A GTO powered AC drive system increases the performance of off-highway haul trucks

Existing DC diesel-electric drive systems for off highway haul trucks are at the limits of economical feasibility due to high maintenance costs and power, speed and space constraints of their DC traction motors. Large-scale introduction of AC drives in the rail transportation sector has made compact, powerful, and rugged inverter drives economically viable for the specialty, off-highway hauler market. This paper presents a new AC haul truck drive system featuring GTO inverters, greatly enhanced electric braking, and innovative cooling concepts. A very large increase in electrical power rating allows these trucks to be coupled to overhead trolley lines for an 80% increase in on-grade speed and reduced cycle times. Design features, test results, operational experience, and the outlook for trolley systems are discussed.