Elevator Drives Past, Present and Future As Presented at NAVTP Annual Forum Atlanta, Georgia May 3, 2007

Elevator Drives - Discussion  History  Requirements  Motor and Control Types  Industry Trends  Future Drives

History  236 BC – First Passenger Lift, Archimedes  1853 – Safe Elevator Demo, Elisha Otis  1857 – First Safe Elevator Installation, Cooper Union, NYC  1861 – Otis Elevator Patent

Otis Patent 1861

History  1873 – First Modern DC Motor  1874 – J. W. Meaker Door Opener Patent  1880 – First Electric Motor Controlled Elevator Siemens / Sprague  – Tesla AC Induction Motor 3-Phase Squirrel Cage Design  1889 – Otis Elevator Uses DC Motor

Otis DC Elevator Motor Circa 1889

History  1891 – Ward Leonard Variable Speed Control –AC Induction Motor Turning DC Dynamo –Rheostat to Control Generated Voltage –DC Voltage Controls DC Motor Speed  ’s – Ward-Leonard M-G Sets and DC Motors Used for Variable Speed Elevators  AC Motors Used 1 and 2 Speed Starters

Otis No. 1 Geared DC Machine with DC Motor Circa 1915

Otis Gearless DC Machine Circa 1919

M-G Set Controls (Otis Elevator, 1920’s)

Otis Type Broadway,NYC Circa 1930’s

History  1975-Present –Thyristor (SCR) DC Drives Control Elevators –All Analog Components in the 70’s –Replaces Aging M-G Sets  1980’s – Microprocessors Improve –Car Dispatch and Motor Drive Controllers

Otis type 84,NYC with Encoder

Westinghouse #205 with Encoder

History  Late 1980’s – –Variable Frequency Inverters AC Induction Motors, Geared Applications Only  Early 1990’s – –More AC Inverters and Motors Begin to Displace Small DC, 3-15 HP  Mid-1990’s – –Vector Control AC Inverters HP Almost as Good as SCR-DC. –KONE Introduces PM EcoDisc AC Machine

History – Custom Gearless AC Induction Machines – First Fully Regenerative AC Elevator Drives – Much Discussion on PM-AC and MRL – SCR-DC Still Used for Medium and Large Building Mods  Late 1990’s –

History – More PM-AC Motor Manufacturers. PM Gearless Begins to Replace AC Geared – EU Focus on Efficiency and Harmonics/EMC – Lower Cost IGBT Inverter Components – North America Begins to Focus on Energy Reduction – New Construction Leaning toward AC – SCR-DC Still Used on Medium-Large Building Mods  2000-Present –

Elevator Drive Requirements

Elevator Duty Cycle

Four Quadrant Operation

What Customers Want  Repeatable Elevator Performance  Smooth Operation  Reliable Operating Life  Effortless Installation  Custom Control Interface  High Efficiency  Conformance to All Codes  Low Installed Cost

Elevators vs. Industrial Applications  Infinitely Variable Speed Range  Infinitely Variable Torque Range with Smooth Bump Less Operation  Millions of Repeated Operating Cycles with High Peak Torque  High Inertia Resonant Load  Accurate Stopping Position  Unattended Operation 24/7/365

Elevators vs. Industrial Applications  Quiet Operation  Long Operating Life  Long-Term Product Support

Types of Motors  DC Shunt Field –High Speed Geared –Low Speed Gearless –Full HP Range 5 – 600 HP –89–94% Efficient –High Torque Capacity Accel/Decel –In Elevator Service for 70+ Years –Requires DC Generator, SCR or Other AC-DC Power Conversion from AC Utility Power –DC Motor Can Act Like a Generator

Types of Motors  AC Induction –High Speed Geared, 2–75 HP –Few Low Speed Designs for Gearless –85–94% Efficient –Many with Single or 2 Speed Starters –Can be Variable Speed by Inverter Control of Frequency –Torque Strength Derived from Out of Phase Excitation Current –Requires Flux Vector Control for Wide Operating Speed Range –Can Act Like a Generator

