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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
Lecture - 16 Dc Motor Speed Control - Introduction
Lecture - 16 Dc Motor Speed Control - Introduction
::2008/04/17::
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4
Ward Leonard Varistat Dimmer
Ward Leonard Varistat Dimmer
::2012/06/14::
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5
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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6
15112012034 grupo ward leonard
15112012034 grupo ward leonard
::2013/02/06::
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7
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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8
Schindler Ward Leonard gearless machines with Aconic controllers
Schindler Ward Leonard gearless machines with Aconic controllers
::2011/01/13::
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9
Ward Leonard 02
Ward Leonard 02
::2011/04/07::
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10
Ward Churchill Interview on Leonard Peltier
Ward Churchill Interview on Leonard Peltier
::2012/06/24::
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11
Conexion Ward leonard... sencillamente explicado
Conexion Ward leonard... sencillamente explicado
::2013/07/17::
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12
Aufzugsteuerung mit Leonardsatz
Aufzugsteuerung mit Leonardsatz
::2008/10/24::
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13
Leonard Ward - Quit Smoking
Leonard Ward - Quit Smoking
::2010/05/26::
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14
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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15
Gary Ward Tape 1 Track 1 and 2
Gary Ward Tape 1 Track 1 and 2
::2014/05/02::
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16
Gary Ward Tape 2 Tracks 1 and 2
Gary Ward Tape 2 Tracks 1 and 2
::2014/05/03::
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17
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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18
Funicular Mountain Tram Elevator in Prague of Europe
Funicular Mountain Tram Elevator in Prague of Europe
::2014/01/14::
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19
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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20
(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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21
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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22
Ward Churchill loses composure in Hawaii
Ward Churchill loses composure in Hawaii
::2006/11/11::
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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 1)
::2011/05/21::
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25
Penny & Leonard ~Teenage Dream~
Penny & Leonard ~Teenage Dream~
::2014/02/10::
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26
Ron Lyle vs Stan Ward
Ron Lyle vs Stan Ward
::2012/11/16::
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27
Brother Darrell Ward
Brother Darrell Ward
::2013/05/05::
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28
When They Came After Ward Churchill part 5
When They Came After Ward Churchill part 5
::2009/03/02::
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29
Slowly Fallin
Slowly Fallin' original song by Hannah Ward, lyrics in description
::2013/09/25::
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30
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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31
Mind Control
Mind Control
::2011/03/02::
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32
Ward: I Wanted It To Be A Person
Ward: I Wanted It To Be A Person
::2013/11/16::
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33
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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34
Lec-10 Control System Sensitivity
Lec-10 Control System Sensitivity
::2008/08/25::
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35
DC lift motor
DC lift motor
::2008/07/04::
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36
Granville Taylor Woods Patent No 373383 Video Segment 3
Granville Taylor Woods Patent No 373383 Video Segment 3
::2012/01/02::
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37
Donna Summer - Love Has A Mind Of Its Own
Donna Summer - Love Has A Mind Of Its Own
::2011/11/06::
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38
Are Andre Berto and Andre Ward injury related?
Are Andre Berto and Andre Ward injury related?
::2013/08/17::
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39
REINCARNATION of Jesus/Shroud~ Brian Leonard Golightly Marshall
REINCARNATION of Jesus/Shroud~ Brian Leonard Golightly Marshall
::2011/12/16::
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40
Vocal Microphone Shootout at Ward Brodt with Joe Anderson
Vocal Microphone Shootout at Ward Brodt with Joe Anderson
::2013/04/25::
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41
Melvin Leonard - You Got To Move Your Body
Melvin Leonard - You Got To Move Your Body
::2011/08/01::
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42
Jim Farey & Billy Ward @ PASIC 2011
Jim Farey & Billy Ward @ PASIC 2011
::2011/11/19::
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43
TOP SIDE CONTROL Maintaining Position
TOP SIDE CONTROL Maintaining Position
::2014/04/03::
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44
La casta del doppiaggio italiano
La casta del doppiaggio italiano
::2013/11/22::
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45
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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46
IndraDrive Mi with 3rd Party Control
IndraDrive Mi with 3rd Party Control
::2011/03/29::
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47
Vera Ward Hall, Dock Reed, and Henry Reed - Moaning (I
Vera Ward Hall, Dock Reed, and Henry Reed - Moaning (I'll Soon Be Gone)
::2014/09/17::
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48
Free Leonard Peltier Now! (WA/HA? 2000) Winner Bronze at Houston Worldfest 2001
Free Leonard Peltier Now! (WA/HA? 2000) Winner Bronze at Houston Worldfest 2001
::2012/07/06::
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49
Sta.Ge HELLAS GEARLESS LIFT CONTROL PANEL
Sta.Ge HELLAS GEARLESS LIFT CONTROL PANEL
::2009/10/21::
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50
BREAKING NEWS AMRERICA! HERE IS HOW TO WARD OFF  NIBIRU TORNADO ASSAULTS ON YOU. NO MYSTERY TO IT.
BREAKING NEWS AMRERICA! HERE IS HOW TO WARD OFF NIBIRU TORNADO ASSAULTS ON YOU. NO MYSTERY TO IT.
::2011/04/27::
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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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