Elevator DrivesPast, 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

History236 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

1882-1889 – Tesla AC Induction Motor 3-Phase Squirrel Cage Design

1889 – Otis Elevator Uses DC Motor

Otis DC

Elevator Motor

Circa 1889

History1891 – Ward Leonard Variable

Speed Control– AC Induction Motor Turning DC Dynamo

– Rheostat to Control Generated Voltage

– DC Voltage Controls DC Motor Speed

1900-1970’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 84 26 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 10-40 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

1.0

0

-1.0

-2.5

2.5POWER

KILOWATTS

FULL CAR

EMPTY CAR

EMPTY CAR

FULL CAR

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 / 12-45 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

– 45-600 HP / 34-450 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 No

Unity Pwr

Factor

No No

Drive Type Comparison

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 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.