By Jay Zacharias
We had a problem where the primary step-down transformer from 408 to 120 burned up at our TV transmitter site after having had the site rewired by an electrical contractor to a new power line feed. Everything had worked fine for about 6 months, then the transformer burned up. Investigation using the Fluke DVM and clamp-on AC current meter probe revealed that the contractor didn't balance the load properly between the legs of the power lines. A failure in the tower lighting flasher system caused the tower lights to fail to an "always on" condition, causing a continuous current draw that the contractor hadn't taken into consideration when they switched over to the new power lines. By using the Fluke clamp-on current meter, we were able to determine where the excess current draw was coming from, allowing us to re-distribute the load so that the loads were balanced regardless of the mode of operation.