Talk:Ward Leonard control

Article needs work

This article needs work. For a better explanation of a Ward Leonard drive, see [1] --John Nagle (talk) 19:11, 19 November 2007 (UTC)

Seconded. I still don't get it. Wizzy…☎ 16:10, 15 July 2010 (UTC)

not clear

if the purpose of the primary generator is to eliminate a starter, constant DG driving a variable current motor, how does one eliminate the starter in the second motor? I do not think Ward Leonard is as simple as it has been put here. The purpose is the AC to DC because speed control in DC is better -Alok 21:34, 10 February 2013 (UTC) — Preceding unsigned comment added by Alokdube (talk • contribs)

Basic concept -v- Technical description.

The basic concept section consists of eight paragraphs. The more technical description section has just four short sentences. Summat is wrong here. DieSwartzPunkt (talk) 18:25, 4 February 2014 (UTC)

You have a point. Most of the content in the "basic concept" section after the first paragraph could be deleted. It's uncited obscure technical detail. --John Nagle (talk) 19:12, 4 February 2014 (UTC)

I now have a problem with your rewrite. Your rewrite is suggesting that Ward Leonard control applies solely to the use of the dynamo as an amplifier with its use to drive a motor as a possible application. While that was certainly how the dynamo was used, the Ward Leonard control scheme specifically includes the driven motor (or motors in very large schemes) as part af the scheme. There was nothing much wrong with the original section but I felt that it belonged in the next section (though some of it was dubious or open to challenge). References are still easy to find (e.g. a very good thesis on the subject [2] dodgy grammar and details in places presumably because it is a translation - the concept of motor brushes made from coal is a novel idea!). This thesis also underlines the fact that the driving motor does not have to be a constant speed device such as three phase induction motor or even electric. Although not specifically refered to as such, the electrical part of diesel electric railway locomotives is still a Ward Leonard system. DieSwartzPunkt (talk) 14:08, 5 February 2014 (UTC)

That thesis is a fun read, but it's just a student's report. The early Heilmann steam-driven locomotive mentioned, with Ward-Leonard drive, is interesting. See Heilmann locomotive for a full article. While a few Diesel-electric locomotives used Ward-Leonard drives, most don't use the generator that way. Here's a classic EMD schematic.[3]. The generator field is adjusted to keep the engine load constant, not as speed adjustment. The transition controller connects the motors in various combinations of series and parallel. Speed is controlled with a combination of engine throttle and transition setting. See Diesel locomotive#Diesel-electric; the section on propulsion control discusses why a Ward-Leonard system is not used. There's a nice one-page summary of the Ward-Leonard system here.[4] Drawing a diagram like that would be helpful. (The diagram, though, assumes the system power input is DC; for most elevators, the input is AC and the first motor is an AC motor.) As for the final motor being part of the Ward-Leonard system, it has to be analyzed as part of the system for design purposes, but it's really just an ordinary DC motor with a variable voltage input. John Nagle (talk) 18:33, 5 February 2014 (UTC)

Railway traction is not my speciality, but I do remember diesel-electric raiway traction being mentioned in my student days as an application. As ever, time moves on and better ways of doing the same thing are inevitably found. In my later lecturing days, one of the practical exercises that my students had to perform was to create a Ward Leonard system in the lab and analyse it. It was created with a DC driving motor, but only because the machinery that was matched closely enough were two DC motor/DC generator sets (the second generator acted as the mechanical load on the 'output' motor). Our 3 phase motor/DC generator had too small a rating. Due to the complex nature of the analysis, this practical exercise was one of two that were conducted as a class exercise rather than in groups of three (the other being the Hopkinson test). It was always interesting to see the different ways in which classes would organise themselves to carry out the task - some vastly more efficient than others. It was dropped from the sylabus after I had been teaching it for just two years. DieSwartzPunkt (talk) 12:54, 12 February 2014 (UTC)