STARTING TORQUE AND MECHANICAL CHARACTERISTICS OF AN ASYNCHRONOUS MOTOR FOR A GEARLESS DRAW BENCH
This paper analyzes an asynchronous motor for electric drives used in geared n-block draw benches for making steel wires from hot-rolled billets (8 to 12 mm in diameter). Modern draw benches are shown to feature adjustable automated electric drives based on conventional asynchronous motors, frequency converters or soft starters. The paper describes the primary features of the drawing process and the most important requirements to the draw-bench electric drives; one such requirement is a specific starting torque. It is noted that the shaft of the asynchronous motor, the starting torque of which is 1.6 to 2.2 times as large as the nominal torque, transmits its torque to the shaft of the intermediate block via a reduction gear that reduces the speed but multiplies the torque by 3.5 to 16.5 times. Using such reduction gear lowers the electric drive efficiency by at least 13 to 20 %, making the drawing process less energy-efficient and the final product less competitive. The objective here is to study the asynchronous motor torque to design a gearless draw bench and elective drive based on an object-oriented asynchronous motor with a greater starting-torque multiplicity. The proposed solution to the problem takes into account the saturation of the motor magnetic system and the current displacement in the rotor winding. The problem is solved by calculus and modeling the mechanical characteristics of the motor in a specialized computer program. It is proven possible to design an asynchronous motor with a starting torque sufficient for gearless drawing. Using a gearless intermediate block will simplify the design and improve reliability while also reducing the operating costs and the power consumption of drawing by 17 to 20 %. The results of the study will be of interest to specialists in electric machines, engineers of electromachine-building enterprises, technologists and designers of mechanical machinery for metalworks.