This paper proposes a simple procedure for accurate identification of the magnetic model of permanent-magnet synchronous machines through inverter supply. The proposed method accounts for the magnetic saturation and the cross-saturation effects. The identification methods reported in the literature may require a servomotor to drive the motor under test at controlled constant speed or the motor itself must accelerate and decelerate. The technique proposed here can be applied at standstill with or without rotor locking and uses a dc+ac injection strategy to identify the machine inductances to construct its magnetic model. The direct current sets the operating point, whereas the superimposed ac component estimates the inductance at that particular point. Small ac signal is injected to ensure local linearity of the magnetic characteristic. Saturation effects are automatically accounted for by the dc bias level, and cross-saturation effects are quantified through maintaining a constant current along the cross-axis. The magnetic model thus obtained can be used for optimal control of the machine and for accurate torque estimation in vectorcontrolled drives.
A Z-source converter is an unique x-shaped impedance network called Z-source impedance network that couples the converter main circuit to the power source. The converter may be of all conversion types -if it is of ac-to-dc type, the z-source converter is called z-source inverter. Since 2003 when this recently conversion concept appeared [1], it proved able to solve many conversion problems. In this paper it's superiority compared to traditional solutions are shown. There are also small disadvantages and limitations revealed.
The present paper proposes the use of the opposition method to evaluate the performance of a wireless power transfer system. The work is focused on the effect related to the insertion of conductive or ferromagnetic components that are materials typically adopted in the realization of this kind of systems. Index Terms-Inductive power transmission -Loss measurement -Mutual coupling -Resonant inverters -Wireless power transmission
In this paper, a loss-minimizing strategy is proposed for induction motor drives to ensure maximum efficiency operation for a given torque demand. The proposed strategy directly regulates the machine stator flux according to the desired torque, using an optimal stator flux reference. Therefore, the proposed strategy is suitable for motor control schemes that are based on direct flux regulation, such as direct torque control or direct flux vector control. The maximum efficiency per torque (MEPT) stator flux map is computed offline using the traditional no-load and short-circuit tests' data.
An iron loss model based on the stator flux and frequency is also proposed for the calibration of the machine loss model and also for on-line monitoring of the iron losses during motor operation. The proposed MEPT strategy has been validated on a 2.2 kW induction machine and the motor efficiency has been measured for different speed values and variable load conditions. The experimental results confirm the effectiveness of the proposed solution. specific resistivity of core material [Ω·m] I.
0093-9994 (c)
APPENDIXThe IM rated data and parameters are: rated power 2.2 kW, rated voltage 400V, rated current 5.08A, rated frequency 50Hz, rated speed 1400 rpm, rated torque 15 Nm, R s = 3.37 (25C), R r = 2.2 (25C), L ls = L lr = 16 mH.
The paper presents a novel technique for an accurate identification of the inverter nonlinear effects, such as the dead-time and on-state voltage drops. The proposed technique is very simple and it is based only on a current control scheme. If the inverter load is an AC motor, the inverter effects can be identified at drive startup using as measured quantities the motor currents and the inverter DC link voltage. The identified inverter error is stored in a Look-Up Table (LUT) that can be subsequently used by the vector control algorithm. The proposed method has been tested on a 1 kVA inverter prototype and the obtained results demonstrate the feasibility of the proposed solution.
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