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Ward Leonard - Excellence in Motor & Control Solutions
Ward Leonard - Excellence in Motor & Control Solutions
DATE: 2014/01/23::
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15112012034 grupo ward leonard
15112012034 grupo ward leonard
DATE: 2013/02/06::
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Ward Leonard 01
Ward Leonard 01
DATE: 2011/04/07::
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Lecture - 16 Dc Motor Speed Control - Introduction
Lecture - 16 Dc Motor Speed Control - Introduction
DATE: 2008/04/17::
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Ward Leonard Varistat Dimmer
Ward Leonard Varistat Dimmer
DATE: 2012/06/15::
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Aufzug Antrieb  Ward Leonard
Aufzug Antrieb Ward Leonard
DATE: 2013/11/11::
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High Power Density AC Drilling Motors from Ward Leonard
High Power Density AC Drilling Motors from Ward Leonard
DATE: 2015/05/18::
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Ward Leonard - Allons Enfants - Rock
Ward Leonard - Allons Enfants - Rock
DATE: 2012/02/28::
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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 !!!
DATE: 2011/01/01::
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Conexion Ward leonard... sencillamente explicado
Conexion Ward leonard... sencillamente explicado
DATE: 2013/07/17::
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Ward Leonard 2,000 HP AC Induction Motor Video
Ward Leonard 2,000 HP AC Induction Motor Video
DATE: 2014/05/05::
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Lec-6 DC Motor Speed Control
Lec-6 DC Motor Speed Control
DATE: 2008/08/25::
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Schindler Ward Leonard gearless machines with Aconic controllers
Schindler Ward Leonard gearless machines with Aconic controllers
DATE: 2011/01/13::
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Ward Leonard 02
Ward Leonard 02
DATE: 2011/04/07::
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Ward Churchill Interview on Leonard Peltier
Ward Churchill Interview on Leonard Peltier
DATE: 2012/06/24::
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Dicky Eklund ward steps over  Sugar Ray Leonard the fighter real !!!
Dicky Eklund ward steps over Sugar Ray Leonard the fighter real !!!
DATE: 2011/01/03::
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Leonard Ward - Quit Smoking
Leonard Ward - Quit Smoking
DATE: 2010/05/26::
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Ward Léonard : Présentation + Intro + Les Costards (Live Montereau Confluence 2012)
Ward Léonard : Présentation + Intro + Les Costards (Live Montereau Confluence 2012)
DATE: 2012/06/10::
19
Sugar Ray Leonard Vs Floyd Mayweather Sr 1978
Sugar Ray Leonard Vs Floyd Mayweather Sr 1978
DATE: 2013/12/15::
20
Funicular Mountain Tram Elevator in Prague of Europe
Funicular Mountain Tram Elevator in Prague of Europe
DATE: 2014/01/14::
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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?
DATE: 2012/06/20::
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SUGAR RAY LEONARD  ✰ HIGHLIGHTS BOXING
SUGAR RAY LEONARD ✰ HIGHLIGHTS BOXING
DATE: 2015/06/28::
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Sugar Ray Leonard vs Thomas Hearns — September 16, 1981 [Full Fight]
Sugar Ray Leonard vs Thomas Hearns — September 16, 1981 [Full Fight]
DATE: 2013/02/19::
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Dr.Leonard Coldwell [ Natural Cancer Cures ]LNM 2012
Dr.Leonard Coldwell [ Natural Cancer Cures ]LNM 2012
DATE: 2012/10/03::
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Arturo Gatti vs Micky Ward I HD
Arturo Gatti vs Micky Ward I HD
DATE: 2013/05/27::
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MAYWEATHER SR ON GOLOVKIN BEING NEXT AND WARD VS GOLOVKIN
MAYWEATHER SR ON GOLOVKIN BEING NEXT AND WARD VS GOLOVKIN
DATE: 2015/05/28::
27
TOP SIDE CONTROL Baseball Bat Choke Samurai Choke with Matt Andrews
TOP SIDE CONTROL Baseball Bat Choke Samurai Choke with Matt Andrews
DATE: 2014/04/03::
28
Andre "SOG" Ward vs Mikkel Kessler - Film Study
Andre "SOG" Ward vs Mikkel Kessler - Film Study
DATE: 2015/01/14::
29
Arturo Gatti vs Micky Ward II HD
Arturo Gatti vs Micky Ward II HD
DATE: 2013/07/17::
30
Side Control Escape Far Side Arm Isolated
Side Control Escape Far Side Arm Isolated
DATE: 2014/04/03::
31
MASS SHOOTINGS: At Least 19 Injured In New Orleans Mother
MASS SHOOTINGS: At Least 19 Injured In New Orleans Mother's Day Shooting In America!
