Recently the energy electronics comes to attention that energy saving effects to meet global environment problems. The evolution of home appliances and mobile devices have been realized by efficient frequency converter which are low cost and small size. This paper presents recent trend of energy electronics applied to home appliances and mobile devices.
First of all, this paper proposes a new dynamic mathematical model of surface-mounted permanent magnet synchronous motors (SPMSMs) with flux saturation phenomena, in stationary reference frame. Secondly, based on the dynamic model, this paper establishes new dynamic simulators taking flux saturation phenomena into account, which act as very powerful tools for developing initial-rotor-position estimation methods for SPMSMs. Thirdly, this paper proposes a new initial-rotor-position estimation method for SPMSMs. The proposed method is so simple that it inputs a spatially rotating high-frequency voltage to SPMSMs, measures current output and can estimate directly rotor position of N-pole through norm evaluation of the current. The method exploits flux saturation phenomena inherent to SPMSMs and is insensitive to all motor parameters. According to experiments, the maximum estimation error is about ±0.035(rad) (±2(degree)) in mechanical sense, which is comparable to sensor mounting error and is sufficient small for initial drive of SPMSMs.
A matrix converter (MC) is a three-phase AC-to-AC direct converter without any energy storage requirement. It is expected to be a next generation converter by reason of possibilities of small size and high efficiency. At present, there are some problems to prevent it from being used practically. One of the problems is the distortion in the input current. The control methods proposed so far have not realized the enough reduction of the input current harmonics compared with conventional PWM rectifiers. As a solution to these problems, many approaches have been proposed. In the present paper, an improved PWM method that can achieve both sinusoidal input and output currents simultaneously is considered. In this method, the MC is treated as a controlled voltage source viewed from the load side. On the other hand, it is treated as a controlled current source viewed from the line side. The proposed control method is based on the mathematical expression of the function of the PWM operation of MC. To improve the input current waveform, two line-to-line voltages of the three-phase line are used to control the output current. The output duty ratio of the two line-to-line voltages is utilized to improve the input current waveform without affecting the controllability of the output current. In addition, the compensation of the variations in the line voltage and the output current are introduced. In this way, the proposed method can realize the sinusoidal input and output currents. The effectiveness of the proposed control method is confirmed by some experimental results employing a laboratory prototype.
This paper describes a method to analyze harmonic components of the air-gap flux density distribution on 3-phase cage induction motors, considering the influence of circumferential slot arrangement, stator winding pattern and distribution of air-gap permeance by leakage flux. The applied method is based on an analytical model of the permeance and the magneto-motive force distributions with non-linear model considering main and leakage flux saturation. The proposed method is applied to the analysis of a cage induction motor at load and locked rotor conditions. As a result, the harmonic components of the air-gap flux density distributions at different driving conditions are shown quantitatively. The accuracy of the proposed method is confirmed by comparison with the finite element magnetic field analysis. From the comparison of these calculated results, the proposed method is shown to be appropriate and useful for quantitative estimation of harmonic flux for cage induction motors.
These days, a quiet induction motor is in great demands. In low speed motor with 4 poles and 6 poles, electromagnetic noise is predominant in acoustic noise. Most electromagnetic vibration and noise is originated from combination of harmonic fluxes in the air gap. Space distribution of fundamental and harmonic fluxes was studied using search coil, FEM analysis and equations. Harmonic fluxes including fundamental one were measured with 36 search coils on inner surface of the stator teeth. From this experiment, flux space distribution in each flux frequencies was obtained. Flux space distribution was also analyzed by FEM. These results were analytically checked by mathematical equation. From these stuff, space flux distribution mode, for various harmonics was confirmed. This result will be useful for quiet motor design.
This paper proposes a small-sized passive EMI filter for the purpose of eliminating high-frequency shaft voltage and ground leakage current from an ac motor. The motor is driven by a general-purpose PWM inverter connected to a three-phase grounded voltage source. The passive EMI filter requires access to the ungrounded neutral point of the motor. This unique circuit configuration makes the common-mode inductor effective in reducing the high-frequency common-mode voltage generated by the PWM inverter with a carrier frequency of 15kHz. As a result, both high-frequency shaft voltage and ground leakage current can be eliminated very efficiently. However, the common-mode inductor may not play any role in reducing the low-frequency common-mode voltage generated by the diode rectifier, so that a low-frequency component still remains in the shaft voltage. Such a low-frequency shaft voltage may not produce any bad effect on motor bearings. The validity and effectiveness of the EMI filter is verified by experimental results obtained from a 200-V 5-kVA laboratory system.
