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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