Electric Drive of an Industrial Tractor 2013-01-2469
A traction electric drive is offered for an industrial tractor. The drive contains the generator, the controlled rectifier, the independent inverters, and two onboard motors. The important feature of the offered electric drive is application of synchronous reactive machines of independent excitation as the generator and traction motors. These electric machines have the following technical features: the generator and motor design is brushless; and simple, the rotor has high mechanical rigidity that raises reliability at high speeds and overloads. There are no windings on the rotor; the motor is designed for ease of manufacture (by expert estimations its price is lower than the squirrel cage induction motor on the order of 15-20 %). The machines have increased efficiency a result of a “cold” rotor design; the motors have high torque overloads capacity (up to 4-6 times the values of nominal torque). The windings of the motor and the generator are single-layered with full step capability of current and voltage. The motor control is transistors based. The range of the torque regulation is 1:10 resulting in constant power for the drive. The stator circuits are supplied from individual current sources via transistor single-phase autonomous inverters. The intermediate direct current link design of the three-wire circuit allows the use of half the number of transistors in the autonomous inverters. In the generator, working and excitation are divided to simplify the power circuits of the converter. The control system of the drive is similar to electric drives of a direct current machine and can have several operating modes. This electric drive is not only a good traction drive, but also has possible application for other mechanisms where high load duty cycles are required for operation, because the simplicity of a design. It is brushless and has a high operational and overload torques capability.