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1
Ward Leonard 01
Ward Leonard 01
::2011/04/07::
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Ward Leonard Corporate Video
Ward Leonard Corporate Video
::2014/01/23::
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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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Ward Leonard Varistat Dimmer
Ward Leonard Varistat Dimmer
::2012/06/14::
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15112012034 grupo ward leonard
15112012034 grupo ward leonard
::2013/02/06::
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Aufzug Antrieb  Ward Leonard
Aufzug Antrieb Ward Leonard
::2013/11/11::
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7
Lecture - 16 Dc Motor Speed Control - Introduction
Lecture - 16 Dc Motor Speed Control - Introduction
::2008/04/17::
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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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Schindler Ward Leonard gearless machines with Aconic controllers
Schindler Ward Leonard gearless machines with Aconic controllers
::2011/01/13::
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Ward Leonard 02
Ward Leonard 02
::2011/04/07::
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11
Conexion Ward leonard... sencillamente explicado
Conexion Ward leonard... sencillamente explicado
::2013/07/17::
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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
Leonard Ward - Quit Smoking
Leonard Ward - Quit Smoking
::2010/05/26::
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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
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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16
Jessalyn Ward - Tears of An Angel
Jessalyn Ward - Tears of An Angel
::2014/07/29::
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17
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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18
Lorenzo Ward after Sept. 18 Gamecocks practice
Lorenzo Ward after Sept. 18 Gamecocks practice
::2014/09/18::
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19
Valves, Instrumentation, and Control
Valves, Instrumentation, and Control
::2014/07/03::
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20
GODLESS - Who
GODLESS - Who's In Control 1992 [FULL ALBUM]
::2014/08/07::
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TOP SIDE CONTROL Maintaining Position
TOP SIDE CONTROL Maintaining Position
::2014/04/03::
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Sugar Ray Leonard on Mayweather: He
Sugar Ray Leonard on Mayweather: He's Still the Best
::2014/06/06::
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23
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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24
How Money Controls Politics: Thomas Ferguson Interview
How Money Controls Politics: Thomas Ferguson Interview
::2014/05/04::
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25
Andre Ward M.I.A.
Andre Ward M.I.A.
::2014/08/28::
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26
Sugar Ray Leonard - Augustin Estrada. 1977-11-05
Sugar Ray Leonard - Augustin Estrada. 1977-11-05
::2014/09/10::
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Penny & Leonard ~Teenage Dream~
Penny & Leonard ~Teenage Dream~
::2014/02/10::
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28
Flood Control in the Netherlands.Dredging operations that create new lands: Ooste...HD Stock Footage
Flood Control in the Netherlands.Dredging operations that create new lands: Ooste...HD Stock Footage
::2014/06/21::
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29
LED Dimmer as motor controller for the modeler and hobbyist
LED Dimmer as motor controller for the modeler and hobbyist
::2012/12/22::
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30
TOP SIDE CONTROL Baseball Bat Choke Samurai Choke with Matt Andrews
TOP SIDE CONTROL Baseball Bat Choke Samurai Choke with Matt Andrews
::2014/04/03::
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31
Leonard Charles - Wake Up Now Testimonial #SelflessFounders
Leonard Charles - Wake Up Now Testimonial #SelflessFounders
::2014/04/17::
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32
Ed Ward Video Testimonial
Ed Ward Video Testimonial
::2014/04/22::
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33
Ward Churchill loses composure in Hawaii
Ward Churchill loses composure in Hawaii
::2006/11/11::
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34
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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35
Slowly Fallin
Slowly Fallin' original song by Hannah Ward, lyrics in description
::2013/09/25::
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36
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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37
Side Control Escape Basic Hip Movement
Side Control Escape Basic Hip Movement
::2014/04/03::
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38
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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39
TOP SIDE CONTROL Paper Cutter Choke with Matt Andrews
TOP SIDE CONTROL Paper Cutter Choke with Matt Andrews
::2014/04/03::
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40
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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41
"Ward 13 with Jon Hopwood" Featuring Joel Elber & Peter White
"Ward 13 with Jon Hopwood" Featuring Joel Elber & Peter White
::2014/09/04::
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42
A.M. Leonard
A.M. Leonard's Tool Story
::2013/09/05::
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Explaining Ward and Milling of a Key
Explaining Ward and Milling of a Key
::2014/05/19::
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Dr Leonard Sacks - DNDi 10-Year Paris Event 2013
Dr Leonard Sacks - DNDi 10-Year Paris Event 2013
::2013/12/19::
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ANITA WARD  -  Ring My Bell  (1979)
ANITA WARD - Ring My Bell (1979)
::2013/09/18::
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D C Motor Speed relation with field flux edited
D C Motor Speed relation with field flux edited
::2013/05/20::
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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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(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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11-5963 oral arguments embody v ward federal 6th circuit gun rights fourth amendment firearms
11-5963 oral arguments embody v ward federal 6th circuit gun rights fourth amendment firearms
::2012/07/26::
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Brother Darrell Ward
Brother Darrell Ward
::2013/05/05::
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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]

Mathematical approach[edit]

Among many ways of defining the characteristic of a system, obtaining a transfer characteristic is one of the most commonly used methods. Below are the steps to obtain the transfer function, eq. 4.

Before going into the equations, first conventions should be set up, which will follow the convention data used. 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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