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The Ward Leonard motor control system

The Ward Leonard motor control system was H.Ward Leonard’s best known and most lasting invention. It was introduced in about 1891 and became the most widely used type of electric motor speed control.

The Ward Leonard system, a prime mover drives a direct current (DC) generator at a constant speed. The armature of the DC generator is connected directly to the armature of a DC motor. The DC motor drives the load equipment at an adjustable speed. The motor speed is adjusted by adjusting the output voltage of the generator using a rheostat to adjust the excitation current in the field winding. The motor field current is usually not adjusted, but the motor field is sometimes reduced to increase the speed above the base speed. The prime mover is usually an alternating current (AC) motor, but a DC motor or an engine might be used instead. To provide the DC field excitation power supply, Ward Leonard systems usually include an exciter generator that is driven by the prime mover.

Although only technical specialists are likely to be familiar with Ward Leonard systems, many millions of people have ridden in elevators powered by Ward Leonard drives. From the 1920’s through the 1980’s most electrically driven elevators used Ward Leonard control and many systems remained in use at the beginning of the 21st century.

Many variations of the Ward Leonard system have been implemented, but they have generally continued to be called Ward Leonard systems. H. Ward Leonard and many others have patented auxiliary control systems used to regulate the motor speed as required to automatically perform specific tasks such as controlling pump speed to regulate flow.

Mechanical types of adjustable-speed drives and other electrical types continued to be used and new types developed after the Ward Leonard system was introduced. Electron tube types of DC motor controls began to be developed in the 1920’s but electronic controls didn’t seriously begin to displace the Ward Leonard system until Thyristor controlled drives were developed in the late 1960’s. By the mid 1970’s, Ward Leonard drives were rapidly becoming obsolete, but the replacement of existing Ward Leonard drives has continued past the end of the 20th century. I’m sure even now there is still some similar working out there. I wonder if the same will happen with modern inverters and drives.

NOTE: Our company HWL is in no way associated with H.Ward Leonard or his systems. But we think he is one of the forgotten engineers who were of brilliance in his field at the time.

HWL is an independent company Based in the County town of Stafford. We specialize with motion control mainly our field is inverters and the later year’s motors. We however have diversified to Kitchen Fume extraction which is still a form of motion control. We have a small team of Engineers and in September 2012 we will be taking on a new role of design engineer. This will be a new part of HWL and we are offering a new design service where we can take your old drawing and put them onto new software and also where there are no good drawings though reverse Engineering are able to reproduce them.

HWL was formed in 2008 just as the Banks crashed and the rescission took hold. This didn’t bother us as we wanted our company to work and though hard work and paying attention to customer service we have steadily grown over the past few years.

Formerly trained at Control Techniques who let me do my final years at University after been out of education since joining the Royal Air force where I was an Air Radar Technician.

Together with my team we aim to grow by 35% each year and the launching of our new web site with on line sales in August 2012 should help us grown to reach our goals.

We are always willing to talk to manufactures that either require our services or would like us to be there agents and market their products.

Where did the name of HWL Technical Solutions come from?

We would like to tell you a bit about how we came across the name of HWL Technical Solutions. Whilst studying Engineering at University I was very interested in Inverters, Power and Motion Control and the name Harry Ward Leonard kept coming up. Since this Engineer was in the forefront of inventing control and automation it would only be right to name a company after this great man.

Harry Ward Leonard was an electrical engineer and inventor whose 30-year career spanned the late 1800’s and the early 1900’s. He is best known for his invention, the Ward Leonard motor control system. Equipment based on his invention remained in service into the late 1980’s.