Linear Concept Development
Once we decided
on a linear concept development our design strategy focused on five key
A. Track Systems
Two basic track systems were
given the most consideration: rack
and pinion and screw-based, or ball-screw, system. The ball-screw
system presented the best accuracy over range of motion, with very high
Fig. B1. Rack and pinion
Fig. B2. Ball screw linear rail with
stepper motor attachment.
B. Carriage System
Design of the
was centered around a concept called a resistor bridge. In order to
perform its function properly, our tap changer was
required to maintain contact with the previous row of contacts before
the tap transition to the next row was complete. This
"make-before-break" requirement resulted in a resistor
bridge being the central component of our carriage design. The planned
resistor bridge calls for three brushes in a parallel
configuration, connected to resistors; three of these bridges will sit
side-by-side in the center of the carriage assembly. With subsequent
designs we modified the
carriage to use a material other than metal (such as acrylic board) to
support the resistor bridge.
Fig. C1. Resistor
bridge concept for achieving make-before-break.
Figs. C2 and C3. Drawing
of a carriage
assembly, incorporating the resistor bridge concept, for use with
either rack and pinion or ball screw track
Drawing of carriage assembly (from Figures D2 and D3) traveling
over contact surface.
Figs. C5 and C6. Testing the
mechanical motion of the prototype resistor bridge over a series of
contacts. Fig. C7 (far right).
Close up of resistor bridge prototype.
Figs. C8 and C9. Prototype with
resistor mounted on platorm (left) and being tested in the ECE lab in
Figs. C10,C11,C12. Revised
of carriage mated to a Haydon Kerk LRS (top), and carriage views from
front, or direction of travel (bottom left) and from the side (bottom
C13. Present carriage
design from angle with nine carbon
brushes and six resistors. The
resistor stacks on either side of
the bridge face the direction of
C. Contact Surface
Fig. D1. Contact
surfaces for the above carriage design will utilize carbon brushes
traveling over copper contacts.
Final Concept Design
Selected Concept (no final decision as of yet)
Fig. E1. Present concept design for
phase-shifting transformer tap changer, integrated with a Haydon-Kerk
LRS. The triangular structures on either end of the device are intended
the tap changer as it moves from one tap to the next.
Fig. E2. To provide a
sense of scale, the proposed tap changer design is
shown mounted on a cart. The transformers would rest on the lower