Wide Power Range Research Articles

회전속도와 간극 폭에 따른 모터의 열전달 특성에 대한 수치적 연구

Three-dimensional computations are performed to investigate the flow and thermal characteristics of a synchronous reluctance motor, which is capable of wide range of constant power and variable speed operation required for industrial applications such as control devices. This work focuses on the effects of rotational speed and rotor-stator gap width on the flow and thermal characteristics. The present computations show that thermal generation and convection changes with rotational speed have a significant effect on the motor temperature distribution, and that the flow and temperature fields in the rotor-stator gap strongly depends on the rotational speed and gap width relative the critical conditions. The heat transfer path in the motor is comparatively analyzed according to the rotational speed and rotor-stator gap.

Compact and efficient wideband rectifier based on π network with wide input power ranges for energy harvesting

This work introduces a wideband, significant RF-DC conversion efficiency and large DC voltage radio frequency (RF) voltagemultiplier/doubler rectifier for energy harvesting (EH) systems utilizing ROG4003C material and Schottky diode. The input matching network is designed using π network and series resonance circuit. Two wideband rectifiers are designed the first one uses lumped inductors in the π network, and the second design employs distributed rectangular inductors. The π network is connected in series with a Schottky diode to compensate its capacitive reactance, diminish its impedance variation when the frequency or input power varies while the series resonance circuit is used to match the minimized variance to the source impedance (50 Ω). An HSMS2852-based rectifier prototype is tested for verification, obtaining a bandwidth of 31.6 % from 720 to 1050 MHz with 68 ± 2 % at an input power of 3 dBm with a peak saturated DC voltage of 3.6 V and an input return loss (S11) less than −10 dB.The proposed rectifiers provide good performance over a wide input power range between −10 dBm and 5 dBm via various load terminals ranging from 2.5Kohms to 10Kohms. The proposed rectifier is suitable for GSM 900, IoT, UHF ISM 900 MHz, WSN, broadband LTE, and multi-standard systems. Finally, the introduced voltage doublers have a compacted area equal to 1.85 cm2.

Efficient Power Coupling in Directly Connected Photovoltaic‐Battery Module

Due to the intermittent nature of solar irradiance and the temporal mismatch between solar power generation and consumption profiles, the combination of photovoltaic (PV) devices with energy storage is essential. The maximum power point tracking (MPPT) devices are commonly used for the connection of PV to electrochemical storage and load, ensuring power matching and providing flexibility in system design. Herein, the usability of direct PV‐battery coupling as an alternative to MPPT under realistically varied battery state of charge (SoC), irradiance, temperature of the PV module, and applied load is investigated. A stable power coupling factor above 90% is demonstrated between a silicon heterojunction solar module and Li‐ion battery in the whole range of measured SoC (12.5–75%) and a wide range of load power. The dependence of power coupling on temperature and irradiance is calculated and compared to the power generation profile of a PV plant installed in southern Germany. In the region of highest power generation, the direct connection provides coupling efficiencies above 95%, reaching 100%, for the usable range of battery SoC. These results show that direct PV‐to‐battery coupling is feasible for a variety of practical applications and scales.

Self-adaptive passive temperature management for silicon chips based on near-field thermal radiation

Temperature management in modern instruments is often a great task, particularly for silicon chip technologies against the background of the ever-increasing demanding for larger scale and higher density electronics integration. Enormous efforts have been made to solve this long-pending issue, mostly relying on active equipment that consume more energy and more space. Here, a compact thermal management technique for silicon chips is proposed, which is able to passively maintain the operation temperature of targets within a wide range of input power. The core part is a self-adaptive near-field thermal radiation system made of a phase-changeable metasurface and graphene/hBN heterostructure with surface plasmon/phonon modes. Numerically, we show that integrated with such a setup, a 0.1-mm thick silicon substrate could automatically maintain its operation temperature within a narrow window (∼333 ± 7 K) when loaded with heat power varied in 0.1–1 W cm−2. As a comparison, the temperature will change 614 or 319 K for a bare or blackbody-coated silicon substrate. The dynamic process of thermal homeostasis is discussed by using the transient thermal equation. The results imply that the current design is suitable for providing a compact, conformal thermal functional coat to passively manage temperatures of heated electronic components, particularly in vacuum.

