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Ward Leonard 01
Ward Leonard 01
::2011/04/07::
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15112012034 grupo ward leonard
15112012034 grupo ward leonard
::2013/02/07::
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Ward Leonard 2,000 HP AC Induction Motor Video
Ward Leonard 2,000 HP AC Induction Motor Video
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Ward Leonard Varistat Dimmer
Ward Leonard Varistat Dimmer
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Ward Leonard Corporate Video
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Lecture - 21 DC Motor Speed Control Controller Design 3
Lecture - 21 DC Motor Speed Control Controller Design 3
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Aufzug Antrieb  Ward Leonard
Aufzug Antrieb Ward Leonard
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Lecture - 16 Dc Motor Speed Control - Introduction
Lecture - 16 Dc Motor Speed Control - Introduction
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Dicky Eklund ward knocks down Sugar Ray Leonard the fighter real !!!
Dicky Eklund ward knocks down Sugar Ray Leonard the fighter real !!!
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Schindler Ward Leonard gearless machines with Aconic controllers
Schindler Ward Leonard gearless machines with Aconic controllers
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Conexion Ward leonard... sencillamente explicado
Conexion Ward leonard... sencillamente explicado
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Ward Leonard 02
Ward Leonard 02
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Otis 1970
Otis 1970's Highspeed, Gearless, relay controlled Elevators (A semi showcase + cheeky manual call)
::2011/05/18::
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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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Ward Churchill Interview on Leonard Peltier
Ward Churchill Interview on Leonard Peltier
::2012/06/25::
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Leonard Ward - Quit Smoking
Leonard Ward - Quit Smoking
::2010/05/26::
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Funicular Mountain Tram Elevator in Prague of Europe
Funicular Mountain Tram Elevator in Prague of Europe
::2014/01/14::
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Aufzugsteuerung mit Leonardsatz
Aufzugsteuerung mit Leonardsatz
::2008/10/24::
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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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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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Draper
Draper's Role in Space Shuttle Guidance, Navigation & Control, Part 1
::2014/06/05::
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NBA2K14 MID AIR CHANGE SHOT CONTROL TUTORIAL
NBA2K14 MID AIR CHANGE SHOT CONTROL TUTORIAL
::2014/06/29::
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Dialog with Gun Appreciation Day founder Larry Ward
Dialog with Gun Appreciation Day founder Larry Ward
::2012/12/23::
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Side Control Escape Far Side Arm Isolated
Side Control Escape Far Side Arm Isolated
::2014/04/04::
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Granville Taylor Woods Patent No 373383 Video Segment 3
Granville Taylor Woods Patent No 373383 Video Segment 3
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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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Leonard Charles - Wake Up Now Testimonial #SelflessFounders
Leonard Charles - Wake Up Now Testimonial #SelflessFounders
::2014/04/17::
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TOP SIDE CONTROL Maintaining Position
TOP SIDE CONTROL Maintaining Position
::2014/04/04::
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How Money Controls Politics: Thomas Ferguson Interview
How Money Controls Politics: Thomas Ferguson Interview
::2014/05/04::
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Leonard Cohen - Hey, that
Leonard Cohen - Hey, that's no way to say goodbye (Subtitulada / Subtitled)
::2011/09/14::
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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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Former NFL stars Tony Dorsett, Leonard Marshall, Joe DeLameilleure show indicators of CTE resulting
Former NFL stars Tony Dorsett, Leonard Marshall, Joe DeLameilleure show indicators of CTE resulting
::2013/11/07::
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Ed Ward Video Testimonial
Ed Ward Video Testimonial
::2014/04/22::
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Laura Branigan - Self Control - Acapella
Laura Branigan - Self Control - Acapella
::2013/12/30::
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Amy Goodman Interviews Leonard Peltier From Prison
Amy Goodman Interviews Leonard Peltier From Prison
::2012/12/19::
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Dr Leonard Sacks - DNDi 10-Year Paris Event 2013
Dr Leonard Sacks - DNDi 10-Year Paris Event 2013
::2013/12/20::
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TOP SIDE CONTROL Collar Choke with Kris Kim
TOP SIDE CONTROL Collar Choke with Kris Kim
::2014/04/04::
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TOP SIDE CONTROL Baseball Bat Choke Samurai Choke with Matt Andrews
TOP SIDE CONTROL Baseball Bat Choke Samurai Choke with Matt Andrews
::2014/04/04::
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Ward Churchill loses composure in Hawaii
Ward Churchill loses composure in Hawaii
::2006/11/12::
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Idle Chatter: Episode 003
Idle Chatter: Episode 003
::2014/04/30::
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Shane Mosley says Gennady Golovkin vs. Andre Ward is a great megafight for the future
Shane Mosley says Gennady Golovkin vs. Andre Ward is a great megafight for the future
::2014/03/02::
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A.M. Leonard
A.M. Leonard's Tool Story
::2013/09/05::
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Speed control of DC Shunt motor by  Flux control
Speed control of DC Shunt motor by Flux control
::2013/09/13::
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Who control the American military? Who owns their allegience? Who
Who control the American military? Who owns their allegience? Who's order have priority?
::2012/06/21::
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Leonard and Joyce Repass Program A 110 x264
Leonard and Joyce Repass Program A 110 x264
::2013/12/18::
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Mind Control
Mind Control
::2011/03/03::
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Lisa Controller on Gearless Machine - Consult Lifts Training Area
Lisa Controller on Gearless Machine - Consult Lifts Training Area
::2013/04/03::
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WARD
WARD'S COLLECTION: "POSTERS OF WISDOM" OLD
::2013/12/28::
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Micky Ward revisits 9th round of first Gatti Ward bout
Micky Ward revisits 9th round of first Gatti Ward bout
::2013/10/23::
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Floyd Mayweather BASHES Andre Ward in the Boxing Media-1st TakeESPNTV
Floyd Mayweather BASHES Andre Ward in the Boxing Media-1st TakeESPNTV
::2013/11/18::
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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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