmonic Levels by:,Adding Line Reactors,12 , 18 .Pulse Configuration,Add Tuned Filter Traps,Add Passive Broadband Filters,Add Active Filters,Add Active Front End,If the IEEE 519 levels at the PCC cannot be met, then harmonic mitigation must be employed.,41,Harmonic Solutions,A 6 pulse VFD without any filtering will typically have a current distortion level of approximately 75%,Adding line reactors will reduce this to 35-40% at a low cost,Mid level filtering or 12 pulse systems can achieve levels of 9-15% at increased cost,The various solutions will reduce current distortion values in varying degrees,42,Harmonic Solutions,High level filtering or 18+ pulse systems can reduce the current distortion level down to approximately 5% at a further increase in cost,43,Summary,The solutions have limitations,Tolerance of Voltage unbalance,Leading power factors at light load,Compare efficiency,Compare size,44,45,Note physical size of Harmonic Filters relative to Drive Panels beside them,46,Bypass Packagewith Input andOutputReactors,47,Summary,There are various solutions,Specify performance not the method,48,