Q-axis Inductance Research Articles

Determination of direct and quadrature axis inductances of synchronous reluctance motors with allowance for cross saturation

AbstractThe d‐axis inductance of reluctance motor is affected by not only the d‐axis current but also the q‐axis current, because of cross magnetic saturation between the direct and quadrature axes. This situation is similar for the q‐axis inductance. The authors propose a method to determine the d‐axis inductance related to the d‐ and q‐axis currents and the q‐axis inductance related to the d‐ and q‐axis currents from a standstill test. This method involves the following four steps. First a rectangular‐wave voltage, alternated between plus and minus, is applied to the two armature winding terminals after breaking the rotor in the d‐axis position. Secondly, the voltage and current between the terminals are measured. Thirdly, the d‐axis inductance related with d‐axis current is calculated from the voltage and current. Finally, the process above is repeated when a DC current flows from the remaining armature terminal to neutral point terminal and the d‐inductance related to the d‐ and q‐axis currents is derived. A similar treatment applies when determining the q‐axis inductance related to the d‐ and q‐axis currents in the q‐axis rotor position. The method is implemented on a 1.1 kW–178 V–6.3 A‐4P–2200 min−1 flux barrier type reluctance motor. Results of load performance on a vector controlled reluctance motor measured by on‐load tests and calculated from the d‐ and q‐axis inductances obtained by the proposed method clearly demonstrate the validity of the proposed method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 52–59, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10377

Parameter Identification of PM Motor System at Standstill

This paper proposes the on-line parameter identification method of PM motor system including inverter. The d and q-axis inductances, phase resistance and voltage drop of inverter can be identified from the detected currents and voltage references at standstill. The validity of the proposed method is confirmed by experimental results.

A saturating lumped-parameter model for an interior PM synchronous machine

This paper presents a lumped-parameter magnetic model for an interior permanent-magnet synchronous machine. The model accounts for the effects of saturation through a nonlinear reluctance-element network used to estimate the q-axis inductance. The magnetic model is used to calculate inductance and torque in the presence of saturation. Furthermore, these calculations are compared to those from finite-element analysis with good agreement.

Improvement of control characteristics of interior permanent-magnet synchronous motor for electric vehicle

This paper describes a method to improve the control characteristics of an interior permanent-magnet synchronous motor for an electric vehicle (EV). At the motor for an electric vehicle, d- and q-axes inductances are varied to a great extent. Therefore, variation characteristics for d- and q-axes inductances are analyzed as a function of both current magnitude and current phase angle. A new vector control algorithm is proposed that makes use of the learning capability of a neural network to implement d- and q-axes inductances to be varied according to current magnitude and also current phase angle. Also, a distribution law of torque reference to improve the driving characteristics of the two motor-driven EV is proposed. Advanced performance is verified through numerical methods and experiments.

Mechanical-sensorless robust control of permanent-magnet synchronous motor using phase information of harmonic reactive power

This paper proposes a novel control strategy of a permanent-magnet synchronous motor without mechanical sensors. The strategy is based on use of harmonic reactive power and utilizes its relative phase information to estimate the rotor position, i.e., d-axis direction that corresponds to the magnetic poles on the rotor. The harmonic reactive power can be calculated by filtering a specific harmonic voltage vector and a harmonic current vector and is never affected by variation of the winding resistance that may be caused by temperature fluctuation or a skin effect due to the harmonics. Since the harmonic reactive power has a relative phase with respect to a phase reference signal, which is proportional to the estimation error of the rotor position, the estimated position converges to the true value by zeroing the phase shift. To achieve this estimation algorithm, a phase-locked-loop (PLL) technique is employed in the rotor position estimator. In the PLL, the harmonic reactive power is converted to a digital pulse to extract only the relative phase information and to eliminate amplitude information that is relevant to d-axis and q-axis inductance and the rotor speed. Therefore, the proposed estimation technique is almost perfectly robust against every motor parameter and any operating conditions. The paper describes a theoretical aspect of the method and presents several computer simulation and experimental results to show the feasibility of the proposed strategy.

