Variable Frequency Drive Research Articles

Experimental studies on photovoltaic-thermal heat pump water heaters using variable frequency drive compressors

The present work attempts to devise an efficient method utilizing an on-grid photovoltaic-thermal heat pump water heater (PV-THPWH) integrated with a real-time variable frequency controller to achieve the goal of energy-efficient buildings. The prime focus is to reduce the grid's dependence on the compressor's energy-intensive operation by employing a feedback-controlled variable frequency drive (VFD). Additionally, the possibilities involved with addressing the electrical and thermal energy requirements of an energy-efficient building was investigated utilizing the proposed system. R-32 refrigerant in the photovoltaic-thermal (PV-T) evaporator coils of the heat pump assembly help to cool the photovoltaic (PV) panel while delivering the absorbed heat in the condenser to heat water contained inside the storage tank. Outdoor experiments and theoretical investigations of the combined system were carried out to appraise the dynamic behavior under varying solar irradiation and ambient temperature conditions. The observations conveyed that the PV-THPWH system succeeded in reducing the PV panel operating temperature by 25%, which resulted in a 20% increment in PV power output. Also, the performance indicators, such as the instantaneous energy efficiency and instantaneous PV efficiency, were found to increase by 15% and 34%, respectively, resulting in an average coefficient of performance of 6.4. For a clear sky day, the recorded total PV energy output was 4.67 units, while the VFD compressor consumption was 3.42 units, and the surplus 1.25 units were sent to the grid. Furthermore, the economic analysis reported a payback period of 2.3 years for the developed PV-THPWH system.

Analysis of the implementation of three-phase Variable Frequency Drive on the prototype of a rice drying machine

The prototype of the rice drying machine is a device used for rice dryers that are not weather dependent. The driver of this prototype rice drying machine uses ½ HP induction motor as its main mover. To be able to adjust the rotation of the induction motor using Variable Frequency Drive (VFD) brand LS iC5 with 1 HP power. The rotation needed to rotate the load can be done by changing the frequency and voltage so that the rotation speed of the induction motor can be adjusted as needed. From the testing of a no-load induction motor with a frequency adjustment range from 5 Hz to 13 Hz, the induction motor speed is 142.8 rpm (rotation per minute) to 375.3 rpm. The measured voltage is 76.5 V to 116.7 V and the measured current is 2.5 A to 1.6 A. From the results of the test of a no-load induction motor it can be concluded that the ratio of frequency to voltage is directly proportional while the ratio of frequency to current is inversely proportional. In testing induction motors with a frequency adjustment range from 5 Hz to 9 Hz, they produce the same conclusions as to the induction motor load testing. VFD is certainly appropriate to be used as a speed regulator as needed.

Studying the Influence of Connecting New Energy Saving Loads on the Electrical Power System of Nuclear Facility

Electrical system of nuclear facility should have suitable safety mechanisms and minimum losses for providing reliability of power supply to guarantee the continuity of operation. The purpose of having electrical infrastructure with high efficiency is to have energy delivery systems with high efficiency. So in this research, a proposed model of the nuclear reactor electrical system will be presented to study the effect of connecting new energy saving loads and advanced controllers on the system performance in order to keep safe and good performance of this nuclear facility. By using Electrical Transient Analysis Program (ETAP) software the NRR simulation model was developed. The analysis was performed with using nonlinear energy saving lighting systems and Variable Frequency Drive (VFD) installed as a controlled for secondary pump of the reactor by providing smooth motor starting also its advantage for energy saving. From the results, active power consumed and current were reduced, while VTHD and ITHD increase clearly. Finally the influences of using large number of LED (Light Emitting Diode) lamps and VFDs on the power quality were observed but not exceed the IEEE standard limits. Also, its impact on energy savings and economic benefits with safe and reliable operation was achieved.

