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

• 1882-1889 – 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

• 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 –

Four Quadrant Operation

Linear power stage

advantages

– simple, low priced controller

– low electromagnetic noise level

– no minimum inductance needed

disadvantages

– high power losses at the final stage at high currents or low motor voltages (PV = R I2)

– for small nominal power up to 100 W

M

R

controllerUT

Vcc

Gnd

LSC

Umot

time

Umot, Imot

Pulsed power stage (PWM)advantages– low power losses– high efficiency– for higher nominal

power

disadvantages– electromagnetic noise

in the radio frequency range

– high power losses in the motor at standstill

– minimum inductance necessary

advantages– low power losses– high efficiency– for higher nominal

power

disadvantages– electromagnetic noise

in the radio frequency range

– high power losses in the motor at standstill

– minimum inductance necessary

M

power stage

Umot

Vcc

Gnd

pulse

generator

ADS,DEC, AECS, DES, MIP, PCU, EPOS

time

cycle time: 20 - 50 s

Umot, Imot

Pulsed power stage: current ripple)LL(f2

VI

chokemotS

ccmax

general measures: reduce motor voltage enhance total inductance

- motor choke in controller

- additional motor choke

enhance PWM frequency

50% 50% 30% 70%

low motor inductance

additional motor choke Umot, Imot

Time scales in control loops

0.02 0.05 0.1 0.2 0.5 1 2 5 10 20 ms

50 20 10 5 2 1 0.5 0.2 0.1 0.05

PWM cycle time

"slow" position controller

position controller MIP

current controller

mechanical time constants

speed controller

speed controller as "link" between fast current controller and a slow position control (PLC)

frequency kHz

cycle time

PWM• PWM(Pulse Width Modulation• Cambiando il duty cycle, la velocità cambierà

Figure : PWM Control Signal

Duty Cycle 20%Lowest Speed

Duty Cycle 50%Middle Speed

Duty Cycle 80%High Speed

Cycle

Duty Cycle

Duty Cycle = DT / T (%)

(DT)

Lo scopo è :Lo scopo è :

1. Ridurre la dissipazione di potenza.1. Ridurre la dissipazione di potenza.

2. Ridurre I problemi di raffreddamento dei transistors)2. Ridurre I problemi di raffreddamento dei transistors)

Duty cycle

• si definisce duty cycle d il rapporto tra la durata del segnale "alto" ed il periodo totaleT del segnale, e serve ad esprimere per quanta porzione di periodo il segnale è a livello alto:

t

Td

• PWMUn segnale PWM (Pulse Width Modulation ovvero modulazione a variazione della larghezza d'impulso) è un' onda quadra di duty cycle variabile che permette di controllare l'assorbimento (la potenza assorbita) di un carico elettrico(nel nostro caso il motore DC), variando modulando) il duty cycle.

• Un segnale PWM è caratterizzato dalla frequenza (fissa) e dal duty cycle (variabile);

• si deduce dalla Figura, il duty cycle è il rapporto tra il tempo in cui l'onda assume valore alto e il periodo T (l'inverso della frequenza: T=1/f)

• Es. un duty cycle dell'80% corrisponde ad un'onda quadra che assume valore alto per l'80% del tempo e basso per il restante 20%,

DC Motor DrivesDC motor speed control using Switching Control or PWM

PWM

Full-bridgeDC-DC

converterDiode

rectifierFilter

capacitor

Pluse-width-modulation

MVoltage Source

VoutVs

Pulse Width%Duty cycle = x 100

Cycle

out s V = % Duty cycle x V

Power Electronic converter

Vcc

Q1

Q4

Q3

Q2G

G

G

GA B

C D

ON

OFF

OFF

ON

M

D1

D4

D3

D2

H-bridge converters circuit