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Ward Leonard Motor Control System

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Mechanical Features and Designs

The Ward Leonard motor control system was devised by inventor and engineer, Harry Ward Leonard, in 1891. It has been used in wide variety of devices and equipment even today, with minor improvements or revisions made. Manufacturers for large machinery such as stripping shovels, draglines, and excavators have utilized the Ward Leonard Control system to allow them to be operated by electricity without the fear of burning out.

The Ward Leonard motor control system utilizes AC powered motor generator sets to power DC motors with the motion of the machinery. Mining and construction equipment such as stripping shovels benefited from this invention. It is also used for the operation of many elevators and still remains in use today.

[edit] How it Works

Leonard had patents for more than 100 inventions during his lifetime, but is best known for the Ward Leonard motor control system. The Ward Leonard system was devised in 1891. It involves a prime mover (usually an AC or alternating current motor), which operates a direct current or DC generator at a consistent speed. The framework of the generator is connected to a direct current or DC motor. The motor, in turn, is responsible for adjusting the speed of the equipment and does so by altering the output voltage of the generator with the help of a rheostat. The flow of the motor field typically stays unaltered and can be reduced at times to increase the speed of the base. Ward Leonard systems typically include an exciter generator that is operated by the prime mover in order to field power supply from the DC exciter.[1]

[edit] Equipment and Uses

The Ward Leonard motor control system has been useful for many different concepts and industries. It became of particular use to the developing of steam shovels for manufacturers such as Marion Steam Shovel Co. and Bucyrus Co. Both utilized the Ward-Leonard control system for their steam-powered shovels and excavators because without it, large machines could not get the full power required from electric motors. The Ward Leonard system, using AC powered generator sets to transmit power to DC motors allows maximum pull for the machine’s motor while preventing it from burning out.

The first shovels to utilize this system were the 225-B, produced by Bucyrus, and the 300-E manufactured by Marion. Once it was incorporated into these models, it became the standard configuration for all electric shovels.[2]

[edit] References

  1. Who is Ward Leonard? Ward Leonard. 2008-09-30.
  2. Haddock, Keith. The Earthmover Encyclopedia. Motorbooks: St. Paul, 2003.