Copyright Goodheart-Willcox Co., Inc. 835 Chapter 24 ∣ Track Steering Systems Caterpillar D7E Electric Drive Dozer The Caterpillar D7E dozer uses electrical current flow to propel the tractor. It has a C9.3 ACERT™ diesel engine to drive an electric generator that produces alternating current (AC). The genera- tor delivers AC current through three high-voltage, high-current wires (conductors) into a power inverter. See Figure 24-29. The power inverter controls the electric output by sending high voltage and high current through six wires to two infinitely variable electric drive motors. The two infinitely variable drive motors deliver power to the drive axle differential assembly. A hydraulic steering motor is installed in the tractor for differential steering. The axles deliver power to a right and left final drive assembly. The D7E tractor, however, is not a hybrid drive even though it is an electric drive. This means that the system does not store or recover high voltage or high current in any type of capacitor or battery. D7E Electric Drive Advantages The electric drive system in the D7E dozer provides machine owners with the following advantages: • An engine designed to operate at speeds within a narrow power band, which extends the life of the engine and enables the tractor to use 20% to 25% less fuel. • Lower operating costs. • Strong straight-ahead dozing capacity and excellent maneuverability in tight spaces (similar to hydrostatic drive and differential- steered dozers). Goodheart-Willcox Publisher Figure 24-29. On this Caterpillar D7E dozer, the power inverter receives high voltage, high current electricity from the generator. The inverter delivers the high voltage, high current electricity through six wires to the two individual electric drive motors that provide power to the machine’s axle assemblies. The tractor’s cab has a hydraulic cylinder that lifts the cab for access to the electric drive components. Input from torque converter Low-range clutch High- range clutch Left reverse clutch Right reverse clutch Left forward clutch Right forward clutch Left low-speed clutch Left high-speed clutch Right high-speed clutch Right low-speed clutch Left steering brake Right steering brake Left bevel gear set Left final drive Right bevel gear set Right final drive Goodheart-Willcox Publisher Figure 24-28. The powertrain of a Case 1150B-E and 1450B track loader and dozer uses countershafts, planetary gear sets, clutches, brakes, bevel gear sets, and final drives to control direction, speed, and steering. Hydraulic cylinder to lift cab Output to two electric motors Input to power inverter