Table of Contents. Foreword...xiii. Chapter One Introduction, Objectives of the Guide...1

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1 Table of Contents Foreword...xiii Chapter One Introduction, Objectives of the Guide...1 Chapter Two Pumping System Hydraulic Characteristics, System Characteristics Pump Curves Pump Operating Point Typical System Examples Pumping System with Open Reservoir for Pump Intake Parallel Pumps in Common Header Pumping System with Complex Piping System Multiple Branches Pumping System with Complex Piping System Multiple Loops...13 Chapter Three System and Process Introduction, Supply- and Demand-controlled Systems Introduction to Variable Speed Concept Process Requirements...16 Chapter Four Pumps, Classification of Pumps Rotodynamic Pumps Pump Principles and Performance Characteristics Methods of Controlling Rotodynamic Pumps to Meet System Demands...25 iii

2 iv Table of Contents 4.3 Positive Displacement Pumps Rotary Pumps Reciprocating Positive Displacement Pumps Applying Variable Speed to PD Pumps Other Methods of Flow Control for PD Pumps...47 Chapter Five Concepts for Estimating Pumping Energy Costs, Specific Energy Definition Specific Energy Calculation Flow Regulation by Varying Speed of a Rotodynamic Pump Flow Regulated by Throttling System Awareness Notes of Caution Worked Example...53 Chapter Six Motors, Types of Electric Motors Asynchronous Induction Motors Main Types and Operating Principles Motor Efficiency Output Torque Induction Motors Operated at Variable Speed Special Motor Considerations for Motors Run on PWM Waveform Alternative Electrical Designs of Motors Synchronous Motors Direct Current Motors Motor Construction and Cooling Dry Installed Motors Submersible Pump Motors Wet Rotor Motors (Canned Motors) Motor Starting...73 Chapter Seven Variable Frequency Drives, Types of Variable Frequency Drives Variable Frequency Drives for Induction Motors...75

3 Table of Contents v VFD Application Considerations for Positive Displacement Pumps VFD Application Considerations for Rotodynamic Pumps Extended Frequency (Speed) Operation VFD Motor Control Algorithms Power Drive Systems Integrated Motors and Drives Variable Speed Drives for Other AC Motors Variable Speed Drives for DC Motors...84 Chapter Eight Control Principles for Variable Speed Pumping, Control Principles (Methods) for Variable Speed Pumping Main Types of Variable Speed Control Methods Pressure Control Definition P&ID (Process and Instrumentation Diagram) Sensors/Transmitters/Transducers System Considerations for Pressure Control Single Pump Variable Load Multiple Pump Variable Load Flow Control Flow Control Definition Piping and Instrumentation Sensors/Transmitters/Transducers Single Pump Set Flow Rate Level Control Definition P&ID Sensors/Transmitters/Transducers Single-Pump Variable Load Multiple-Pump Variable Load Cyclic-Based Collection Tank Temperature Control Definition P&ID Sensors/Transmitters/Transducers Single-Pump Variable Load Multiple-Pump Variable Load Pumping System Monitoring and Protection Implementation of System Controls...111

4 vi Table of Contents 8.8 Special Consideration for Positive Displacement Pumps PD Pump Control PD Pump Starting Torque PD Pump Operating Considerations Chapter Nine Benefits, Drawbacks, and Operational Issues, Introduction Tangible Benefits to the User Energy Savings Improved Process Control Improving System Reliability Importance of Maintenance Additional Benefits of Pulse Width Modulation Variable Frequency Drives Potential Drawbacks of PWM VFDs Operational Issues General Precautions Resonance and Rotordynamics Power Drive System Integration Operating Pump Motor Systems Above Base Speed Low Base Speed Motors Motor Design Chapter Ten Financial Justification, Life Cycle Cost Life Time Energy Cost Reduction Capital Cost Summary Chapter Eleven Selection Process: New Systems, Selection for Optimum Life Cycle Cost Flowcharts...137

