Commutation Circuit Research Articles

Blowers of Vacuum Cleaners Utilizing Coreless and Sensorless Axial-Flux Motors with Edge-Wire Coils

Axial-flux motors (AFM) generally have higher torque and power densities, smaller volume and weight, larger diameter to length ratio, and compact construction for the same power level than radial-flux motors (RFM). Hence, AFM are attractive alternative to conventional RFM for applying in low torque and speed servo control systems. Additionally, magnetic Hall-effect sensors and commutation circuits are unsuitable for environment with high temperature and restricted space, so sensorless driving control method of AFM by detecting zero-crossing of back-EMF signals has been achieved. Furthermore, coreless design can reduce motor total weight, normal attractive force and torque pulsation and can increase efficiency of machines as compared with conventional design with cores. Thus, this study focuses on sensorless AFM design applying for blowers in vacuum cleaners to follow the concepts of axial-flux, edge-wire with high space-utilization factors, and stators without ferromagnetic cores. The closed-loop velocity controller designs by adopting proportional-integral-derivative (PID) and fuzzy logic control (FLC) algorithms have been demonstrated effectively for the design sensorless AFM of blowers in vacuum cleaners. As a result, the settling time of velocity closed-loop control methods can be converged within 1.0 second; i.e. the vacuum cleaners can switch and operate in various speeds with different operational environment rapidly. Therefore, the system characteristics and lifetime of the designed sensorless AFM have been enhanced and satisfied the demands of blowers to employ in vacuum cleaners.

Improvement of solid-state circuit breaker operation in commutation circuit

In solid-state circuit breakers (SCBs), the discharging time of the commutation capacitor is high; hence, the performance of the SCB is affected. In the paper, the performance of SCB is improved by addition of a digital switch, and current comparator is added in the place of commutation capacitor. The fault current is calculated by the current comparator. At fault condition, the fault current is reduced by opening the digital switch. If the digital switch is opened, an open circuit is formed quickly and is compared to commutation capacitor discharging time. This leads to improved performance of SCB in handling short circuit failure. The performance of the proposed commutation circuit is evaluated.

Improvement of Solid-State Circuit Breaker Operation in Commutation Circuit

In solid-state circuit breakers (SCBs), the discharging time of the commutation capacitor is high; hence, the performance of the SCB is affected. In the paper, the performance of SCB is improved by addition of a digital switch, and current comparator is added in the place of commutation capacitor. The fault current is calculated by the current comparator. At fault condition, the fault current is reduced by opening the digital switch. If the digital switch is opened, an open circuit is formed quickly and is compared to commutation capacitor discharging time. This leads to improved performance of SCB in handling short circuit failure. The performance of the proposed commutation circuit is evaluated.

Modelling and Simulation of Cost Effective Sensorless Drive for Brushless DC Motor

This paper deals with a new commutation approach to achieve the sensorless drive of permanent magnet BLDC motor over the conventional six switch commutation circuitry. In the simulation model, we have introduced four switch three phase Brushless DC (BLDC) motor drive in which the rotor position is estimated using back EMF detection technique. In sensorless concept, the electronic commutation circuit plays an important role to drive motors because of their non-self commutating nature. In this work, power electronics based inverter along with logical circuitry has been employed in order to perk up the sensorless technique of BLDC motor. This driving procedure is always advantageous over sensored drives of BLDC motors, which come with bulky module using Hall-effect position sensors to detect the rotor position. Thus, this sensorless performance not only reducing the hardware complexity but also minimizes the consumption of power by associated circuitry. The effectiveness of the design is demonstrated through simulation results. The performance of this design is first evaluated by MATLAB based SIMULINK platform which gives a satisfactory result. Finally, this study helps us to develop a real time implementation of cost effective drive without hall sensors for BLDC motor.

