| In this paper the design and structure characteristics of variable-frequency adjustable-speed three-phase induction motors are introduced. During the design process some unfavorable influence on the performance of motor is fully considered such as higher harmonic in the output voltage and current caused by inverter. The influences on rated current, power factor, loss and efficiency are included. Then the extent of such influences is calculated by means of experiments. Meanwhile the difference of temperature rise between variable-frequency motors and conventional motors is obtained through experiments. The difference of voltage stress generated by inverter supply and fundamental frequency supply is also obtained through experiments. All of these provide solid basis for engineering design of variable--frequency adjustable-speed three-phase induction motors.At present, the primary driving motors of main rolling machines, curling machines and decoilers in steel & iron industries are mostly variable-frequency adjustable-speed motors. Correspondingly the qualifications of these motors are much stricter. In this paper, we analyzed the electromagnetic and structure design characteristics of a 750kW low-voltage variable-frequency motor. During this process problems such as how to select the rated points and how to select parameters of the motor in order to meet the requirements of mechanical load are introduced in detail. All of these give references to engineering design of low-voltage high-output variable-frequency motor. |
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