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1
Ward Leonard Corporate Video
Ward Leonard Corporate Video
::2014/01/23::
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2
Ward Leonard 01
Ward Leonard 01
::2011/04/07::
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3
Ward Leonard Varistat Dimmer
Ward Leonard Varistat Dimmer
::2012/06/14::
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4
Lecture - 16 Dc Motor Speed Control - Introduction
Lecture - 16 Dc Motor Speed Control - Introduction
::2008/04/17::
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5
15112012034 grupo ward leonard
15112012034 grupo ward leonard
::2013/02/06::
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6
Ward Leonard 2,000 HP AC Induction Motor Video
Ward Leonard 2,000 HP AC Induction Motor Video
::2014/05/05::
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7
Aufzug Antrieb  Ward Leonard
Aufzug Antrieb Ward Leonard
::2013/11/11::
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8
Dicky Eklund ward knocks down Sugar Ray Leonard the fighter real !!!
Dicky Eklund ward knocks down Sugar Ray Leonard the fighter real !!!
::2011/01/01::
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9
Schindler Ward Leonard gearless machines with Aconic controllers
Schindler Ward Leonard gearless machines with Aconic controllers
::2011/01/13::
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10
Conexion Ward leonard... sencillamente explicado
Conexion Ward leonard... sencillamente explicado
::2013/07/17::
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11
Ward Leonard 02
Ward Leonard 02
::2011/04/07::
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12
Ward Churchill Interview on Leonard Peltier
Ward Churchill Interview on Leonard Peltier
::2012/06/24::
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13
Ward Léonard : Présentation + Intro + Les Costards (Live Montereau Confluence 2012)
Ward Léonard : Présentation + Intro + Les Costards (Live Montereau Confluence 2012)
::2012/06/10::
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14
Otis 1970
Otis 1970's Highspeed, Gearless, relay controlled Elevators (A semi showcase + cheeky manual call)
::2011/05/18::
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15
Leonard Ward - Quit Smoking
Leonard Ward - Quit Smoking
::2010/05/26::
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16
Legendary Nights Sugar Ray Leonard vs Thomas Hagler The Super Fight
Legendary Nights Sugar Ray Leonard vs Thomas Hagler The Super Fight
::2013/11/30::
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17
Ward -v- Irwin, Pool, IPA Tour Nottingham
Ward -v- Irwin, Pool, IPA Tour Nottingham
::2014/09/10::
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18
Aufzugsteuerung mit Leonardsatz
Aufzugsteuerung mit Leonardsatz
::2008/10/24::
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19
Funicular Mountain Tram Elevator in Prague of Europe
Funicular Mountain Tram Elevator in Prague of Europe
::2014/01/14::
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20
Ward Churchill - Lecture (Unedited) @ Burning Books, Buffalo, NY (2013-05-22)
Ward Churchill - Lecture (Unedited) @ Burning Books, Buffalo, NY (2013-05-22)
::2013/06/22::
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21
Sugar Ray Leonard on Mayweather: He
Sugar Ray Leonard on Mayweather: He's Still the Best
::2014/06/06::
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22
BluesTune: Mark Leonard & Bill Champlin, Bruce Gaitsch, B. Ward
BluesTune: Mark Leonard & Bill Champlin, Bruce Gaitsch, B. Ward
::2011/04/16::
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23
When They Came After Ward Churchill part 1
When They Came After Ward Churchill part 1
::2009/03/02::
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24
(Now extinct) FASCINATING 1970
(Now extinct) FASCINATING 1970's DMR lift control system by Express Lifts + MOTOR ROOM (Part 2)
::2011/05/22::
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25
Lorenzo Ward after Sept. 18 Gamecocks practice
Lorenzo Ward after Sept. 18 Gamecocks practice
::2014/09/18::
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26
Scrubs
Scrubs 'Leonard: Half Kitten, Half Monkey'
::2007/04/11::
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27
Amy Goodman Interviews Leonard Peltier From Prison
Amy Goodman Interviews Leonard Peltier From Prison
::2012/12/19::
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28
(Now extinct) FASCINATING 1970
(Now extinct) FASCINATING 1970's DMR lift control system by Express Lifts + MOTOR ROOM (Part 1)
::2011/05/21::
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29
Brother Darrell Ward
Brother Darrell Ward
::2013/05/05::
