Introduction to Pekik Argo Dahono Electrical Energy Conversion Research Laboratory Institute of Technology Bandung Why Electric Drives Electric drives are available in any power. They cover a wide range of torque and speed. Adaptable to almost any operating conditions. Electric drives are operable instantaneously. High efficiency. Easily controllable. Can be operated in all four quadrants. Can be built in a variety of designs. 2 1
Limitations of Electric Drives The dependence on a continuous power supply causes problems with vehicle propulsion. Due to the magnetic saturation, electric motors are likely to have a lower power-toweight ratio than high pressure hydraulic drives. 3 Why we need variable speed drives Some industrial process need variable speed drives (robots, machine tools, conveyors, etc.) Some industrial machines will be more efficient if driven by a variable speed drive (pumps, blowers, fans, etc.) Vehicle propulsion system. 4 2
Energy flow and typical losses 5 Energy Team 6 3
Energy Team 7 Pumping System Variable flow variable-pressure Constant-flow variable-pressure Variable-flow constant-pressure 8 4
1 2 Pump Characteristics Pump Power (kw) = k Flow( m Pump Power (kw) = k Q H Pump Energy (kwh) = k Q H t E E = k ( Q H Q H ) Pump Power Speed 1 1 3 2 2 t 3 / h) head( m) 2 FLOW1 RPM1 PRESSURE1 RPM1 2 FLOW2 RPM2 PRESSURE2 RPM2 9 Pumping System with Valve Control FLOW REFERENCE MOTORIZED VALVE SET-POINT CONTROLLER STARTER MOTOR SENSOR PUMP 10 5
Pumping System with VSD FLOW REFERENCE SET-POINT CONTROLLER MOTOR SENSOR PUMP CONTROLLER 11 Variable-flow variable-pressure Pumping System Total Head (FT) 240 200 160 120 80 40 30 40 50 60 Valve Losses Throttled System Curve Unthrottled System Curve 70 75 Throttled Operating Point 78 80 100% SPEED 84% Speed operating Point Pump Output = Power Head (Ft.) x Flow (GPM) x Specific Gravity 3960 0 0 200 400 600 800 1000 1200 1400 1600 1800 Flow (GPM) 12 6
Energy input for variable-flow variable-pressure pump 80 70 VALVE OPERATION WITH STANDARD EFFICIENTMOTOR 60 INPUT KW 50 40 30 ADJUSTABLE SPEED OPERATION WITH ENERGY EFFICIENT MOTOR 20 10 0 500 700 900 1100 1300 1500 1700 FLOW (GPM) 13 Constant-flow variable-pressure TOTAL HEAD (FT.) 240 220 200 180 160 140 120 100 80 60 40 20 30 40 50 60 VALVE LOSSES CONSTANT FLOW CONSTANT SPEED THROTTLED OPERATING POINT 70 75 78 80 REDUCED SPEED OPERATING POINT 100% SPEED PUMP POWER OUTPUT = HEAD x FLOW x SPECIFIC GRAVITY 3960 0 200 400 600 800 1000 1200 1400 1600 1800 FLOW (GPM) 14 7
Constant-flow variable-pressure 70 VALVE OPERATION WITH STANDARD EFFICIENT MOTOR 60 INPUT KW 50 40 30 ADJUSTABLE SPEED OPERATION WITH ENERGY EFFICIENT MOTOR 20 10 0 100 120 140 160 180 200 220 HEAD (FT.) 15 Variable-flow constant-pressure STARTER SENSOR MAIN VALVES MOTOR PUMP MOTORIZED VALVE SET-POINT CONTROLLER CONSTANT PRESSURE REFERENCE 16 8
Variable-flow constant-pressure CONSTANT PRESSURE REFERENCE SET-POINT CONTROLLER MAIN VALVES MOTOR SENSOR PUMP CONTROLLER 17 Variable-flow constant-pressure TOTAL HEAD (FT.) 240 220 200 180 160 140 120 100 80 60 40 20 0 30 CONSTANT PRESSURE CONTROL LINE 40 50 60 MAIN SYSTEM CURVE #2 MAIN SYSTEM CURVE #1 BYPASS CLOSED SYSTEM VALVES OPEN MAIN FLOW MAIN FLOW 200 400 600 800 1000 1200 1400 1600 1800 FLOW (GPM) 70 75 78 CLOSING SYSTEM VALVES OPENING BYPASS VALVE SYSTEM CURVE BYPASS PARTIALLY OPEN BYPASS FLOW BYPASS FLOW 80 TOTAL FLOW CONSTANT SPEED OPERATING POINT SYSTEM CURVE #1 SYSTEM CURVE #2 18 9
