Location History:
- Manchester, EN (1978)
- Droylsden, GB (1984)
Company Filing History:
Years Active: 1978-1984
Title: Innovations by John David Markham
Introduction
John David Markham is a notable inventor based in Manchester, GB. He has made significant contributions to the field of electrical engineering, particularly in the area of dynamic braking systems for direct current motors. With a total of two patents to his name, Markham's work showcases his expertise and innovative thinking.
Latest Patents
Markham's latest patents include a dynamic braking system for D.C. traction motors. This system utilizes an asymmetric bridge rectifier with freewheel diodes, allowing for the circulation of motor-generated current. The innovative design employs field reversal to ensure that the generated braking current direction aligns with motoring. This capability enables injection current braking by phasing up the supply bridges during braking with full excitation. The brake resistance is divided into two parts, one of which forms an uncontrolled arm of the bridge, shunted by a thyristor. This design results in lower losses and greater braking efficiency.
Another of his patents focuses on a braking system for separately excited D.C. traction motors. In this system, rheostatic braking is achieved through field reversal, generating armature current that freewheels through a low impedance supply and a brake resistor in series with the armature. A contactor shorts out the brake resistor during normal motoring. The system detects field excitation in conjunction with armature current or voltage polarity reversal, indicating the motor's generating function. This prevents short-circuiting of the motor/generator, allowing for safe plug braking through energization of the armature supply.
Career Highlights
Markham is associated with Associated Electrical Industries Limited, where he has applied his innovative ideas to develop advanced electrical systems. His work has contributed to enhancing the efficiency and safety of traction motors, making a significant impact in the industry.
Collaborations
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Conclusion
John David Markham's contributions to the field of electrical engineering, particularly in dynamic braking systems, highlight his innovative spirit and technical expertise. His patents reflect a commitment to improving the efficiency and functionality of direct current motors.