Optimization of VFD Operations for Transporting Equipment of Packages

This study is focused on the efficiency of automated transferring system of packages equipped by variable-frequency drive (VFD) and servo drive motor. It was found that rotation frequency of induction motors and linear speed of servo drive decisively affected the unit efficiency that operates in the periodic mode. The system duty cycle was divided in two separate parts taking into account time spans needed to complete the specific tasks by each separate equipment of the system. In order to reduce the power usage of the system, the duration of each part of cycle was extended. Lowered electricity consumption leads to the extension of each cycle’s stage operating times. Frequencies of motors and linear speed of servo drive motors were optimized depending on cycle stages duration. Optimized frequency and linear speed values were calculated and loaded into motors controllers, and the efficiency of each separate equipment was measured, as well as total efficiency of the system. Experimental system debugging using optimized parameters proved that system efficiency increases up to 60 %, and that is closely matched with calculated values.

The Ultra-Compact ELF Magneto-Mechanical Transmission Antenna With the Speed Modulated EM Signal Based on Three-Phase Induction Motor

An extremely low-frequency (ELF) magnetomechanical antenna with the size of one-millionth wavelength based on a three-phase induction motor is reported, whose working frequency is no longer limited by the resonant wavelength. The rotating three-phase induction motor with nonmagnetic material shell is just equivalent to a rotating magnetic dipole with 1.5 times magnetic dipole moment. It can transmit the modulated electromagnetic (EM) signal by modulating the rotating speed of the motor. A near-field ELF EM signal transmission experiment system is constructed based on the magnetomechanical antenna with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi 10$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times50$ </tex-math></inline-formula> cm size, and the transmitted EM signals were received by a 200-turn coil, which is 10–200 m far away from the transmitter. The EM signal frequency is almost the same as the rotating speed of the motor, and it varies with the rotating speed too. With arbitrary waveform generator and variable-frequency drive (VFD) modulating the rotating speed of the motor, a near-field ELF transmitter with modulating EM signal is built, and the sawtooth wave (STW)-modulated EM signal was transmitted and received clearly during 10–200 m. The square wave (SW)-modulated EM signal was communicated too. The proposed magnetomechanical antenna has a compact size and is very suitable for ELF remote wireless communication.

New spinning technology for producing square section die-less spun parts in the sheet metal forming process

Sheet metal spinning is one of the main forming processes, being characterized by flexibility, low cost, reduced manufacturing time, and high formability. Where a flat metal blank is rotated at a high speed and this spun part is formed by pressing a forming tool into the blank, however, this process is limited to axisymmetric parts. This research thus aimed to design and build a simple and flexible mechanism for producing asymmetrical spun parts to allow non-circular forms (polygons) to be formed without interrupting the rotation of the turned blank, being synchronized with the rotation of the special forming tool. The proposed mechanism is based on developing a synchronous spinning machine in which the rotational motion and traditional lathe machine feed are monitored to maintain synchronization with the tool rollers (special forming tool), where the latter controlled by electric motors. The speed of the electric motors is controlled by a variable frequency drive (VFD), pulse-controls and specialized software. The proposed machine can be applied to multiple product shapes by changing the pulse-control in the software code, making the machine much more flexible than other options. Square cross-section parts were formed by cutting aluminum alloy sheets (1050) into a circular shape of 1.5 mm in thickness and 150 mm diameter. The experimental study then examined the effects of various process parameters on the spinning process, spindle speed of the lathe, feed ratio, and forming tool diameter. Three values were adopted for the three parameters, spindle speeds of 48, 68, and 135 RPM, feed ratios of 0.16, 0.22 and 0.32 mm/rev, and forming tool ball diameters of 16, 22, and 25 mm. The results showed that the maximum average in wall thickness reduction was about 27.44 %, and the maximum average error in dimensional accuracy was 6.47 % for spun parts made with a 45 mm mandrel.

Design and Implementation of Constant Speed control System for the Induction motors Using Programmable logic Controller (PLC) and Variable Frequency Derive (VFD)

This paper presents an automatic speed control system on three phase squirrel cage induction motor using Programming Logic Circuit (PLC) and Variable Frequency Drive (VFD) techniques. The aim of this study is to obtain a constant speed of induction motors when these motors are exposed to variable loads. The required speed of the induction motor can be set as a numerical value by (PLC), while the actual speed of the induction motor can be measured by a tachometer which is equipped with (PLC) ) Through an Analog to Digital Converter (ADC). Then the two speeds are compared to the set point with minimum error to get the required constant speed. The control system designed to be tested with two stator poles number (two and four poles) of induction motors. The results have cleared that in spite of doubled the load 11 and 8 times respectively, but the yield average shaft speeds are almost constant 2891.15 rpm and 1402.45 rpm respectively.