DATE: 2013/05/12::
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Review - Unstoppable
Review - Unstoppable
DATE: 2010/11/14::
33
FLOYD MAYWEATHER JR: "PACQUIAO THROWING A LOT WON
FLOYD MAYWEATHER JR: "PACQUIAO THROWING A LOT WON'T WORK AGAINST ME"
DATE: 2015/04/12::
34
Google Free Traffic MLM
Google Free Traffic MLM
DATE: 2009/11/29::
35
Fifty Shades Darker Finds Screenwriter - EL James Hires Husband
Fifty Shades Darker Finds Screenwriter - EL James Hires Husband
DATE: 2015/04/23::
36
Sugar Ray Leonard On Adrien Broner vs Shawn Porter & Thurman vs Mayweather - esnews
Sugar Ray Leonard On Adrien Broner vs Shawn Porter & Thurman vs Mayweather - esnews
DATE: 2015/05/14::
37
The Fabulous Four (Boxing Documentary)
The Fabulous Four (Boxing Documentary)
DATE: 2012/01/18::
38
LEONARD ELLERBE TALKS MAYWEATHER VS. PACQUIAO, REMATCH, PACQUIAO
LEONARD ELLERBE TALKS MAYWEATHER VS. PACQUIAO, REMATCH, PACQUIAO'S INJURY "EXCUSE" AND MORE
DATE: 2015/06/10::
39
Motor Generator 50 cycle ( Hertz in today
Motor Generator 50 cycle ( Hertz in today's lingo )
DATE: 2015/06/29::
40
Arturo Gatti vs Micky Ward I (Highlights)
Arturo Gatti vs Micky Ward I (Highlights)
DATE: 2015/03/14::
41
Boxing Tribute - Marvin Hagler vs Sugar Ray Leonard
Boxing Tribute - Marvin Hagler vs Sugar Ray Leonard
DATE: 2008/01/31::
42
Megyn Kelly Takes On Ward Churchill: How Can You Compare 9/11 Victims to Nazis?
Megyn Kelly Takes On Ward Churchill: How Can You Compare 9/11 Victims to Nazis?
DATE: 2014/09/09::
43
Fights of the Decade: Gatti vs. Ward III (HBO Boxing)
Fights of the Decade: Gatti vs. Ward III (HBO Boxing)
DATE: 2010/02/09::
44
Arturo Gatti vs Micky Ward Highlights (Trilogy)
Arturo Gatti vs Micky Ward Highlights (Trilogy)
DATE: 2012/08/07::
45
Meyers Leonard Drafted 11th by Portland
Meyers Leonard Drafted 11th by Portland
DATE: 2012/06/29::
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BluesTune: Mark Leonard & Bill Champlin, Bruce Gaitsch, B. Ward
BluesTune: Mark Leonard & Bill Champlin, Bruce Gaitsch, B. Ward
DATE: 2011/04/16::
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Gatti v Ward 1 Round 9
Gatti v Ward 1 Round 9
DATE: 2008/06/10::
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Micky Ward vs. Shea Neary - Final Round
Micky Ward vs. Shea Neary - Final Round
DATE: 2011/03/28::
49
Amy Goodman Interviews Leonard Peltier From Prison
Amy Goodman Interviews Leonard Peltier From Prison
DATE: 2012/12/19::
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BOXING Micky Ward VS Alfonso Sanchez Round 7
BOXING Micky Ward VS Alfonso Sanchez Round 7
DATE: 2010/12/04::
NEXT >>
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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