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30
Penny & Leonard ~Teenage Dream~
Penny & Leonard ~Teenage Dream~
::2014/02/10::
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31
Slowly Fallin
Slowly Fallin' original song by Hannah Ward, lyrics in description
::2013/09/25::
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32
and x202a;Fight Gypsy GARETH vs WARD Bareknuckle Boxing 2013 and x202c; and rlm;   YouTube
and x202a;Fight Gypsy GARETH vs WARD Bareknuckle Boxing 2013 and x202c; and rlm; YouTube
::2014/05/12::
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33
When They Came After Ward Churchill part 5
When They Came After Ward Churchill part 5
::2009/03/02::
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34
Mind Control
Mind Control
::2011/03/02::
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35
Who control the American military? Who owns their allegience? Who
Who control the American military? Who owns their allegience? Who's order have priority?
::2012/06/20::
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36
Leonard Charles - Wake Up Now Testimonial #SelflessFounders
Leonard Charles - Wake Up Now Testimonial #SelflessFounders
::2014/04/17::
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37
Andre Ward trains smart and boring - He is a Gold Medalist & Undefeated as a Pro
Andre Ward trains smart and boring - He is a Gold Medalist & Undefeated as a Pro
::2013/11/18::
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38
Doing Time: The Politics of Imprisonment - Lecture by Ward Churchill (Part 1)
Doing Time: The Politics of Imprisonment - Lecture by Ward Churchill (Part 1)
::2011/06/02::
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39
Little Elm Fire Department Clowns on Fire presents:  Despicable Clowns on Fire 2013
Little Elm Fire Department Clowns on Fire presents: Despicable Clowns on Fire 2013
::2013/12/30::
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40
EGO Thoughts: Amir Khan says Mayweather cannot Dictate Him or Control Him *LOL WHAT*
EGO Thoughts: Amir Khan says Mayweather cannot Dictate Him or Control Him *LOL WHAT*
::2013/11/28::
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41
Leonard Nimoy Laserdisc Demo (2 of 3) BEST QUALITY
Leonard Nimoy Laserdisc Demo (2 of 3) BEST QUALITY
::2010/04/14::
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42
Lec-10 Control System Sensitivity
Lec-10 Control System Sensitivity
::2008/08/25::
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43
|You and I, we
|You and I, we'll be young forever||Multifandom|
::2011/04/16::
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44
part of 1992 Montgomery Ward instore laserdisc
part of 1992 Montgomery Ward instore laserdisc
::2010/05/09::
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45
A.M. Leonard
A.M. Leonard's Tool Story
::2013/09/05::
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46
Ed Ward Video Testimonial
Ed Ward Video Testimonial
::2014/04/22::
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47
Valves, Instrumentation, and Control
Valves, Instrumentation, and Control
::2014/07/03::
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48
Are Andre Berto and Andre Ward injury related?
Are Andre Berto and Andre Ward injury related?
::2013/08/17::
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DC lift motor
DC lift motor
::2008/07/04::
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TOP SIDE CONTROL Maintaining Position
TOP SIDE CONTROL Maintaining Position
::2014/04/03::
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RESULTS [51 .. 101]
From Wikipedia, the free encyclopedia
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Ward Leonard Control, also known as the Ward Leonard Drive System, was a widely used DC motor speed control system introduced by Harry Ward Leonard in 1891. In early 1900s, the control system of Ward Leonard was adopted by the U.S. Navy and also used in passenger lift of large mines. It also provided a solution to a moving sidewalk at the Paris Exposition of 1900, where many others had failed to operate properly.[citation needed] It was applied to railway locomotives used in World War 1, and was used in anti-aircraft radars in World War 2. Connected to automatic anti-aircraft gun directors, the tracking motion in two dimensions had to be extremely smooth and precise. The MIT Radiation Laboratory selected Ward-Leonard to equip the famous radar SCR-584 in 1942. The Ward Leonard control system was widely used for elevators until thyristor drives became available in the 1980s, because it offered smooth speed control and consistent torque. Many Ward Leonard control systems and variations on them remain in use.[1]