A simplified vector control is proposed as a driving method of permanent magnet synchronous motor (PMSM) for electrical household appliances. Control structure is simplified by eliminating the speed regulator and the current regulator from the conventional vector controller. Output voltage references are determined by feedforward-like calculation using motor parameters, rotation speed command, and current references. In the static characteristic, the proposed vector control method is almost equal to the conventional one, because the voltage references are calculated in the vector space. A practical estimate equation of rotor position is proposed, and the phase locked loop control approach is employed to drive PMSM without position and speed sensors. Design method of two control gains is given. Finally, the effectiveness of the proposed control is verified by simulation and experiments.
This paper deals with a leakage current flowing out of the heat sink of a voltage-source PWM inverter. The heat-sink leakage current is caused by a steep change in the common-mode voltage produced by the inverter. It flows through parasitic capacitors between the heat sink and power semiconductor devices when no EMI filter is connected. Experimental results reveal that the heat-sink leakage current flows not into the supply side, but into the motor side. These understandings succeed in describing an equivalent common-mode circuit taking the parasitic capacitors into account. The authors have proposed a passive EMI filter that is unique in access to the ungrounded motor neutral line. It is discussed from this equivalent circuit that the passive EMI filter is effective in preventing the leakage current from flowing. Moreover, installation of another small-sized common-mode inductor at the ac side of the diode rectifier prevents the leakage current from flowing into the supply side. Experimental results obtained from a 200-V, 3.7-kW laboratory system confirm the effectiveness and viability of the EMI filter.
This paper presents a new characteristics analysis of dynamic mathematical model for synchronous reluctance motor, which is recently attracting attentions in conjunction with the problem of rotor phase selection and estimation based on the extended BEMF (back electromotive force) for sensorless drive. This paper gives the following new characteristic results in a simple unified analytical manner. 1) Change between positive and negative salient pole phases requires basically no modification to the dynamic mathematical model in the general reference frame. 2) Selection of positive or negative salient pole phase as rotor phase is no more than a preference of designers. 3) There exists a very simple deriving method of two stator flux models for explicit expression of the extended BEMF. 4) At least, four circuit equations with the extended BEMF exist, which are equivalent to each other on the same reference frame. 5) There exists duality among the four circuit equations from viewpoints of rotor phase selection. 6) The duality reinforces the above-mentioned results 1) to 5). Main results of this paper correct or reinforce the results recently reported by others.
In this paper, we investigate effects of harmonic electromagnetic field to torque characteristics of induction motors from both side of experiment and electromagnetic field analysis. The characteristics of two kinds of the aluminum cage three-phase induction motors are measured and calculated. One is with the closed rotor slots. The other is semi-closed. In the experiment, the negative torque at synchronous speed is measured by driving the induction motor by the synchronous permanent magnet motor. The total torque at load condition is also measured by the torque detector. In the analysis, the harmonic magnetic fields, the harmonic losses and the harmonic torques at each time and space harmonic order are calculated using the nonlinear time-stepping finite element method to clarify the mechanism of the harmonic torque generation. The measured and the calculated results agree well. It is clarified that the negative torque caused by the slot harmonics at the rated load condition is not negligible and that the negative torque is mainly generated by the harmonic core losses.
This paper newly shows applicability of the generalized integral type PLL method to sensorless vector controls of permanent magnet synchronous motors using full-order state observer, which have identified rotor speed as a system parameter separately from rotor phase treated as a system state by adaptive identification algorithm so far. The PLL method can exploit the integral-derivative relation between phase and speed, consequently can allow simpler realization of the sensorless vector controls.
In this paper, the authors propose a method for detecting human region from the image by using the local binary pattern. This method is not influenced against the image obtainment environment. The local binary pattern expresses the adaptive change of the pixel value distribution. The difference of the pixel value of the neighbour in the object pixel is encoded. It is possible to carry out the region segmentation accuracy, because the code pattern depends on the texture in the image. The result of the experiment is shown in this paper in order to verify the effectiveness of this method.
In a conventional positioning system, when the position error becomes small, the motor cannot obtain enough deceleration torque. Hence, the position response becomes slow. In order to overcome this problem, this paper proposed a new high speed positioning system of an AC servo-motor considering unknown coulomb friction, inertia variation and windup phenomenon. In this paper, the sum of coulomb friction load and inertia variation are estimated by disturbance observer. The proposed method always uses the maximum acceleration torque, the deceleration torque and maximum speed.
This paper presents a DD ASEM (Direct Drive Applications-Specific Electric Motors) for electric injection molding machine. A new driving system is presented,which realizes both high injection speed and quick response. In the new driving system, a ball screw is driven by ASEM directly without pulleys and belts. The basic design for the ASEM is presented with an emphasis on the selection of pole number and slot number.