Concept Development

labwork


PSTTC Design Configuration Options


Our team explored a range of configurations for the new tap changer: linear, rolling pin, knife blade, and record player. Ultimately, we settled on the linear system for its simplicity, functionality, and ease of operation.

Three views prototypes
Figs. A1,A2, and A3. Rolling tap (left), knife-blade (center) and record player configurations.

MBB View  
Fig. A4. Linear Track System.

Linear Concept Development

Once we decided on a linear concept development our design strategy focused on five key areas:

  • Track system
  • Carriage system
  • Contact surface
  • Driver mechanism
  • Control system


  • 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 speed.

    rackpinion
    Fig. B1. Rack and pinion system.

    ballscrewlrs
    Fig. B2. Ball screw linear rail with stepper motor attachment.


    B. Carriage System

    Design  of the carriage system 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.

    bridge
    Fig. C1.
    Resistor bridge concept for achieving make-before-break.

    doublepic
    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 system.


    contact
    Fig. C4.  Drawing of carriage assembly (from Figures D2 and D3) traveling over contact surface.


    carriageprototypeconstruction
    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. 
     

    testingprototype
    Figs. C8 and C9. Prototype with resistor mounted on platorm (left) and being tested in the ECE lab in BEL 


    carriage3view
    Figs. C10,C11,C12. Revised views of carriage mated to a Haydon Kerk LRS (top), and carriage views from the front, or direction of travel (bottom left) and from the side (bottom right).

    carriageangle
    Fig. 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 travel.


    C. Contact Surface


    contact
    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)

    tapchangersideview

    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 to help stabilize the tap changer as it moves from one tap to the next.

    tapchangeroncart
    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 shelf.