Information on Ward Lenard control system

[Doghandler]

Hi guys,

Was wondering if anyone had any info about the Ward-Lenard system of controlling DC motors and generators. In particular using them in draglines. Have search endlessly on the net and have been unable to find anything valueable. Books, sites, anything. Any help would be appreciated.

Thanks

 

[waross]

How old is the dragline?
Is the control system a true Ward-Lenard system or is the term being used to describe a DC motor control system.
A popular method of controlling a DC motor was to connect the motor armature directly to the generator armarure and leave the motor field energised. The motor speed and direction was controlled by varying the generator excitation. The systems used cascaded exciters, amplidyne control, resistor control, sold state control, and sometimes solid state control of an exciter.
The Ward-Lenard system was one of many similar systems.
yours

 

[davidbeach]

Ward-Leonard (note the 'o') is a manufacturer of motor control products, so you might have something other than what follows. A product of Ward-Leonard that became synonymous with their name is a DC motor controller that is a three machine system. A three-phase AC induction motor is coupled to a DC generator, typically with a separate field. The output of the DC generator is fed into a DC motor. Most of the control is done in the generator field, additional speed through field weakening is done in the motor field.

 

[waross]

Hi davidbeach;
That is my understanding. However I have heard other systems called Ward-Leonard, but although the usage was common at one time it was probably in error.
I worked on some Amplidyne systems many years ago. The smaller systems (40-50 hp.) used static excitation for the motor and amplidyne exitation for the generator. The larger systems (150-200 hp.) Used two conventional exciters, One for the motor and one for the generator. The field of the generator exciter was controlled by an amplidyne.
I understood that the original Ward-Leonard system used resistors to control the generator field. Did they use the resistors to control an exciter field on the larger drives?
respectfully

 

[waross]

Here are some links to Ward-Leonard information.
On comment refers to Ward-Leonard drives as 1900's technology, hence my original question as to the age of the dragline.

http://icosym-nt.cvut.cz/odl/partners/jku/Examples/WardLeonard/Maple/WardLeonard1.html

http://www.porttechnology.org/journals/ed9/download/09.041.pdf

http://www.ewh.ieee.org/soc/pels/AboutPELS/Areas/motors.html

respectfully

 

[Doghandler]

Marvelous gentlemen. Thanks

The draglines are controlled by digital drives (one each for the genrators and the motor fields) but the control used is based on the Ward-Leonard system. The draglines are over 30 years old but obvioulsy the controls are somewhat updated using drives and PLC's.

Once again thanks for all the info and hopefully I can help you guys out when you need.

Tah.

 

[waross]

I worked on a large dragline a little less than 30 years ago. (75-80 Cu. Yd., 320 ft. working radius.)
Main hoist 8 x 1300 Hp., Drag 8 x 1050 Hp.
Each motor was direct connected to its own generator. The motors had constant field excitation.
The Generator field control was solid state. There may have been an exciter between the electronic controls and the generator fields, but I don't remember. 200% Field forcing was also used for fast response. That is, for example, if the operator moved his control to increase the speed from 40% to 50%, the output of the solid state module would go to 200%. When the circuits determined that the speed had reached the intended 50%, the output of the solid state module would drop to maintain that speed level.
If you are trying to follow the control logic, watch for field forcing circuits.
Another issue with draglines is lowering a loaded bucket. If the operator tried to lower a loaded bucket instead of dumping it, the load compensation would act in reverse and accelerate the downward travel. This would increase the current and the circuits would erroneously interpret this as an increased load and increase the field. Field forcing would cut in and the motors would go into runaway, while the loaded bucket free fell.
You may find other logic in the control circuits to avoid this issue.
But hey, isn't there anyone on the forum with more recent experience on draglines?
respectfully

 

[Doghandler]

Where was this dragline? The biggest dragline used to be Big Muskie but now that that is decomissioned the largest is now at Peak Downs mine which is where I just started working.

 

[waross]

As I remember, Big Muskie was a 250 Cu. Yd. machine. Model B&E 250
I worked on B&E #1 at Syncrude. It was a basic 125 Cu. Yd. Machine with extra counterweight and an extended boom (400 Ft.) to get the 360 Ft, working radius. Boom tip was 214 Ft. Elevation. This gave them the capability to stack to a height of about 150 Ft. more or less, but the bucket capacity with the extended radius was about 75 or 80 Cu. Yd.
Respectfully