An Industrial Survey on Electric Drives and Scope of Multilevel Inverter Based Induction Motor Drives in Sugar Industry

A typical sugar industry has electric motors ranging from a few kW to a few MW. For controlled speed–torque characteristics, at most of the places, variable frequency drives (VFDs) are used. DC drives are also used in place of VFDs at milling and batch type centrifugal machines. Slip ring induction motor (SRIM) drives are invariably used at sugarcane preparation station and also at some large pump and fan loads of the industry. At many places, the type and configuration of electric drives need to be reviewed keeping in view the recent developments in the area and improvements in similar applications in other industries. There is also a need to review the aspect of efficiency and harmonics associated with these conventional electric drives in the industry. Further, the VFDs, wherever installed in the sugar industry, are, invariably, 2-level inverter-based induction motor drives. The potential of the multilevel inverter (MLI)-based induction motor drives, being improved one, also needs to be explored in the industry. This paper presents a survey on types of electric drives presently being used for various applications in the sugar industry, their merits and demerits, further possible improvements in them for power saving and reduction in harmonics along with the potential of application of MLI-based induction motor drives, wherever feasible, in the industry.

Sensorless parameter estimation of VFD based cascade centrifugal pumping system using automatic pump curve adaption method

The Sustainable Development Goal 7 necessitates efficient energy utilization and aligning energy efficiency targets to industrial machines would pave a way for prospective developments. Pumps are inevitable in commercial and industrial sectors and they contribute to nearly 22% of the global industrial energy utilization. Attesting the fact, this paper focuses on the energy-efficient operation of a pumping system by governing the speed using Variable Frequency Drives (VFDs). This is accomplished by modeling the pump performance curves by estimating the parameters like flow rate and pressure values for automatic adaptation in VFDs. With the aid of the manufacturers’ datasheet and the operating state of the pump, the pump performance curve is estimated automatically. The pump operating point is attained from pump parameters and motor rotational speed without using the sensors (sensor-less). This proposed methodology is validated through an experimental setup with a 1.1 kW Induction motor (IM) based centrifugal pump driven by 2.2 kW Danfoss VFD and the obtained results can be adopted for estimating the operating point of the centrifugal pumps throughout its operating range. Further, the variations in accuracy between actual and measured flow rate for the proposed scheme is found to be ranging from −5.29 GPM to 2.03 GPM which is about −0.243% to 0.0713%. Specifically, the pump flow rate estimation accuracy deviation is found to be between 2%–8% during lower operating flow rates and is within 2% during the higher operating region. Further, the proposed scheme offers better efficiency than the conventional sensor-based method which constitutes about 2% deviation in accuracy. Consequently, it empowers Industrial users to perform energy-efficient optimization for the cascade pumping system.

Examination of Composite Load and Variable Frequency Drive Air Conditioning Modeling on FIDVR

Fault induced delayed voltage recovery (FIDVR) is a credible concern in power systems with high penetration of single-phase air conditioner loads. Power system planning studies use dynamic load models, such as the Western Electricity Coordinating Council (WECC) composite load model CMPLDW to examine FIDVR in power systems. The behavior of modern variable frequency drive (VFD) air conditioners to voltage drops is not the same as traditional one- or two-speed air conditioning systems. This paper investigates the impact of increasing VFD air conditioner penetration within a power system on FIDVR events, by first modeling VFD air conditioners as a separate load and then as a power electronic component within the CMPLDW model. Simulation results show that increasing the penetration of VFD driven air conditioners decreases the post-fault voltage sag, recovery time, and number of customers interrupted by undervoltage load shedding.

Fault Diagnosis for Variable Frequency Drive-Fed Induction Motors Using Wavelet Packet Decomposition and Greedy-Gradient Max-Cut Learning

In this paper, a novel fault diagnosis method for variable frequency drive (VFD)-fed induction motors is proposed using Wavelet Packet Decomposition (WPD) and greedy-gradient max-cut (GGMC) learning algorithm. The proposed method is developed using experimental stator current data in the lab for two 0.25 HP induction motors fed by a VFD, subjected to healthy and faulty cases under various operating frequencies and motor loadings. The features are extracted from stator current signals using WPD by evaluating energy eigenvalues and feature coefficients at decomposition levels. The proposed method is validated by comparing with other graph-based semi-supervised learning (GSSL) algorithms, local and global consistency (LGC) and Gaussian field and harmonic function (GFHF). To enable fault diagnosis for untested motor operating conditions, mathematical equations to calculate features for untested cases are developed through surface fitting using features extracted from tested cases.