Accelerating commutation circuits in quantum computer networks

In a high speed and packet-switched quantum computer network, a packet routing delay often leads to traffic jams, becoming a severe bottleneck for speeding up the transmission rate. Based on the delayed commutation circuit proposed in Phys. Rev. Lett. 97, 110502 (2006), we present an improved scheme for accelerating network transmission. For two more realistic scenarios, we utilize the characteristic of a quantum state to simultaneously implement a data switch and transmission that makes it possible to reduce the packet delay and route a qubit packet even before its address is determined. This circuit is further extended to the quantum network for the transmission of the unknown quantum information. The analysis demonstrates that quantum communication technology can considerably reduce the processing delay time and build faster and more efficient packet-switched networks.

Facilities for ice melting on electric transmission lines

Methods of ice melting on electric transmission lines using diode and thyristor rectifiers are considered. To shorten the melting time of ice and to simplify the commutation circuit at substations, it is suggested to use multipole converters based on thyristor frequency converters with a direct connection.

A Novel VSI- and CSI-Fed Active–Reactive Induction Motor Drive with Sinusoidal Voltages and Currents

Till date load-commutated inverter (LCI)-fed synchronous motor drive configuration is popular in high power applications (>;10 MW). The leading power factor operation of synchronous motor by excitation control offers this simple and rugged drive structure. On the contrary, LCI-fed induction motor drive is absent as it always draws lagging power factor current. Therefore, complicated commutation circuit is required to switch off thyristors for a current source inverter (CSI)-driven induction motor. It poses the major hindrance to scale up the power rating of CSI-fed induction motor drive. A new power topology for LCI-fed induction motor drive for medium-voltage drive application is proposed. A new induction machine (active-reactive induction machine) with two sets of three-phase winding is introduced as a drive motor. The proposed power configuration ensures sinusoidal voltage and current at the motor terminals. The total drive power is shared among a thyristor-based LCI, an insulated gate bipolar transistor (IGBT)-based two-level voltage source inverter (VSI), and a three-level VSI. The benefits of SCRs and IGBTs are explored in the proposed drive. Experimental results from a prototype drive verify the basic concepts of the drive.

Sensitive load voltage compensation against voltage sags/swells and harmonics in the grid voltage and limit downstream fault currents using DVR

In the past decades, the power quality (PQ) has become a critical issue in highly automated industries and sensitive load centers. The voltage quality is the most important part of the PQ for customers. The voltage disturbances in the form of voltage sags, swells and harmonics can cause huge financial losses. In the past few years, the power electronic solutions have been proposed to avoid these problems. The dynamic voltage restorer (DVR) is one of the solutions. This paper proposes a new topology for single-phase DVR which is able to compensate multiple voltage disturbances and limit the downstream fault currents with a simple topology. The proposed DVR is based on the single-phase direct ac/ac converter which is energized from the main grid. As a result, there is no need for energy storage elements and dc link capacitors. The proposed topology can deal with high voltage with low voltage rating switches. Therefore, the switches can be IGBTs without needing an auxiliary forced commutation circuit as in thyristors which are high voltage switches. The performance of the proposed topology is validated by digital simulations and a laboratory scale prototype implementation.

A new family of marx generators based on commutation circuits

This paper presents a novel topology for the generation of high voltage pulses that uses both slow and fast solid-state power switches. This topology includes diode-capacitor units in parallel with commutation circuits connected to a positive buck-boost converter. This enables the generation of a range of high output voltages with a given number of capacitors. The advantages of this topology are the use of slow switches and a reduced number of diodes in comparison with conventional Marx generator. Simulations performed for single and repetitive pulse generation and experimental tests of a prototype hardware verify the proposed topology.

Simulation and Analysis of a Multilevel Converter Topology for Solar PV Based Grid Connected Inverter

There has been a noticeable increase in use of Solar PV based systems for power generation, given its renewable nature. A solar PV based grid tie inverters are used for dc-ac conversion. The conventional line commutated ac-to-dc inverters have square-shaped line current which contains higher-order harmonics. The line current with the high harmonic contents generates EMI and moreover it causes more heating of the core of distribution/power transformers. Alternatively, PWM based inverters using MOSFET/IGBT switches are also used for the same purpose. However, apart from higher switching losses, the power handling capability and reliability of these devices are quite low in comparison to thyristors/SCR. Nevertheless, the conventional thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal line current or waveform with low har- monic contents is the most desirable. In the present work, a multilevel line commutated inverter topology has been proposed and analyzed which improves the wave shape and hence reduces the total harmonic distortion (THD) of the line current in a grid tie line commutated inverter. The scheme has successfully been implemented and tested. Moreover, the performance of the proposed topology is far better than the conventional line-commutated inverter. It reduces THD, losses, switching stress and EMI.

