Aluminum TMK 40A

ANSI Type A TMK40A Vertical Break Switches (345-765kV)

Type: TMK40A
Orientation: Upright mounting
Ratings: 345kV through 765*kV
Ratings A: 1200, 1600, 2000, 3000* and 4000* Amperes

    TMK 40A
    Vertical Break Switch

    In 1998, Turner Electric acquired the DELTA-STAR High Voltage line, name and product rights. For more than 70 years prior, DELTA STAR switch products were the industry leaders, recognized worldwide for their superior quality and engineering.


    The “TMK40A” vertical break, air break switches described here are based on those designs and tested to meet the requirements of the latest revisions of ANSI & NEMA Standards. It is recognized that, over the past several decades, these switches have undergone design variations intended to meet a different set of criteria, particularly temperature rise requirements. Some system requirements include adherence to earlier standards for the purposes of uniformity of equipment. Whenever possible, every effort will be made to provide switches adhering to those earlier standards.
    DELTA-STAR air break switches have found a home on electrical systems around the world. In recent years, international practice is to use IEC Standards for electrical systems. Our air break switches meet or exceed applicable IEC Standards.

    Design Features

    The DELTA-STAR vertical break, air break switches types “TMK40A” live parts are fabricated from aluminum alloys with tinned copper moving contact interchanges. These switches are designed for upright mounting. In special application, the “TMK40A” switches from 8.25 to 230kV can also be furnished for vertical or underhung mounting.
    Our construction results in a perfectly counterbalanced blade that can be stopped in any intermediate position from fully closed to fully open without danger of the blade failing to the closed position. Having the counter moment always equal to the blade moment provides a low, uniform operating effort.

    Fully Controlled Blade Mechanism

    The fully controlled blade mechanism of the switches is simple in construction and extremely rugged. It consists of three moving parts that keep the blade under positive control during the entire operating cycle. Double rows of stainless steel balls running on machined races are used throughout to assure ease of operation.
    Factory sealing of the entire driving mechanism assures permanent adjustments and eliminates maintenance for the life of the switch.

    High Pressure Contacts

    The switches utilize the same type of contacts at both the hinge and jaw ends. They are of the high-pressure-point design and are fully accessible for easy inspection and maintenance. Contact shoes are of hard-drawn copper with heavy silver inlays, fully tinned after fabrication. Inlays are brazed in position by special equipment that applies heat and pressure simultaneously to assure a permanent high-conductivity bond. Point contact is established at the intersection of the round surface of the blade and silver inlay.
    Contact pressure is provided by stainless steel, multiple leaf springs located outside the current path. Stainless steel bolts and lock washers are used to bolt the contact shoes and springs to the castings.

    Positive Closed Position Lock

    A closed position lock is provided to eliminate blade movement even during severe short circuit conditions. As the blade enters the contact jaws and rotates, the blade edges engage the offset in the contact shoes, locking the blade in position. A positive engagement of the blade and contact shoe offset is accomplished by a disc attached to the contact spreader pin. On opening, the blade is rotated away from the contact shoe offset, leaving the blade free to rise. On switches rated below 46kV this feature is omitted since the shorter blades are sufficiently rigid and will not move under short circuit conditions.


    A complete line of accessories for the switches is available.

    1. Motor operating mechanisms for use with the switches are available in various speeds and torque values. See “Automation and Motor Controls/SF100/200/300”.
    2. Grounding switches for grounding contact and/or hinge end of the switches.
    3. Interrupting devices for interrupting load, line-charging current, transformer magnetizing current and some capacitor switching. See “Vacuum Interrupters”.
    4. Vertical operating shaft auxiliary switches have two (2) to twelve (12) adjustable contacts.
    5. Outriggers and wire guides, both switch-supported and line swivel types.
    6. Mechanical-type interlocks.
    7. Lugs for rigid and stranded bus, including bronze Aluminum, or tinned bronze. Expansion connectors are also available.

    A typical switch includes:

    1. Arcing horn for upright switches up to and including 230kV.
    2. Single-throw operating mechanisms having one offset bearing or two universal joints.
    3. Manual operating mechanisms with standard vertical operating pipe, couplings, guides, levers, clevises and position indicators.
    4. One of the following manual operators:
      1. Torsional swing handle (36′ or 54″ collapsible).
      2. Gear box.
    5. Motor mechanisms, where required in lieu of manual operators.
    6. Flexible grounding braid for grounding the vertical pipe above the handle.
    7. Standard station post insulators as listed in Ordering Information.
    8. Base mounting holes per ANSI C37.32-2.4.4 can be furnished when required.
    9. Standard terminal pad drillings per NEMA CC 1-4.05 are furnished. For special drillings or arrangements please refer to the factory.

    *Refer to factory for details for 500 and 765kV as well as 3000 and 4000 Ampere ratings

    Make Your Vertical Break a Load-Break Switch

    For more than 35 years, Turner Electric’s TECO-Rupter® Vacuum Interrupters have been the technology of choice for loop and load-break applications because of their current-interrupting ability, superior reliability and ease of application.

    The TECO-Rupter offers industry leading performance levels including superior TRV ratings compared to other load-break technologies such as SF6, longer service life and greater interrupting capacity. No other load-break device provides 5,000 full load operations at either 2,000 or 3,000 Ampere ratings and a TRV rating up to 57kV.