Optimum design of a multilayer interior permanent magnet synchronous motor using reluctance torque

The report analyzes the results of experiments done with an inverter drive interior permanent-magnet (IPM) motor. We examine results of both FEM (finite element method) simulation and experiments using a prototype motor with identical conditions set for stator and magnet volume. The results indicated that with magnets implanted inside the rotor, the values for the d-axis inductance of the motor remained roughly the same, unaffected by the shape or number of layers. However, the q-axis inductance exhibited significant change. This research report compares an IPM motor having two layers of permanent magnets with a motor having a single layer. The dual layer shows a 30% or greater increase in torque using the same current. These results indicate that this motor is especially effective for such applications as robots, plant machinery, compressor motors, and electric vehicles. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 64–72, 1999

Design considerations for permanent magnet synchronous motors for flux weakening applications

The required parameter values of a permanent magnet synchronous motor designed for very large power-speed range are determined based on a linear dq model. It is shown that unconventional motor constructions with the d-axis inductance equal to, or bigger than, the q-axis inductance can provide superior torque, power factor and control characteristics. The initial sizing state of a design procedure is described. Analytical equations are developed and used to illustrate the influence of the rotor configuration, electromagnetic loading and air-gap length on the performance of a relatively large range of medium-sized motors. Suggestions regarding the improvement of efficiency, power factor, overload performance and PM protection against permanent demagnetisation are also given. The results of the analytical design procedure have been checked against finite element computations and experimental data.

Parameters and volt-ampere ratings of a synchronous motor drive for flux-weakening applications

This paper deals with the selection of the motor parameters and the inverter power ratings for a permanent magnet (PM) synchronous motor drive in order to meet a given flux-weakening torque versus speed characteristic. Appropriate combinations of stator PM flux linkage, d- and q-axis inductances, and inverter current rating at a given voltage are derived, in normalized values, as functions of the specified flux-weakening speed range and torque limits. By means of these sets of data, the drive designer can easily individuate and compare all the suitable synchronous motors (defined by the d- and q-axis inductances and flux linkage) and the related inverter volt-ampere ratings, for the desired flux-weakening performance. Therefore, this paper can be considered a synthesis work rather than an analysis one and can profitably be used for an optimal design of a synchronous motor drive.

Optimum design of a multi layer interior permanent magnet synchronous motor using reluctance torque

This report analyzes the results of experiments done with an inverter drive interior permanent magnet (IPM) motor. We examine results of both FEM (Finite Element Method) simulation and experiments using a prototype motor with identical conditions set for stator and for magnet volume. The results indicated that with magnets implanted inside the rotor, the values for the d-axis inductance of the motor remained roughly the same, unaffected by shape or number of layers. However, the q-axis inductance exhibited significant change. This research report compares an IPM motor having two layers of permanent magnets with a motor having a single layer. The dual layer shows a 30 percent or greater increase in torque using the same current. These results indicate that this motor is especially effective for such applications as robots, plant machinery, compressor motor, and electric vehicles.

CAPACITOR BRAKING OF SYNCHRONOUS RELUCTANCE MOTORS

ABSTRACT Capacitor braking, a well-known low-loss braking method of Induction ma-chines, Is described in connection with reluctance machines. To represent the main features of capacitor braking of synchronous reluc-tance motors, three dimenslonless quantities are introduced: a frequency parameter, a reactance parameter and a resistance parameter. With the load angle of the synchronous machine added, the result is a four-parameter description of the braking process. The theoretical values for speed range and braking torque are compared with the experimental results of a 22 kW 4-pole test machine. Thanks to the large difference between the d-axis and q-axis inductances of the spe-cial barrier rotor in the test machine, a sufficiently broad braking speed range can be obtained.

Servo drive system and control characteristics of salient pole permanent magnet synchronous motor

Permanent magnet (PM) synchronous motors fed by PWM inverters are considered. PM motors sometimes have a saliency, in which the q-axis inductance is larger than the d-axis inductance. A high-performance servomotor drive system for a salient-pole PM motor is described. An armature current vector is actively controlled according to load conditions in order to use a reluctance torque effectively, and, as a result, a large torque can be produced. The control algorithm for the armature current vector is described, taking the demagnetization of the PM and the magnetic saturation into account. Characteristics such as torque, power factor, efficiency, power capability, transient responses, etc. are examined in detail by computer simulations and experimentally.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>