Thermal Characterization of SiC Modules for Variable Frequency Drives

Silicon carbide (SiC) devices can exhibit simultaneously high electro-thermal conductivity and extremely fast switching. To perform optimal designs showing the benefits of SiC in achieving efficiency, size, weight, and cost objectives for electric converters design, it is necessary to establish better models for calculating device losses and an efficient thermal model that can be calibrated to consider the nuances of measurement based thermal equivalent circuits. This work's outputs can be used in a power converter multi-objective optimization process or real-time temperature prediction of drives to improve reliability and maximize performance. The proposed modified loss calculation and thermal model demonstrate the SiC power module's advantages to reduce peak junction temperature and power cycling effects. A detailed power loss calculation and thermal model is developed and tested on a 480 V, 186 A, 150 HP variable frequency drive (VFD) with SiC modules. A comparison between the SiC module and an equivalent rated Si module demonstrates the reduction in power cycling effects, particularly at low-speed operation. Infrared (IR) imaging results and analytical explanations of the phenomenon is provided. Power cycle tests show that higher thermal conductivity is not the only reason contributing to the lower temperature ripple in low-speed operation.

Modeling of Alternating Current Motor Performance for Increased Production Using Fuzzy Logic Controller

The low productivity experienced in our industries is as a result of not imbibing intelligence in its production mechanism. We know that induction motors are reliable, robust and with good operating characteristics. A means of starting, regulating and controlling operating parameters are very necessary to improve motor efficiency. This low productivity witnessed in our brewery industry is surmounted by modeling of alternating current (a.c) motor performance for increased production output using fuzzy logic controller. To achieve this it is done in this manner, characterizing and modeling a conventional AC motor so as to establish its operational features while working on variable frequency drive (VFD) control model with known production output, designing a rule base for the use of fuzzy controller for a stable and improved production output of AC motor and designing SIMULINK model for the performance of AC motor under operational condition for an increased output using fuzzy controller for a brewery industry. The results obtained are the highest conventional quantity of bottles of beer produced was 3240 while that of fuzzy controller was 3245 at a stable time of 4 through 10 seconds. With these results obtained, it shows there is an improvement in the production capacity in brewery industry when fuzzy controller is incorporated in the system.

Technico-Economic Study of a Photovoltaic Pumping System Using a Variable-Frequency Drive Converter

This paper presents a technical-economic study of a photovoltaic pumping system using an inverter with a Variable Frequency Drive (VFD) to improve system efficiency. We propose a comparative study between two pumping station projects located in places very close to each other, in order to consider that they are exposed to the same meteorological data. One of the projects has the maximum power tracking technique (MPPT), while the other project does not have this technique. The study will compare the various experimental surveys carried out in the field with modeling results using Matlab Simulink.

Integrated green submersible pumping system for future generation

In the system solar power has been used for cultivation. Solar photovoltaic cells convert solar energy into electricity through solar photovoltaic (SPV) effect. Generated DC voltage then converted in to AC voltage by pump controller, this AC voltage is used as the input of Variable Frequency Drive (VFD). The VFD acts as a motor controller that controls the submersible pump motor by varying the frequency and voltage of its input power supply. The VFD is associated with pump controller. Regulated three phase AC voltage is the output of the pump controller which is directly connected with submersible pump. The water thus drawn from bore wells by a solar water pump is pumped to supply for irrigation purpose as required. This system is full off-grid interfaced system appropriate for the village areas. The main goal of this system is to use solar energy at a minimum running cost. The solar powered project is completely eco friendly and the plant is relatively clean with small maintenance. This project helps to reduce the cost of electricity, as well as minimize the overall agricultural cost.

