McGraw-Edison 550C Main Stationary

Overview

stationary contact assembly for the McGraw-Edison 550C load tap changer. Machined to OEM specification or reverse-engineered when the part is discontinued. Material certification available on request.

About the McGraw-Edison 550

The McGraw-Edison 550 is a diverter-switch type load tap changer and one of the most widely deployed LTCs in utility power transformers across North America. Unlike reactor-type designs, the 550 interrupts load current directly at the diverter switch contacts while the selector switch pre-selects the next tap position off-load. The main moving contact, stationary contact, and reversing switch contacts bear the interrupting duty on every tap change. At 100,000 operations or the manufacturer's recommended inspection interval, contact condition directly determines whether the tap changer will perform reliably between outages. The 550B and 550C are higher-current variants with the same general architecture; the BLS and CS suffixes denote connector styles.

Why replace worn LTC contacts

Worn or burned tap-changer contacts raise resistance, run hot, and can lead to tap-changer failure. Precision replacements restore reliable switching and extend the service life of the LTC.

Stock, lead time & reverse engineering

Common items are produced on short lead times; discontinued or hard-to-find parts are reverse-engineered from a sample, a drawing, or a model number. Based in Palm Harbor, FL, Southern Switch & Contacts manufactures and ships replacement parts to utilities nationwide, and has served the industry since 1982.