Types of Motors  AC Permanent Magnet (PM) –New Designs for Compact Gearless Machines –Torque Strength from Permanent Magnets –90–95% Efficient –Compatible with Inverters to Control Speed –Requires Synchronous Flux Vector / Angle Control to Regulate / Modulate Torque –Supply Limited to Specialty Machine Builders –Not Suitable for High rpm Speed Geared Designs –Can Act Like a Generator

Modernization  Why keep a DC machine? –Many large DC machines cannot be easily replaced with AC. –Large Installed Base of DC Machines Worldwide –DC Motors and Machines are in Good Working Order and Provide Excellent Ride Quality

Large DC Machines Otis 72 and 269

Types of Motor Drives For DC Motors  M-G Set  SCR-DC  PWM-DC For AC Motors  Variable Voltage  V V V F Inv. (V/Hz) Open/Closed Loop  Vector Control Inv. Open/Closed Loop  Synchronous PM Inv. Closed Loop  Regen or Non-Regen

Elevator Power Consumption …the need for Regeneration  Horsepower = Torque x Speed  Gearless Friction Losses are 10-20% of Elevator HP Rating  Moving inertia absorbs energy during acceleration that must be removed during deceleration.  Mechanical, electric and electronic losses are proportional to torque or current flow.  Energy Wasted / Dissipated During Deceleration = Heat  Excessive heat in control rooms must be removed.

–Drive type makes little difference in overall energy consumption. –If DC, Good Candidate for Conversion to AC by Replacing Motor –Low Installed Cost is Usual Critical Issue Practical Energy Considerations  Low Speed Elevators 50–150 fpm –Almost Always Geared… or PM Gearless –Low Speed Usually Means Low Power 2-35 HP / 2-25 kW –Most power is consumed by frictional losses. –True regeneration is not critical. –High Gearbox Losses During Regeneration

Practical Energy Considerations  Medium Speed Elevators 150–450 fpm –Geared and Some Gearless… Including PM –15-60 HP / kW –Lower Frictional Losses in Gearbox –Recovery of inertia energy becomes important, particularly with gearless. –Resistive Braking Still Possible but Need to Perform Heat Load Calculations for Equipment Room

Practical Energy Considerations  High Speed Elevators 500-1,600+ fpm –Low Friction Gearless – HP / kW or Larger –True Regeneration is Mandatory

Industry Trends  Energy Consumption Reduction –kW-hrs / Month –Harmonics, Power Factor  Performance –Reduced Floor–Floor Time –Reduced Vibration  Low Maintenance –Cleanliness  Larger PM Machines –More Gearless Applications

Energy Consumption  Elevator Speed and Payload  Frequency of Use  Hoist Way Efficiency  Motor Efficiency  Power Conversion Efficiency  Idle Losses  Regeneration

Desired Feature SCR-DC Diode – PWM Inv PWM - PWM Installed Cost Smallest vol. Wt. External XFMR Pwr conv efficiency 90% w/ XFMR 93-96%92-94% Drive Type Comparison

Desired Feature SCR-DC Diode – PWM Inv PWM - PWM Regen- eration No Low Harmonics No Unity Pwr Factor No Drive Type Comparison

Desired Feature SCR-DC Diode – PWM Inv PWM - PWM Flexible Motor V With XFMR Below Vac input Stand-by Friendly No AC / DC Motor No

Future Expectations  More PM Gearless –Low and High Power  More Interest in Energy Conservation –Overall Efficiency –Regeneration  More Restrictions on Harmonics and EMC –Sinusoidal High pf Utility Line Current –All Inclusive Drive Units with Filters

Future Elevator Drives  PWM-PWM Double Converter-Inverter –Regulated Harmonics –Unity pf –Fully Regenerative –Compatible with DC Stand-by Power  PM Operation without Resolver –Electronic Alignment Sensing  Compact All Inclusive Packaging  Works with AC Ind. or PM or DC Motors

World’s Tallest Buildings Magnetek has Elevator Drives in 17 of the 30 tallest buildings in the world.