Variable-flow constant-pressure TOTAL HEAD (FT.) 240 220 30 40 50 60 CONSTANT SPEED 70 75 OPERATING POINT 200 78 80 180 100% SPEED 160 REDUCED SPEED OPERATING POINT 140 90% SPEED 120 100 80 60 40 20 PUMP OUTPUT POWER = HEAD x FLOW x SPECIFIC GRAVITY 3960 BYPASS LOSSES 0 200 400 600 800 1000 1200 1400 1600 1800 FLOW (GPM) MAIN FLOW BYPASS FLOW TOTAL FLOW 19 Variable-flow constant-pressure 80 70 BYPASS OPERATION WITH STANDARD EFFICIENT MOTOR 60 50 ADJUSTABLE SPEED OPERATION WITH ENERGY EFFICIENT MOTOR INPUT KW 40 30 20 10 0 500 700 900 1100 1300 1500 1700 FLOW (GPM) 20 10
Comparison of two pumping systems 21 Two-Stages Pumping System 22 11
Benefits High availability Fast and precise control Minimized energy consumption Reduced emission Minimized actuator equipment Soft starting 23 Power Consumption 24 12
Investment and Energy Costs Energy is calculating for 1300 kw motor and 3 years operation 25 Fans 26 13
Rotary screw air compressor 27 Lifts 28 14
Lift Energy Comparison 29 Mechanical Conveyor Belt Load Centrifugal-Acting In-Line Fluid Coupling Full-Speed AC Motor 30 15
Mechanical V-Belt Hand crank opens and closes sheave to move belt up or down. Belt rides up or down based on groove setting Available up to 100 kw 31 Mechanical Operator-Controller Potentiometer for Speed Selection Motorized Speed Changer Prime Mover AC Motor Reduced-Speed Output Full-Speed Input PIV Transmission Box 32 16
Conventional Full-Speed AC Motor Full-Speed Shaft Variable-Speed Shaft Magnetic field for Flux Control Field Control Speed Potentiometer 33 Conventional Variable Speed DC Drives Generator Motor AC source Motor 3φ G M Load Exciter 34 17
Modern Variable Speed DC Drives Four - Quadrant Converter Motor AC source M Load Field supply 35 Conventional Variable Speed AC Drives Pole changing Stator voltage control Rotor resistance control Slip-recovery drive system 36 18
Modern Variable Speed AC Drive System Variable- voltage variable- frequency AC supply AC source AC - AC Converter 3φ AC Motor 37 Advantages of Variable Speed AC Drives Commutatorless and brushless High-power and high-speed Simple design and robust High-efficiency 38 19
Classifications of Variable Speed AC Drives Motor types : induction and synchronous motors Power supplies : inverter, cycloconverter, matrix converter. Inverter types : voltage source, current source, square type, PWM. 39 Variable Voltage Inverter System Smoothing inductor AC source Smoothing capacitor v out AC Motor 3φ Controlled rectifier Square - wave inverter DC voltage is variable and controlled by the rectifier. The output voltage of inverter is quasi square-wave. The output frequency is determined by the inverter. The output voltage is determined by the rectifier. An LC filter is required in the dc link. 40 20
PWM Inverter System AC source AC Motor Smoothing capacitor v out 3φ Uncontrolled rectifier PWM inverter The dc voltage is constant. No controller is required by the rectifier. The inverter is controlled by pulse width modulation (PWM) technique. The output current is almost sinusoidal. The output voltage and frequency are controlled by the inverter. Only a dc capacitor is used as the filter in the dc link. 41 Current Source Inverter System Smoothing inductor AC source AC Motor 3φ i out Controlled rectifier Square - wave inverter The dc link current is controlled by the rectifier. The inverter output current is quasi square-wave. The output current frequency is controlled by the inverter. The magnitude of the output current is controlled by the rectifier. Only an inductor is used as the filter in the dc link. 42 21
Six-Pulse CSI System 43 Twelve-Pulse CSI System 44 22