5 Table of Contents vii Chapter Twelve Selection Process: Retrofitting to Existing Equipment, Justification Motor Suitability and Derating Flowchart Retrofitting a Motor-Mounted VFD Chapter Thirteen Case Studies, Introduction Case Study 1: Downsized Pump and Utilization of VFD for Cooling Water Case Study 2: Boiler Feed Pumps Parallel Operation Case Study 3: Water Supply Pump Eliminate Bypass Pressure Control Case Study 4: Booster Pump Set with On/off and Bypass Pressure Control Case Study 5: Water Distribution System Case Study 6: Wastewater Lift Station Using Constant Speed vs. Variable Speed Driven Pumps Case Study 7: Axial Flow Pumps with Eddy Current- Drive Retrofit Case Study 8: Variable Speed Drive on Raw Water Transfer Pump Case Study 9: Installing Variable Frequency Drives on a Potable Water Distribution System in the Caribbean Appendix A Electric Motors, 173 A.1 Energy Efficiency A.2 Efficiency Labeling A.2.1 Europe A.2.2 United States of America A.2.3 Global Regulation A.3 Motor sizing...178

6 viii Table of Contents Appendix B Variable Frequency Drives, 179 B.1 Inverter Designs B.1.2 Current Source Inverter B.1.3 Load-commutated Inverter B.1.4 Matrix Style VFD B.1.5 Switched Reluctance Drive B.2 Rectifier Designs B.2.1 Diode Bridge Rectifier B.2.2 Active Rectifier B.3 Motor Control Strategies B.3.1 Constant Torque V/Hz Control B.3.2 Variable Torque V/Hz Control B.3.3 Load- Optimized V/Hz Control B.3.4 Operating Above the Motor s Rated Frequency B.4 Methods of Controlling Motor Voltage and Dynamic Response B.4.1 Scalar or Voltage/Frequency (U/F, V/Hz) Control B.4.2 Flux Vector Control B.4.3 Closed Loop Control B.5 Factors to be Considered in Selecting Variable Frequency Drives B.5.1 Continuous Motor Current B.5.2 Motor Load Torque Characteristic B.5.3 Incoming Voltage B.5.4 Selecting VFDs for Use with Single-Phase Input Appendix C Legal Obligations, 197 C.1 European Directives C.1.1 The Machinery Directive C.1.2 The EMC Directive C.1.3 The Low-voltage Directive C.1.4 The ATEX Directives C.1.5 The CE Marking Directive C.2 United States Regulations and Standards C.2.1 Federal Regulations C.2.2 Safety Regulations and Standards Appendix D Power Line Harmonics, 203 D.1 Harmonic Current Distortion Limits D.2 Power Line Harmonics and Their Cause...204

7 Table of Contents ix D.3 Harmonic Mitigation Techniques D.3.1 VFD with No Harmonic Mitigation D.3.2 AC line Reactors or DC Chokes D.3.3 Reduced DC Bus Capacitance D.3.4 Passive Harmonic Filters D.3.5 Multipulse Rectifiers and Phase- shifting Transformers D.3.6 Active Rectifiers D.3.7 Active Harmonic Filters D.3.8 Matrix Style VFDs D.4 General Summary Appendix E Effects of Pump Speed and Impeller Diameter on Magnetically Driven Pumps, 221 E.1 Introduction E.2 Changes of Pump Speed E.3 Change of Impeller Diameter Appendix F Non-VFD Drives, 225 F.1 Overview of Variable Speed Technologies F.2 Eddy Current Drives Appendix G Instruments, 231 G.1 Instrumentation Fundamentals G.1.1 Definitions G.1.2 Selection Considerations G.1.3 Pressure G.1.4 Temperature G.1.5 Level G.1.6 Flow Appendix H Definitions, 237 H.1 Glossary H.2 Nomenclature H.3 Abbreviations of Terms H.4 P&ID Terms...254

8 x Table of Contents Appendix I Bibliography, 257 Appendix J Index, 261 List of Figures 1.1 Share of motor electricity consumption Equation for pipeline flow Equation for pumped system Static head System curve Closed loop system Friction head versus flow rate Pressurized tank System curve Rotodynamic pump Positive displacement pump Rotodynamic pump and system curves PD pump and system curves Rotodynamic pump and minimum- maximum system curves Typical curve for parallel pumps in common header Typical branch system with a single pump supplying three circuits, and each circuit has a separate destination A looped system with a single pump and supplying three circuits in a closed loop Classification of pumps Example of pump performance curves Example of speed variation affecting rotodynamic pump performance Example of impeller diameter reduction affecting rotodynamic pump performance Overplot of NPSHR and NPSHA Illustration of wasted head by control method...24