Basic concept[edit]

The key feature of the Ward Leonard control system is the ability to smoothly vary the speed of a DC motor, including reversing it, by controlling the field windings and hence the output voltage of a DC generator. As the speed of a DC motor is dictated by the supplied voltage, this gives simple speed control. The DC generator could be driven by any means, provided that also supplied a voltage source for the field windings. This 'prime mover' could be an AC motor, or it could be an internal combustion engine (its application to vehicles was patented by H.W. Leonard in 1903[2]).

A Ward Leonard drive can be viewed as a high-power amplifier in the multi-kilowatt range, built from rotating electrical machinery. Where the 'prime mover' is electrical, a Ward Leonard drive unit consists of a motor and generator with shafts coupled together. The prime mover, which turns at a constant speed, may be AC or DC powered. The generator is a DC generator, with field windings and armature windings. The input to the amplifier is applied to the field windings, and the higher power output comes from the armature windings. (See Excitation (magnetic)#Amplifier principle for how a generator can act as an amplifier.) The amplifier output is usually connected to a second motor, which moves the load, such as an elevator. With this arrangement, small changes in current applied to the input, and thus the generator field, result in large changes in the output, allowing smooth speed control.[3]

A flywheel may be used to reduce voltage fluctuations during sudden load changes. The Ward Leonard system with this modification is known as Ward Leonard Ilgner Control.[4]

A more technical description[edit]

A Ward Leonard Control system with generator and motor connected directly.

The speed of motor is controlled by varying the voltage fed to the generator field windings, Vgf, which varies the output voltage of the generator. The varied output voltage will change the voltage of the motor, since they are connected directly through the armature. Consequently changing the Vgf will control the speed of the motor. The picture of the right shows the Ward Leonard control system, with the Vgf feeding the generator and Vmf feeding the motor.[5]

Transfer function[edit]

The first subscripts 'g' and 'm' each represents generator and motor. The superscripts 'f', 'r',and 'a', correspond to field, rotor, and armature.

  • W_i = plant state vector
  • K = gain
  • t = time constant
  • J = polar moment of inertia
  • D = angular viscous friction
  • G = rotational inductance constant
  • s = Laplace operator

Eq. 1: The generator field equation

V_g^f = R_g^f I_g^f + L_g^f I_g^f

Eq. 2: The equation of electrical equilibrium in the armature circuit

-G_g^fa I_g^f W_g^r + (R_g^a + R_m^a) I^a + (L_g^a + L_m^a) I^a + G_m^fa I_m^f W_m^r = 0

Eq. 3: Motor torque equation

-T_L = J_m W_m^r + D_mW_m^r

With total impedance, L_g^a + L_m^a, neglected, the transfer function can be obtained by solving eq 3 T_L = 0.

Eq. 4: Transfer function

\frac{W_m^r(S)}{V_g^f(S)} = \cfrac{K_BK_v/D_m}{\left(t_g^fs + 1\right)\left(t_ms + \frac{K_m}{D_m}\right)}[5]

with the constants defined as below:

K_B = \frac{G_m^fa V_m^f}{R_m^f(R_g^a + R_m^a)}
K_v = \frac{G_g^fa W_g^r}{R_g^f}
t_m = \frac{J_m}{D_m}
t_g^f = \frac{L_g^f}{R_g^f}
K_m = D_m + K_B^2(R_g^a + R_m^a)

See also[edit]

References[edit]

Citations
  1. ^ Kulkarni, A.B. (Oct 2000). "Energy consumption analysis for geared elevator modernization: upgrade from DC Ward Leonard system to AC vector controlled drive". "Conference Record of the 2000 IEEE Industry Applications Conference" 4. Institute of Electrical and Electronics Engineers. pp. 2066–2070. 
  2. ^ "Electrically propelled Vehicle", H.W. Leonard, US Patent 1121382, originally filed March, 1903
  3. ^ Shinners, Stanley M (1998). Modern Control System Theory. Wiley and Sons. p. 202. ISBN 978-0471249061. 
  4. ^ Rajput, R.K. (2005). Basic Electrical Engineering. Laxmi Publications Pvt Limited. p. 571. ISBN 9788170081203. Retrieved 2014-06-14. 
  5. ^ a b Datta, A.K. (1973). "Computerless optimal control of Ward Leonard drive system". International Journal of Systems Science 4 (4): 671–678. doi:10.1080/00207727308920047. 
General references
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