Simulation research on high-speed motor current harmonic elimination methods

A large number of harmonics will be generated in the process of transforming high frequency and high voltage alternating current (AC) into a constant frequency and constant voltage through a power conversion system when the high-speed motor is used as a generator. The phase-shifting reactor is used to eliminate harmonics for high-speed generator power conversion systems, and LCL filter and adjustable inductance filter are used to eliminate harmonics for high-speed motor power supply system in this paper. The adjustable inductance filter can adjust the inductance value in time according to the change of the output frequency of the inverter. The results verify the effectiveness of the methods used, and provide a theoretical basis for the wide application of high-speed motor by simulation.

Development of the dual-channel frequency meter for measurements with hydrostatic pressure sensor

The paper describes the process and the results of development of the dual-channel frequency meter, which function is to measure the output frequency generated by bottom-mounted pressure sensors. The sensors are actively used to monitor the marine environment. AVR family microcontrollers were used as the computing core of the presented device. This solution allows to obtain far lower power consumption, which is especially important when operating with no industrial power supply system in the coastal zone. As a result, we can deploy a reliable monitoring equipment capable of long-term saving data and if necessary transmit it for further processing. The developed frequency-meter is able to continually record the ambient temperature, atmospheric pressure and dynamically varying output frequency, which depends on hydrostatic pressure (sea level). To obtain more accurate data, we implemented a frequency measure method called reciprocal counter with lower relative error not affected by value of the output frequency. A laboratory experiment has been conducted, which confirms the suitability of the developed frequency meter for field-oriented conditions.

A 0.8 V, 5.3–5.9 GHz Sub-Sampling PLL with 196.5 fsrms Integrated Jitter and −251.6 dB FoM

This paper proposes a hybrid dual path sub-sampling phase-locked loop (SSPLL), including a proportional path (P-path) and an integral path (I-path), with 0.8 V supply voltage. A differential master–slave sampling filter (MSSF), replacing the sub-sampling charge pump (SSCP), composed the P-path to avoid the degraded feature caused by the decreasing of the supply voltage. The I-path is built by a rail-to-rail SSCP to suppress the phase noise of the voltage-controlled oscillator (VCO) and avoid the trouble of locking at the non-zero phase offset (as in type-I PLL). The proposed design is implemented in a 40-nm CMOS process. The measured output frequency range is from 5.3 to 5.9 GHz with 196.5 fs root mean square (RMS) integrated jitter and −251.6 dB FoM.

Controlled Energy Flow in Z-Source Inverters

This paper proposes a method to reduce the output voltage distortions in voltage source inverters (VSI) working with impedance networks. The three main reasons for the voltage distortions include a discontinuous current in the coils of the impedance network, the double output frequency harmonics in the VSI’s voltage output caused by insufficient capacitance in the impedance network, and voltage drops on the bridge switches during the shoot-through time. The first of these distortions can be reduced by increasing the current of the impedance network when the output VSI current is low. This method requires storing energy in the battery connected to the DC link of the VSI during the “non-shoot through” time. Furthermore, this solution can also be used when the Z-source inverter works with a photovoltaic cell to help it attain a maximum power point. The Z-source inverter is essentially a voltage source inverter with the Z-source in the input. In this paper, the theory behind basic impedance networks of Z-source and quasi-Z-source (qZ-source) is investigated where simulations of the presented solutions and experimental verification of the results are also presented.

On dissection of the uterine wall during laparoscopic myomectomy

BACKGROUND: Laparoscopic myomectomy is becoming the leading method of surgical treatment of uterine fibroids while preserving reproductive and menstrual functions. Increasingly, ultrasound energy is used to dissect the myometrium. Meanwhile, the mode and direction of the ultrasound energy supply to minimize damage to the underlying tissues have not been specified. AIM: The aim of this study was to perform a comparative analysis of the myometrium and the fibroid pseudocapsule in the projection of the myoma nodule after dissection using ultrasound energy with different initial characteristics of the surgical instrument. MATERIALS AND METHODS: For comparison, we selected two instruments with a longitudinal ultrasound energy supply with an output frequency of 80 MHz ... 2.5 GHz and 47 kHz at intermittent operating mode of 5/10 sec and one torsion instrument with a transverse ultrasound energy supply with an output frequency of 36 kHz at intermittent operating mode of 3/30 sec. RESULTS: Our study has shown that the smallest zone of irreversible changes is formed when using ultrasound energy with an output frequency of 36 kHz at intermittent operating mode of 3/30 sec with its transverse feed at 90 degrees to the blade, and the largest zone of irreversible changes is formed when using ultrasound energy with an output frequency of 47 kHz at intermittent operating mode of 5/10 sec with its longitudinal feed. CONCLUSIONS: Morphometric studies with an analysis of the depth of necrotic and necrobiotic changes in the myometrial tissue showed that from the standpoint of reproductive surgery, it is preferable to use USE with an output frequency of 36 kHz at intermittent operating mode of 3/30 sec with its transverse feed.

Microwave cyclotron protective devices for radar receivers

Brief overview of the latest developments of microwave cyclotron protective devices, their functioning and parameters is given. It is noted that these devices have a number of important advantages over other types of protective devices: they are autonomous, provide no peak of microwave power leaking to the output, frequency filtering and low noise figure (0.7-1.2 dB). The upper limit of the linearity of cyclotron protective devices in the signal transmission mode when the transmission coefficient is compressed by 1 dB is ~ 1 mW. The devices can operate with an input pulse power of up to 10 kW or more, while the attenuation of the input power in the protection mode is more than 60-80 dB. The recovery time of parameters after the end of a powerful input pulse is 10-20 ns. For devices of the 3-cm wavelength range, experimental data are given on the recovery time, the upper limit of linearity, attenuation of the input power in the protection mode, and filtration characteristics.

A Simple Two-Stage AC-AC Circuit Topology Employed as High-Frequency Controller for Domestic Induction Heating System

The induction heating process at a domestic level is getting attention nowadays as this power converting topology ensures clean, reliable, flexible, and fast operation. The low input frequency is converted to required regulated high output frequency with indirect and direct power converting approaches. The circuit and control complexity and high conversion losses associated with indirect power converting approaches lower their uses for domestic induction systems. The direct ac-ac power conversion approach is one of the viable solutions for low and medium power level loads, especially for domestic induction heating loads. The circuit complexity, cost, and conversion losses of the direct power converting systems depend on the number of the controlled switching devices as each controlled switch requires one gate driving circuit and one isolated dc supply. Simplified pulse width modulation (PWM) switching control also lower their control effort. Therefore, in this article, a simplified direct ac-ac power converting approach is introduced for a high-frequency domestic induction heating system. Here, the regulation of the high output frequency is achieved by simply cascading the single-phase full-bridge rectifier with a full-bridge inverter with a simple control strategy. The characteristics of the developed topology are validated through simulation results of the Simulink-based platform and practical results of the developed practical setup.