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Speed estimation methods for sensorless induction motor drives can be divided into two groups. One is based on information about fundamental components of stator currents and voltages. The other is based on high-frequency components injection in stator voltages or currents. The latter may operate stably under zero frequency, which occurs in regenerating mode at low speeds. It, however, causes loss increasing and torque ripple. The former is difficult to operate under zero frequency. We propose a stable method categorized in the former group even in regenerating mode at low speeds. The proposed method is based on an adaptive flux observer. First, a new observer gain design is shown. Next, a method avoiding zero-frequency operation with controlling a rotor flux level is proposed. Index Terms--Adaptive observer, induction machine, low speed, regenerating operation, sensorless drive, zero frequency.

Several field-oriented induction motor drive methods without rotational transducers have been proposed. These methods have a disadvantage that the rotor resistance variation causes an estimation error of the motor speed. Therefore, simultaneous estimation of the motor speed and the rotor resistance is required. This paper presents a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing ac components on the field current command. The validity of the proposed method is verified by simulation and experimentation.

The performance of PWM-controlled thyristor rectifier operating at unity fundamental input power factor in PWM current source GTO inverter system for high speed high horse power induction motor drive is analyzed and found out in this paper. With the application of an energy rebound circuit in the dc link of the inverter for PWM control of the thyristor rectifier, a PWM control current source GTO inverter has been proposed. The principles and fundamental behavior of this inverter also have been investigated. A prototype unit of the PWM-controlled current source GTO inverter system is used to drive an 8 pole, 400 Hz, 5.5 kW three-phase induction motor. With the analytical and experimental results, the performance of the dc voltage control of the PWM-controlled thyristor rectifier for various values of the number of pulses for a half period of the supply frequency is also given in detail in this paper.

The purpose of this work is to analyze a steady state performance of inverter-fed high-speed induction motor with trapezoidal rotor bars taking into account crosspath resistance between adjacent rotor bars. The performance of the induction motor drives for various crosspath resistances of two kinds of rotor slot shapes, a rectangular bar and a trapezoidal bar, is discussed on the basis of theoretical and experimental results of a 2.2-kW 500-Hz 15000-rev/min three-phase induction motor. It is also shown that the equivalent rotor resistance and leakage reactance change with crosspath resistance between adjacent rotor bars for various values of the fundamental supply frequency, the rotor slip, and the harmonics. The results of this research will be applied for design consideration of a high-speed induction motor with uninsulated rotor bars.

The effects of crosspath resistance between adjacent rotor bars on steady state performance of inverter-fed high-speed cage induction motors are discussed. It is shown that the equivalent rotor resistance and leakage reactance change with crosspath resistance between adjacent rotor bars for various values of the fundamental supply frequency and the slip. The steady state characteristics of the high-speed induction motor drives for various crosspath resistance are discussed on the basis of theoretical and experimental results. The results of this research will be applied in the design of a high-speed induction motor with uninsulated rotor bars.

This paper presents a new method of estimating the speed of an induction motor. This method is based on adaptive control theory. Experimental results of a direct field-oriented induction motor control without speed sensors are presented.

SUMMARY This paper presents a new position sensorless control system for an interior permanent magnet synchronous motor (IPMSM). The proposed method is based on the extended electromotive force (EMF) and voltage injection synchronized with a pulse-width modulation carrier. The proposed method does not need to switch the estimation method by speed in order to estimate the magnetic pole position by extended EMF, even at low speeds. Further, the amplitude of the superimposing voltage is changed according to the extended EMF; the applied voltage is not saturated in the high-load and high-speed regions. The effectiveness of the proposed sensorless control system was verified experimentally. [ABSTRACT FROM AUTHOR]