Experimental Verification of Current-Source Inverter With ZVS Commutation Circuit

This paper presents a current-source inverter suitable for high-voltage/high-power motor drives. This inverter uses thyristors as main switching devices and utilizes a zero-voltage-switching (ZVS) commutation circuit. It has the advantages of good motor power factor and self-startability. We have evaluated a test model of the proposed inverter and a motor and verified that the inverter operates at a motor power factor of one and that it can be started even when the motor speed is zero. Moreover, a six-phase synchronous motor was driven by two of these inverters; it was confirmed that they decreased the motor torque ripple and the harmonic component of the voltage source. In addition, we evaluated the operation of the ZVS commutation circuit by simulation and experiment and thus verified that turnoff loss depends mainly on the inductance of the ZVS commutation circuit and not on gate resistance. Moreover, when the switching device turns off the current, its voltage is almost zero. That is, even if the inductance is large, the peak voltage of the switching device is low and switching loss is small. Therefore, the ZVS commutation circuit can be easily composed because it does not need to be of low inductance. These results show that a large-capacity drive system can be easily achieved with the proposed inverter.

Basic Studies for Accurate Commutation Analysis which Enables Commutation Spark Energy Estimation

DC machine has been used in steel industries and paper industries, Owing to their advantages for adjustable speed drive. The design objective for DC machines is to increase their output power and decrease their size and weight, though DC machines have more than 100 years of application history. Commutation is one of the most important for phenomenon which determines machine reliability, when the design objective is required in design stage. In other words, the commutation is an armature coil current reversing process, in commutation where the coil is short circuited by brush. In this paper the “Equivalent commutation circuit which is well known is applied to analyze the commutation process in this field. If the reversing process is retarded commutation spark may accrue at leaving edge of the brush and commutation failure may be caused.

Integrated auxiliary commutation circuits: a generalised approach

The concept of integrated auxiliary commutation circuits (iACCs) applied to systems with several power conversion stages is proposed. This concept has two main objectives, namely: to reduce the number of additional elements to accomplish the soft-switching and to use the circulating energy from one commutation to assist another one, so that the efficiency is improved without penalising the cost of the system. Some rules to obtain new iACCs are presented. New iZVT circuits are applied to a double-conversion UPS to illustrate the functionality and applicability of this concept. By using these circuits, the main switches operate under soft-commutation of ZVT type, and the auxiliary switches are turned on and off under ZCS or ZVS. Experimental results of three prototypes (1.2 kW at 100 kHz) are presented to demonstrate the good performance of the new integrated ZVT ACC and the feasibility of the proposed concept.

転流回路に用いる平型GTOのターンオン局部損失低減の一手法

In this paper, we present a design method for reducing local losses in a Gate Turn-Off Thyristor (GTO) at turn-on and protecting GTOs, particularly those of the flat-package type used in the high-frequency switching from overheating failure. This method utilizes the measurement of cathode-current spread obtained by infrared measurement. The performance of this was verified observing the gate-current at turn-on in a GTO used in the LC resonant commutation circuit for a power supply rated 10kHz, 1.0MW.

Electrode commutation sequence for honeycomb arrangement of electrodes in electrochemotherapy and corresponding electric field distribution

Electrochemotherapy is a treatment based on combination of chemotherapeutic drug and electroporation. It is used in clinics for treatment of solid tumours. For electrochemotherapy of larger tumours multiple needle electrodes were already suggested. We developed and tested electrode commutation circuit, which controls up to 19 electrodes independently. Each electrode can be in one of three possible states: on positive or negative potential or in the state of high impedance. In addition, we tested a pulse sequence using seven electrodes for which we also calculated electric field distribution in tumour tissue by means of finite-elements method. Electrochemotherapy, performed by multiple needle electrodes and tested pulse sequence on large subcutaneous murine tumour model resulted in tumour growth delay and 57% complete responses, thus demonstrating that the tested electrode commutation sequence is efficient.

