were used for study. Keywords: Condition monitoring, rotor fault diagnosis, motor current signature analysis, air-gap torque spectrum, air-gap torque estimation.
tor. Through a comparative study using a detailed machine model and the standard dq model, the paper shows that the characteristic frequencies generated by a particular fault are preserved even if the standard dq model is used for estimation of air-gap torque. This is validated through a practical hardware implementation for online spectrum estimation of air-gap torque using TMS320C31, where several faulted cage rotors were used for study. Keywords: Condition monitoring, rotor fault diagnosis, motor current signature analysis, air-gap torque spectrum, air-gap torque estimation. Preprint Order Number: PE-016EC (04-2002) Discussion Deadline: September 2002
A Review of RFO Induction Motor Parameter Estimation Techniques Toliyat, H.A.; Levi, E.; Raina, M. Author Affiliation: Texas A&M University, College Station, TX; Liverpool John Moores University, Liverpool, U.K. Abstract: An induction motor is the most frequently used electric machine in high-performance drive applications. Control schemes of such drives require an exact knowledge of at least some of the induction motor parameters. Any mismatch between the parameter values used
mode. In this paper, conducting screens are incorporated in the rotor of a prototype 400 W, 7500 rpm two-phase switched reluctance machine. The effect of the conducting screens on current response, output torque, output power, and efficiency of the machine are experimentally evaluated and explained. The conducting screens improve the torque at higher speeds, increase the output power, and improve drive efficiency. At low speeds, the conducting screens improve rate of change of inductance and, hence, torque. At high speeds, enhancements of performance are due to a lowered unaligned inductance that provides an improved initial current response. At rotor speeds greater than base speed and below a breakpoint speed, it is found that the conducting screens are detrimental to the performance of the machine. A reason for this phenomenon is given. Keywords: Reluctance motors, variable speed drives, motor drives. Preprint Order Number: PE-084EC (04-2002) Discussion Deadline: September 2002
Analysis and Design of Synchronous Permanent Magnet Planar Motors
within the controller and actual parameter values in the motor leads to a deterioration in the drive performance. Numerous methods for induction machine on-line and off-line parameter estimation have been developed exclusively for application in high-performance drives. This paper aims at providing a review of the major techniques used for the induction motor parameter estimation. The paper is illustrated throughout with experimental and simulation examples related to various parameter estimation techniques. Keywords: Induction motor drives, parameter off-line identification, parameter on-line estimation, vector control. Preprint Order Number: PE-029EC (04-2002) Discussion Deadline: September 2002
Cho, H.S.; Jung, H.S. Author Affiliation: Seoul National University, Seoul, Korea Abstract: The force equation of a synchronous permanent magnet planar motor (SPMPM) is investigated. The flux density distribution of a two-dimensional magnet array for a SPMPM was obtained by solving the equations of the scalar magnetic potential. The expressions of the force and hack-EMF constant were derived and examined. Using these expressions, the conditions for normal operation of the SPMPM were found and the optimal design was determined in order to maximize the force of the SPMPM. Keyword: Terms-back-EMF, force constant, permanent magnet, planar motor. Preprint Order Number: PE-489EC (04-2002) Discussion Deadline: September 2002
Online Identification of the Mutual Inductance for Vector-Controlled Induction Motor Drives
Energv Develonment and Power Generti-nn
Levi, E.; Wang, M. Author Affiliaiton: Liverpool John Moores University, Liverpool, U.K.; Chongqing University, Chongqing, China Abstract: Mutual inductance of an induction machine may vary considerably when the flux reference varies. An important and frequent application of a variable flux reference is the operation in the field-weakening region. Standard assumption of constant mutual inductance is no longer valid and it becomes necessary to compensate for the mutual inductance variation. This paper proposes a novel method for on-line mutual inductance identification in vector-controlled induction machines. The method is characterized with a very simple structure, ease of implementation, very low parameter sensitivity, and the capability to provide an accurate estimate under both transient and steady-state operating conditions. Full experimental verification of the proposed scheme is provided and a number of potential applications in a vector-controlled induction motor drive are discussed. Keywords: Induction motor drives, main flux saturation, mutual inductance identification, vector control. Preprint Order Number: PE-439EC (04-2002) Discussion Deadline: September 2002
High-Speed Performance Improvements of
a Two-Phase Switched Reluctance Machine Utilizing Rotor Conducting Screens Hamdy, R.; Fletcher, J.E.; Williams, B.W; Finney, Sj. Author Affiliation: Heriot-Watt University, Edinburgh, Scotland, U.K. Abstract: The two-phase 4/2 switched reluctance machine is suitable for high-speed operation. It has a simple and robust construction and can be operated from power converters that have no shoot-through 52
Variable-Speed Wind Power Generation Using a Doubly Fed Wound Rotor Induction Machine: A Comparison with Alternative Schemes Datta, R.; Ranganathan, VT.
Author Affiliation: ABB Corporate Research Center, Ladenburg, Germany; Indian Institute of Science, Bangalore, India Abstract: In this paper, a wind energy conversion system (VVECS) using a grid-connected wound rotor induction machine controlled from the rotor side is compared with both fixed-speed and variable-speed systems using a cage rotor induction machine. The comparison is done on the basis of major hardware components required, operating region, and energy output due to a defined wind function using the characteristics of a practical wind turbine. Although a fixed-speed system is more simple and reliable, it severely limits the energy output of a wind turbine. In the case of variable-speed systems, comparison shows that using a wound rotor induction machine of similar rating can significantly enhance energy capture. This comes about due to the ability to operate with rated torque even at supersynchronous speeds; power is then generated out of the rotor as well as the stator. Moreover, with rotor side control, the voltage rating of the power devices and dc bus capacitor bank is reduced. The size of the line side inductor is also decreased. Results are presented to show the substantial advantages of the doubly fed system. Keywords: Rotor side control, subsynchronous and supersynchronous generation, variable speed constant frequency operation, wind energy conversion system, wind turbine, wound rotor induction machine. Preprint Order Number: PE-558EC (04-2002) Discussion Deadline: September 2002 IEEE Power Engineering Review, July 2002