Heat transfer studies at different speeds and loads of regenerative air preheater in thermal power plant

Regenerative air preheater is one of the largest heat recovery systems in thermal power plants. There are various factors, which determine the heat transfer rate in regenerative air preheaters (RAPH) such as, material of heating elements, temperature difference between air and flue gas, quantity of flue gas, amount of air passing through the RAPH and its rotational speed. In all power plants, RAPH is designed to operate at constant speed where the maximum heat transfer is achieved in full load operation. The rate of heat transferred to the air is compared at different loads and speeds of the RAPH and the optimum speed at which maximum heat transfer rate occurs is found in this experimental study. Speed is varied using a Variable Frequency Drive (VFD) power supply to the RAPH motors. Based on the study, it is inferred that the optimum speed varies with load of the power plant. A cost benefit analysis is also carried out, which clearly indicates that more amount of energy could be conserved by operating the RAPH at various speeds rather than at constant speed.

Dynamic torque response improvement of direct torque controlled induction motor

Induction motor is extensively being used with variable frequency drive (VFD) in variable speed service. Direct Torque control (DTC) of induction machines is simple compared to the Field oriented control (FOC). Although DTC has advantages there are some disadvantages like torque ripple is high, switching frequency is variable. This paper proposes a dynamic over modulation strategy which can be implemented in DTC to improve the dynamic response and to reduce the torque ripple. The objectives are achieved by switching voltage vector that produces the most tangential component to the circular flux locus. The principle advantage of the proposed technique is its effortlessness, since it requires a minor change to the conventional DTC-hysteresis-based structure. 80% reduction in torque ripple and 40% improvement in dynamic response are achieved in the proposed method compared to conventional method.

Motor side active power filter for induction motor

Power quality is an important aspect in electrical distribution and utilization systems. Variable frequency drive (VFD) controlled induction motors are widely used in industries. The output current of VFD which is nonsinusoidal is given to the induction motor. This paper proposes a motor side active power filter (MSAPF) so as to provide a pure sinusoidal current to the induction motor. An evaluation of two control strategies has been discussed in this paper i.e. Synchronous Reference Frame (SRF) theory and Instantaneous Reactive Power theory (IRPT) in the generation of the reference signal. These techniques are simulated in MATLAB/SIMULINK environment. These simulations demonstrate the reduction in total harmonic distortion (THD) in the motor current with active filter connected to the motor side.

A Novel Solution to Eliminate Frequency Intermittency by Adding Spinning Reserve to the Micro-Hydro Turbine Generator using Real-Time Control of Induction Motor through AC-DC-AC Power Converters

Small micro-hydro has a variable output in terms of frequency and voltage. Formerly Electronic Load Controller has been used to stabilize the output frequency of micro-hydro in which these ELCs wasted extra generated energy as heat. In this paper, a novel approach to handle these frequency variations by designing a Variable Frequency Drive (VFD) is proposed. Besides, the electronic governor of micro-hydro turbine generator is designed by incorporating a variable speed induction motor. Thus, the spinning reserve of the motor could be used for irrigation or water storage purposes by consuming extra generated power. Further, the DC bus of VFD enables the system to integrate with other Distributed Energy Sources (DES), which will be helpful in the future extension of the microgrid.

Performance Enhancement of Line Start Permanent Magnet Synchronous Motor With a Special Consequent Pole Rotor

This paper presents the development of line start permanent magnet synchronous motor (LSPMSM) employing a special consequent pole rotor. The proposed rotor structure uses both circumferentially magnetized spoke shape and radially magnetized arc shape magnets. The combination of spoke and arc shape is arranged to provide consequent magnetic poles. This new rotor structure improves the motor performance and consumes less magnet volume. The time-stepping finite element analysis (FEA) is used to evaluate transient and steady state performances. Extensive simulation studies are performed to establish the supremacy of proposed rotor structure over benchmarked spoke and some other known rotor structures. For experimental validation, prototypes of machine are built using (a) proposed magnet configuration, and (b) spoke type configuration having circumferentially magnetized magnets which is used as baseline motor. Rigorous experimental studies are carried out and it is observed that the proposed structure offers 4% improvement in the full load efficiency over the benchmarked spoke rotor LSPMSM yet by saving 10% magnet volume. Further, it is observed that the performance of the proposed machine is enhanced for direct online (DOL) as well as variable frequency drive (VFD) fed supply operation.