The GE LR65 and LRT65 are load tap changers manufactured by General Electric. The LR65 is used in GE voltage regulators; the LRT65 is the equivalent unit for GE power transformers. Both share the same fundamental transfer switch design but the mounting configuration and some contact dimensions differ between the regulator and transformer applications. Both are available in standard and high-ampere configurations — the high-amp variant uses larger contact assemblies rated for higher continuous current, and high-amp contacts will not install correctly in a standard-rated unit.
The LR65/LRT65 transfer switch uses an arcing contact that absorbs the arc energy on each tap change operation, and a contact finger assembly that carries load current after the arcing contact makes the circuit. This two-element design concentrates arcing wear at the arcing contact tip rather than distributing it across the full transfer switch stationary surface. The result is a predictable, inspectable wear pattern: the arcing contact tip erodes with each operation, and when it reaches the end-of-life limit, it is replaced — the stationary contact surface itself sees relatively little wear as long as the arcing contact is maintained.
The transfer switch stationary contact and the contact finger assembly carry load current in the dwell position between operations. These components develop contact resistance from oxidation and surface roughness but do not see significant arcing wear if the arcing contact is properly maintained. Elevated contact resistance at the transfer switch position despite a serviceable arcing contact points to the stationary or finger assembly.
The arcing contact is the primary wear indicator on the LR65/LRT65. Inspect the arcing contact tip for erosion depth and compare to the manufacturer’s minimum remaining material specification. A contact that has worn to the wear limit must be replaced before the unit is returned to service. Continuing to operate with an arcing contact past its wear limit shifts arcing energy to the surrounding contact surfaces and produces damage that requires more extensive replacement at the next maintenance interval.
The arcing block is mounted adjacent to the transfer switch contacts and absorbs arc energy and carbon deposits during interruption. Inspect the arcing block for carbon buildup, cracking, and evidence of erosion at the arc impingement zone. A heavily carbonized arcing block reduces the arc-quenching effectiveness of the oil and contributes to carbon contamination of the LTC oil compartment. Replace arcing blocks that are cracked or have eroded to the point where the arc impingement zone is compromised.
The selector switch consists of a contact finger assembly that sweeps across outer stationary contacts at each tap position. Inspect selector switch contact finger assemblies for wear at the contact tips and verify that finger pressure against the stationary contacts is adequate. The outer stationary contacts on the selector switch carry full load current at each tap position — inspect each for surface condition, oxidation, and any evidence of overheating at the finger engagement zone. Measure contact resistance at each selector switch position and flag any position showing elevated resistance compared to adjacent tap positions.
The reversing switch on the LR65/LRT65 uses a moving contact assembly that engages left-hand, right-hand, and neutral stationary contacts in the three reversing switch positions. Inspect the moving contact assembly for contact surface wear. Inspect each of the three stationary contacts — LH, RH, and neutral — for pitting and surface condition at the engagement zone. The neutral stationary contact carries current in the neutral tap position and does not see arcing duty, but develops resistance from oxidation over time. Verify that the reversing switch drive positions the moving contact fully in all three positions, with no mechanical binding in the drive linkage.
The LR65 and LRT65 are available in standard and high-ampere ratings. The high-amp contact assemblies use larger contact cross-sections to handle the higher continuous current. Before ordering replacement contacts, confirm whether the unit is standard or high-amp rated from the LTC nameplate. High-amp contacts installed in a standard-rated unit will not seat correctly; standard contacts installed in a high-amp unit will be undersized for the continuous current and will overheat. Both kit and individual contact assemblies are available for each rating.
Southern Switch stocks LR65 and LRT65 contact components in both standard and high-amp configurations. Confirm the rating from your LTC nameplate before ordering.