Control Of Squirrel Cage Induction Motor Research Articles

Investigation of energy parameters of a compensated asynchronous motor in the mode of repeated short-term starts

The study is devoted to energy efficiency control of squirrel-cage induction motors of low and medium power and is a continuation of development of the theory of compensated induction motors. The aim of the research is to substantiate the influence of capacitance value on compensation of internal capacitive reactive power of induction motor in starting mode. The mathematical modeling of compensated induction motor allowed us to study quasitransient electromagnetic processes taking into account spatial and temporal directionality of currents of main and additional windings of stator and rotor phases of compensated induction motor. Achievement of the objective is based on the establishment of regularities of influence of compensating capacitance value on energy characteristics of a compensated induction motor during its start-up and achievement of nominal electromagnetic torque on the rotor shaft. Numerical modeling is performed at spatial displacement of phase axes of main and additional phase windings of stator of compensated induction motor by 30°. It provides equality of currents of main and auxiliary stator windings of CAM. As shown by numerical experiment, changing the value of compensation capacitance gives an idea of the conditions for ensuring normal excitation mode of such electrical device. Provision of normal excitation at start-up of a compensated induction motor leads to changes in energy parameters of the machine - minimization of power losses in windings and reactive power consumed by the motor and increase of its power factor. It has been established that the value of compensation capacitance required to ensure normal excitation mode at start-up and steady-state normal mode of a compensated induction motor is different. As a result of simulation, it was found that to ensure energy-efficient starting mode and acceleration to nominal slip, the value of compensating capacity of induction motor should be almost 5 times greater than for the steady-state nominal mode. The results of these studies can be useful for improving the energy efficiency of microgrids with small and medium capacity induction motors.

Inverter design for efficient variable-speed drives

The application of power electronics to the control of squirrel-cage induction motors has led to an improvement of efficiency of many industrial processes, if not the motors themselves. Here we examine the range of electronics available for this control equipment.

Electronic Analog Slip Calculator for Induction Motor Drives

For some schemes of variable speed control of squirrel-cage induction motor fed by a current-source inverter, accurate evaluation of motor slip frequency is essential for obtaining optimum torque output. For evaluating slip accurately, a digital speed transducer coupled to the shaft is generally required. Such a transducer and the associated digital circuits make the system complex and expensive. An analog speed transducer which is relatively cheap could be used only if the slip could be obtained accurately by some other means. This paper presents an inexpensive and accurate method of obtaining an analog signal proportional to the slip by using a simple calculator circuit that uses the dc link current, dc link voltage, and inverter frequency as its inputs. The slip calculator described here is capable of giving the correct output only under steady-state conditions. The design of the slip calculator is illustrated in the Appendix with the aid of a numerical example.

Speed control of squirrel-cage induction motor

Speed control of squirrel-cage induction motor