9 Table of Contents xi 4.7 Reducing the speed of the pump reduces both the pump s pressure and flow, which minimizes losses in the system Example of the effect of pump speed change in a system with low static head Example of the effect of pump speed change in a system with high static head Selection of operating point to the right of BEP for static head system Control of pump flow by changing the system resistance using a throttle valve Bypass control for a constant speed pump in a chilled water system When the bypass s resistance to flow is less than the load s resistance to flow, the operating point moves to the right on the pump curve Typical curves for pumps in parallel When additional pumps are added in parallel, the flow in each individual pump decreases Typical curves for pumps in series, with a system curve Slip flow Volumetric efficiency Typical power curves Output characteristic of a single-cylinder pump Output characteristic of a two- cylinder pump Flow characteristic of a three- cylinder pump Flow rate versus speed for a plunger pump Power versus speed for a plunger pump Efficiency versus speed for a plunger pump System curves for Figure Specific energy for three systems Valve throttling losses Specific energy curves High static head examples Low static head examples High static head specific energy Low static head specific energy...55

10 xii Table of Contents 6.1 Classification of electric motors Squirrel-cage induction motor cross section Induced magnetic field in squirrel cage rotor bars Motor efficiency versus speed (nominal 95% efficient motor) Development of torque for permanent magnet motors Simple schematic of switched reluctance motor Cross- sectional drawing of a synchronous reluctance motor Induction motor DOL starting characteristics Types of variable frequency drives Power ranges and application fields for electrical VFDs Basic PWM VFD Simplified PWM VFD output Speed/torque curves for positive displacement and rotodynamic pumps Speed/torque curves for VFDs set up for constant torque Speed/torque curves for VFDs set up for variable torque Illustrations of integrated motor and VFD Proportional integral and derivative control Unstable controller (oscillation) Stable controller Typical pressure control P&ID Typical pressure transmitters Pressure control system Single pump variable speed constant pressure Multiple pump skid for parallel operation Multipump variable speed constant pressure control Multiple pump single VFD and DOL starters Multiple pumps with VFD for each pump Staging example based on specific energy curves Flow control P&ID Typical flow transmitter used Control on constant flow P&ID differential pressure flow control Control by pump power algorithm...101

11 Table of Contents xiii 8.18 Continuous level control P&ID Typical level transmitter used Steam boiler feed application Lift station pump control application Continuous operation and cyclic operation to maximize specific energy P&ID temperature control system Typical temperature transmitters Temperature control downstream of load Differential temperature control Typical vibration signature of discharge head/motor structure Amplification chart Campbell diagram a High static head operation with flow frequency bins b High static head specific energy curves a Low static head operation with flow frequency bins b Low static head specific energy curves Flowchart to assess the suitability of using a VSD in a rotodynamic pump system Flowchart to assess the suitability of using a VSD in a positive displacement pump system Flowchart for selection of the correct drive and financial justification Flowchart to assess the suitability of retrofitting a VSD to an existing pump system Initial installation and control diagram Pump curve full speed operation Pump and system curve variable speed operation Initial installation and control diagram Motor current strip chart Operating condition before modification Operating conditions after modification Initial installation and control diagram Operating condition before modification Modified installation and control diagram...152

12 xiv Table of Contents Average operating conditions Variable speed operating range Original installation and control diagram Modified installation and control diagram New pumps with integrated VFDs Original installation and control diagram Original pump system operation Diurnal flow rate demand curve Modified installation and control diagram Comparison of power consumption Average daily diurnal flow rate Pumping system and control with constant speed drives Pumping system and controls with variable speed drives Pumping system energy consumption chart Pumping system specific energy comparison Variable speed new pump and system curves Original installation and control diagram Variable speed pump curve Pump system layout Pump installation, piping, and pressure- reducing valve Histogram of total system flow during two- pump operation Variable speed performance compared with system head Pumping system and controls with variable speed drives A.1 Typical life cycle cost of an electric motor A.2 Efficiency comparison between premium and standard efficiency AC induction motors B.1 Basic PWM VFD B.2 Basic CSI main circuit B.3 Basic LCI main circuit B.4 Matrix style VFD main circuit B.5 VFD for a switched reluctance motor B.6 VFD with a diode bridge rectifier B.7 VFD with diode bridge rectifier, braking resistor and braking chopper transistor...184

