Dual alternating current chopper speed regulation of wound-rotor asynchronous motor

Abstract

The invention relates to dual alternating current chopper speed regulation of a wound-rotor asynchronous motor, which belongs to the technical field of electrical engineering. Rotor resistance speed regulation has the disadvantages of large energy loss and difficulty in realization of stepless speed regulation. A speed regulating scheme containing an inverter link has the disadvantages of complex system, low power factor and narrow speed regulating range, and is not suitable for low-power motors. A scheme that a main rotor loop contains a direct current chopper link has the disadvantages of large current capacity and poor reliability of a self turn-off element which is used. Aiming at the problems, the invention provides a new technical scheme, i.e. a dual alternating current chopper is used for chopping slip voltage, so as to change an equivalent value of the slip voltage to realize the stepless speed regulation and achieve the effects of more significant energy saving effect, higher power factor, better starting performance and mechanical properties, wider speed regulating range, small current capacity of the self turn-off element and simple and reliable system. The scheme can be used for large speed ratio stepless speed regulation of the wound-rotor asynchronous motor in various sizes and is especially suitable for the situation that impact load often occurs.

Description

1. Technical field [0001] Electrotechnical 2. Background technology [0002] Compared with the squirrel cage asynchronous motor with the same capacity, the wound asynchronous motor can obtain smaller starting current and larger starting torque, and has the characteristic of adjustable speed. Therefore, although its speed regulation method is not satisfactory, it is still widely used in many sectors of the national economy. [0003] At present, the speed regulation methods of domestic wound asynchronous motors are as follows: [0004] 1. Rotor series resistance speed regulation This speed regulation method is based on the proportional relationship between the critical slip and the reduced resistance of the rotor. During the speed regulation process, the slip energy is consumed on the rotor resistance, so the efficiency is low and the mechanical characteristics are soft. Because it is inconvenient to change the series resistance value through multiple switching, it is diffi...

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Problems solved by technology

[0014] Even this choice cannot guarantee the safety of the components, because the inrush current of ordinary motors when they are directly started, blocked and "overturned" by the inverter is much greater than this

Therefore, there is a potential danger of thermal breakdown of components due to overcurrent protection failure

[0015] Due to the influence of the commutation voltage drop of the rectifier bridge and the limitation of the minimum inverter angle of the inverter, the power factor of this scheme is not high enough, and the minimum speed is not low enough; The process is accompanied by energy loss, and its energy-saving effect is not satisfactory

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