Mounting and Connecting the AT180 and V180 Potential Transducer GENERAL COMMENTS The Highland model C740 Potential Transducer is used to interface AC line voltage inputs to the V180/AT180 electrical measurement modules. The C740 is a small (5" x 3.25" x 2") diecast NEMA-4 rated aluminum box having a gasket-sealed top cover and two 7/8" cutout holes, one on each end. Internally, the box is divided into two halves, a "high voltage" input section and a "low voltage" output section. The function of the C740 is to divide-down high-voltage AC line levels to low-voltage AC signals which can be safely connected to an electronic measurement module. The C740 contains four voltage dividers, generally used to divide down the phase A, B, C, and N lines of a polyphase AC system. Each divider can accept up to a 500 volt AC input, measured line-to-line or line-to-ground. ********************************** ******** SAFETY WARNINGS ******* ********************************** THE C740 MUST BE SECURELY GROUNDED. REFER TO THE 'GROUNDING' SECTION. THE C740 SHOULD BE CONNECTED TO CIRCUITS WITH LIMITED FAULT CURRENT CAPABILITY. WHENEVER POSSIBLE, CONNECT TO CIRCUITS WHICH ARE PROTECTED BY LOW-LIMIT CIRCUIT BREAKERS OR HIGH-INTERRUPTING-CAPACITY FUSES. THE LOW-VOLTAGE OUTPUT WIRING MUST BE ISOLATED FROM AC LINE-VOLTAGE CONDUCTORS; SEE THE 'LOW VOLTAGE WIRING' SECTION. DO NOT USE THE C740 TO MEASURE AC CIRCUITS RATED ABOVE 480 VOLTS AC LINE-TO-LINE OR LINE-TO-GROUND. HIGHER VOLTAGE CIRCUITS MUST USE APPROVED POTENTIAL TRANSFORMERS TO REDUCE THE AC VOLTAGE TO SUITABLE LEVELS. DURING OPERATION, THE C740 COVER MUST BE PROPERLY FASTENED. PHYSICAL MOUNTING The C740 may be mounted in any of the following ways : 1. The unit may be bolted to a flat surface. Remove the top cover and note the two through-mounting holes. The unit may be mounted using 8-32 machine screws and nuts, or (if mounted to a wood or similar insulating surface) with "wood bullet"-type screws. 2. The C740 may be mounted to the side of an existing electrical junction or equipment box, using an available 7/8" knockout hole. A standard 7/8" metallic bushing and locknut can be used to secure the C740 to either the outside or inside of the box. If the C740 is mounted INSIDE a bigger box, the mounting bushing must be used to secure the LOW VOLTAGE side of the C740 to the sidewall of the bigger box. In this case, the LOW VOLTAGE wiring of the C740 will feed through the side of the bigger box. If the C740 is to be attached to the OUTSIDE of an equipment or junction box, the HIGH VOLTAGE side of the C740 must be secured to the junction box using the bushing, and the HIGH VOLTAGE wiring will enter the C740 through this bushing. 3. The C740 may be suspended in a rigid conduit run, using suitable conduit fastener bushings. If the C740 is mounted in an outdoor location or is subject to water drips or splashes, the two 7/8" wiring holes must be sealed with suitable fittings to protect against water entry. If conduits are used, insure that any within-conduit condensation will not drip into the C740 enclosure. GROUNDING REQUIREMENTS THE C740 ENCLOSURE MUST BE SECURELY GROUNDED, USING GROUND WIRING AND A GROUND SUITED TO THE TYPE AND FAULT-CURRENT CAPACITY OF THE AC LINE VOLTAGE CIRCUITS BEING MEASURED. USE SUITABLE TEST EQUIPMENT TO CONFIRM GROUND INTEGRITY BEFORE APPLYING AC LINE VOLTAGE INPUTS TO THE C740. Three grounding methods may be used, in conformance with local electrical codes : 1. CONDUIT. Grounding may be accomplished by using suitable 7/8" conduit fittings to secure the C740 to properly grounded conduits. 2. MOUNTING SURFACE . If the mounting surface of the C740 is properly grounded, the C740 may be securely fastened to this surface to achieve grounding, with installation per applicable codes. 3. GROUND WIRE. Two brass-colored grounding screws are provided inside the C740 NEMA-rated metallic enclosure. Run a suitable grounding wire through an inlet bushing and secure it to either screw, in conformance with local electrical codes. This wire must be suited to the fault current capability of the AC circuits connected to the C740. WIRING : HIGH VOLTAGE INPUTS AC voltage inputs to be measured are connected to the screw terminals inside the HIGH VOLTAGE side of the C740. Wiring should be 12 through 18 gage, solid or stranded, insulated for the voltage present and in conformance with local electrical codes. A suitable wire bushing or conduit fitting and cut-through protections must be used. Connect the phase A, B, C, and N (neutral) wires to the marked A, B, C, and N terminals, or wire per the measurement project wiring diagram if appropriate. WIRING : LOW-VOLTAGE OUTPUT The low-voltage output of the C740 should be connected to the C760 termination panel using a 4-conductor cable with overall foil shield and drain wire; the maximum recommended cable run length is 200 feet. A UL-2094 type cable is recommended, such as Alpha 2404C or Belden 8729. Connect the four signal wires to the LA, LB, LC, and LN terminals, and connect the shield wire to the LS terminal. These terminals are located in the LOW VOLTAGE side of the enclosure. Refer to the project wiring diagram for color-code connections. Do not allow the shield lead to touch the chassis of the C740, as this may cause measurement errors. The low-voltage cable must pass through a suitable cable bushing or conduit fitting. ****** CAUTION ****** THE LOW-VOLTAGE CABLE MUST BE ISOLATED FROM ANY AC LINE VOLTAGE CONDUCTORS, IN CONFORMANCE WITH LOCAL ELECTRICAL CODES. THIS CABLE MUST NOT BE ROUTED WITHIN CIRCUIT BREAKER, EQUIPMENT, OR JUNCTION BOXES WHICH CONTAIN AC LINE-VOLTAGE WIRING.