Design of an Impulse Commutation Bridge for the Solid-State Transfer Switch

Voltage sags have become a very critical power quality issue in recent years. In particular, in the high-tech industry parks of Taiwan, manufacturers can lose up to one million U.S. dollars for each voltage sag event. Some utility companies provide dual power feeders to these high-tech manufacturers to enhance power quality and reliability. The solid-state transfer switch (STS) based on thyristors can thus utilize the dual power feeders to protect sensitive loads against voltage sags. Conventional STS often requires more than a quarter cycle to complete the transfer process because its commutation is load dependent. An improved STS with impulse commutated circuit can greatly reduce the transfer time and provide better ride-through capability against voltage sags. In this paper, an impulse commutation bridge STS (ICBSTS) system is proposed to further simplify the forced-commutation circuitry. This paper also discusses the in-rush phenomenon of the transformer due to the line transfer. A flux estimator is developed with the ICBSTS system to reduce the in-rush current.

A zero-voltage transition for three-phase double-PWM voltage-fed converter

In comparison with several zero-voltage transition (ZVT) inverter topologies, a double-PWM converter is presented using a simple ZVT topology. The rectifier and inverter of this double-PWM share a set of commutation circuit which can provide soft-switching for the power devices and the diodes. The commutation circuit consists of 1 auxiliary device, 6 resonant inductors, and 12 diodes. Its topology is simpler than the conventional auxiliary resonant converter, leading to low loss and easy control. The control strategy and resonant working modes are analyzed. Experimental results show good performance of the system.

In Memoriam: William McMurray

The career and contributions of William McMurray are recounted. One of the founding fathers of power electronics, he was world renowned for his invention of the McMurray inverter as well as the McMurray-Bedford inverter and other snubber and commutation circuits.

Analysis and Design of a New High-Efficiency Bidirectional Integrated ZVT PWM Converter for DC-Bus and Battery-Bank Interface

This paper proposes a high-efficiency bidirectional integrated zero-voltage transition (iZVT) pulsewidth-modulation (PWM) converter for dc-bus and battery-bank interface. The proposed converter can operate as battery charger when the utility is within its acceptable voltage range and can supply energy to critical loads when the utility fails. The converter practically eliminates both low- and high-frequency current ripple on the batteries, thus maximizing battery life without penalizing the volume of the converter. Moreover, soft switching of all switches is achieved using the proposed integrated auxiliary commutation circuit (iACC). Just one iACC is used to provide soft-switching conditions for the three converters that compose the system: the preregulator (boost), the battery charger (bidirectional converter operating as a buck), and the backup converter (bidirectional converter operating as a boost). This auxiliary circuit has few components and low reactive energy, increasing the system's overall efficiency. Experimental results based on a 580-W prototype are presented to validate the analysis and the proposed design procedure and to demonstrate the performance of the proposed approach

Characteristics of Arc-Reducing Effect by Capacitor in Commutation Circuit

DC motors are indispensable to improve the automotive functions. Recently, 70-100 motors are installed on luxury cars and this number is increasing year by year. With the recent demand for improved fuel economy and better equipment layout, the improvement of the motor's efficiency and the minimization of the motor size are the key to enhancing the competitive edge of the products. Adopting the high-density coil is an effective method for that, but it is accompanied by the commutation inductance rise which causes the commutation arc increase. The increase of commutation arc decreases motor life, because it causes the rise of brush/commutator wear. This report describes an arc-reducing effect obtained when capacitors are built into a commutation circuit for the purpose of reducing arcing under high commutation inductance conditions. The results of an evaluation using a equivalent commutation circuit and carbon brush/carbon flat-commutator showed that although a commutation circuit with built-in capacitor generated the same arc energy as a commutation circuit without a capacitor above a certain value of residual current, it displayed an excellent arc-reducing effect below that value of residual current.