13 Table of Contents xv B.8 VFD with an active rectifier and input filter B.9 Power diagram of the inverter section of a basic variable VFD B.10 A constant ratio of voltage to frequency supplied to the motor B.11 A constant V/Hz ratio from the drive B.12 The low- speed torque requirements of variable torque and constant torque loads B.13 A variable torque V/Hz ratio matches the magnetizing current in the motor to the requirements of a typical variable torque load B.14 By monitoring the load on the motor s shaft, a VFD can automatically adjust its output voltage B.15 VFD output voltage B.16 Motor operation above nameplate frequency relationship B.17 Torque requirements B.18 Power availability at the motor s shaft as the operating frequency extends above the rated value C.1 EMC aspects of a power drive system D.1 Three- phase input rectifier section for a PWM VFD D V AC sinusoidal voltage supplied to the VFD s input rectifier D.3 Rectified AC voltage into DC from a single-phase power source..205 D.4 The DC voltage pulses for a VFD connected to a three- phase power source D.5 The DC bus capacitors filter the DC bus voltage (in red) and store it for use by VFD s inverter section D.6 While a resistive load (blue) draws a peak current of about 30 A, the nonlinear load (red) of the same size draws a peak current of over 60 A D.7 Single- phase undistorted AC current (in blue) and distorted AC current (in red) D.8 Phase L1 current for a three- phase non linear load. The two peaks are for current L1 to L2 and L1 to L3. The area with no peak is when L2 is conducting L D.9 Current distortion can distort the voltage in the power source, as shown by the flattening of the voltage near its peak value D.10 A VFD with no harmonic mitigation D.11 A VFD with input AC line reactor...209

14 xvi Table of Contents D.12 A VFD with input DC choke D.13 Some VFDs use small DC bus capacitors to reduce their THiD D.14 A passive harmonic filter uses parallel capacitors to store energy that is used to provide peak current that the VFD requires D.15 The contactors just above the capacitors are used to disconnect the capacitors when the system is lightly loaded D.16 A 12 pulse rectifier with phase- shifting transformer D.17 An 18 pulse rectifier with phase- shifting transformer D.18 VFD with active rectifier for harmonic mitigation D.19 An active harmonic filter monitors a section of the AC power source and actively responds to correct power quality issues D.20 A matrix style VFD uses a network of IGBT s to directly switch current from the building s power to the driven motor F.1 Block diagram of an eddy current drive List of Tables 4.1 Control methods overview a High static head, metric units b High static head, US customary units a Low static head, metric units b Low static head, US customary units No-load (synchronous) speeds for typical motors with different pole numbers and supply frequencies Insulation and temperature rise classes Typical motor losses Motor frame output relationship for two typical motors Performance compared to an inverter- fed induction motor Comparison of motor efficiencies Summary of drive applicability Main PID tuning methods Configurations and control principles for multiple pump operation Control methods for constant flow applications using a single pump Common faults and causes

15 Table of Contents xvii 8.5 PD pump variables to be considered in speed control Motor designs Influence of VSD on LCC a High static head life cycle energy cost results, metric units b High static head life cycle energy cost results, US customary units a Low static head life cycle energy cost results, metric units b Low static head life cycle energy cost results, US customary units Return on investment (ROI) calculation ROI calculation ROI calculation ROI calculation ROI calculation ROI calculation Capacity variation Drive efficiency comparison Cost of energy comparison Variable speed energy savings per pump ROI calculation ROI calculation ROI calculation A.1 EU MEPS implementation A.2 Efficiency classes A.3 Old versus new threshold B.1 Summary of inverter designs and characteristics D.1 Summary of harmonic mitigation methods for VFDs F.1 Other types of variable speed drives

ELECTRICAL POWER and POWER ELECTRONICS

Introduction to ELECTRICAL POWER and POWER ELECTRONICS MUKUND R PATEL (cj* CRC Press Taylor & Francis Group Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Croup, an informa