PWM CSI System 45 Cycloconverter System AC source AC Motor No dc link. The output voltage magnitude and frequency are controlled by the cycloconverter. The output frequency is less than the ac supply frequency. 46 23
Load Commutated Inverter System Smoothing inductor AC source AC Synchronous Motor 3φ i out Controlled rectifier Load commutated inverter The dc link current is controlled by the inverter. The output current waveform is quasi square-wave. The thyristors of inverter are commutated by the help of load voltage. The inverter frequency is determined by the motor speed. 47 Large LCI System 48 24
Slip Recovery Induction Drive Wound rotor induction motor AC source Inverter Rectifier Converter rating is smaller than motor rating Only subsynchronous operation is possible Wound rotor motor is required 49 VSD with Unity Power Factor Rectifier C d L boost L in C in IM Input current waveform is almost sinusoidal and unity power factor Insensitive to input voltage variation Applicable up to 100 kw 50 25
VSD with PWM Rectifier PWM rectifier PWM inverter C d AC source Power flow is bidirectional Input current waveform is almost sinusoidal Input power factor is adjustable Insensitive to input voltage variations IM 51 Matrix Converter AC source IM No dc link Output frequency is less than the input frequency Input current is almost sinusoidal Input power factor is adjustable 52 26
Additional Advantages of using VSD Soft starting (reducing system kva requirement and lengthening rotating equipment life). Increased motor life Shortened compressor startup time Process ride through Increased speed range Extended operating range before surge line Suitable for automation Can be used to overpowering the equipment without endangering the motor 53 Medium Voltage ABB Drives 54 27
Toshiba System 55 VSD Price 56 28
Technical Barriers VSD may reduce the motor efficiency VSD draws nonsinusoidal input current VSD may induce overvoltage to motor winding when the cable is longer than 50 meters VSD may induce bearing currents VSD may overloading shunt capacitor in the supply system Special technicians, engineers, and operators may required 57 Motor efficiencies 95 100 HP ENERGY EFFICIENT MOTOR 60 HZ 60 HZ 90 30 HZ 60 HZ % EFFICIENCY 85 100 HP STANDARD EFFICIENT MOTOR 60 HZ 30 HZ 80 0 0 25 50 75 100 % FULL-LOAD TORQUE 58 29
Chances to save energy Are there motors that drive fans, pumps, or compressors which are modulated by dampers or valve? Are there motor using speed control devices? Is there machinery that can be operated at other than its current speed? For the motors identified by the above three questions, what is the duty cycle and load profile? 59 Power Line Considerations 60 30
Power Line Considerations 61 Power Line Considerations 62 31
Power Line Considerations 63 Implementation cost factors How will the VSD improve quality? What costs associated with existing motor drive inefficiencies? What are the costs of maintaining existing equipment? Are they obsolete and in need of replacement? Do other problems of equipment reliability cause production delays and higher production costs? How can they be eliminated by VSDs with self-diagnostic features? Is there opportunity to create additional space by removing large mechanical equipment with the installation of VSD? Can plant noise be reduced by using VSD? What shutdown arrangements are required to provide time to install a VSD? 64 32
Factors that influence first cost Rectifier and inverter type Harmonic effects Isolation requirements Control specifications Special requirements Training requirements 65 Thank You 33