Design of multi-channel AlGaN/GaN Schottky diode for improving rectification efficiency in microwave power transmission

Schottky barrier diode (SBD) is the core of the rectification circuit in the microwave power transmission (MPT) system and suitable for high-power RF-DC conversion. However, the rectification efficiency of current commercial SBD cannot meet the requirements of the MPT system. Therefore, this paper proposes a microwave rectification circuit based on the multi-channel AlGaN/GaN SBD. The effect of diode parameters on the rectification efficiency has been investigated, such as the number of channels, the length of anode field plate (LAFP) and the thickness of insulation layer. Simulation results show that multiple AlGaN/GaN heterojunctions can significantly reduce the on-resistance of SBD and improve the rectification efficiency. The power capacity of SBD can be increased withthe optimised LAFP and the thickness of insulation layer, which enables efficient microwave rectification in high power applications. High RF-DC rectification efficiency of 85.1% is obtained at the input power of 33 dBm. The rectification efficiency exceeds 60% over a wide input power range (14–38 dBm). The results demonstrate the great potential of multi-channel AlGaN/GaN SBD for high-power MPT application.

−11 to 7 dBm Power Range, Triple Band RF Energy Harvesting System With 99.9% Peak Tracking Efficiency and Improved PCE

This paper presents a triple-band radio frequency (RF) energy harvesting system with 99.99% peak tracking efficiency and the triple band rectifier achieves the 4.6% improvement in the power conversion efficiency (PCE). The proposed system has a power range of −11 to 7 dBm with the three bands targeted on 900, 1900, and 2400 MHz. In this paper, the voltage and power characteristics of the triple-band rectifier at each band are extracted as raw data by measurement. The DC-DC boost converter is applied to achieve the maximum power point tracking (MPPT), which exploits the hill-climbing MPPT method. The method is implemented with register logics and power calculator. The converter’s voltage range of 0.1V to 2V is achieved, and the converter facilitates to achieve the highest tracking efficiency of 99.99%, 98.57%, 99.85% at each bands. The performance is verified through experimental results showing PCE improvement and over 87% tracking efficiency in a wide power range at triple bands. The triple-band rectifier with transmission line is fabricated on FR-4 substrate with active area 35.7 cm2, and the DC-DC boost converter with MPPT is implemented in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> CMOS process with an active area of 0.94 mm2.

A Robust Capacitor Voltage Balancing Method for CPS-PWM-Based Modular Multilevel Converters Accommodating Wide Power Range

Capacitor voltage balancing is one of the most important issues for the safe, reliable, and economical operation of the modular multilevel converter (MMC). This article proposes a modified individual capacitor voltage balancing method for MMCs with phase-shifted carrier pulsewidth modulation (PWM) (CPS-PWM) to solve the problem of the poor dynamic performance that the conventional individual voltage balancing methods suffer at low output power. In the proposed method, the information of arm current is incorporated into the balancing algorithm to cancel out the coupling effect of the output power on balancing control. Compared with conventional balancing methods, the proposed method shows better robustness against varying output power and maintains a good dynamic performance in a wider power range. The complete modeling process and parameter design are presented and considered for system stability. The effectiveness of the proposed method is verified with both MATLAB/Simulink simulation and experimental results.

Accelerating High-Fidelity Thermal Process Simulation of Laser Powder Bed Fusion via the Computational Fluid Dynamics Imposed Finite Element Method (CIFEM)

• A finite element (FE) method is proposed to accelerate high-fidelity scanwise thermal process simulation in laser powder bed fusion (L-PBF) • Computational fluid dynamics (CFD) thermal fields are predicted by a dimensionality reduction based deep learning framework • Predicted thermal fields are imposed on the finite element (FE) solution domain within a relatively small region encompassing the melt pool, while heat diffusion effects elsewhere are solved via the FE method • The FE solution precisely matches the CFD solution across all melting regimes • The FE model running on a GPU card with 4,608 CUDA cores is 28.2x more efficient than the CFD simulations running on 24 CPU cores in parallel The current work proposes a finite element method (FEM) to accelerate scanwise thermal process simulation of the laser powder bed fusion (L-PBF) process with computational fluid dynamics (CFD) resolution near the melt pool. Termed the CFD imposed FEM (CIFEM), the transient thermal fields from a high-fidelity CFD simulation and inferred by deep learning are imposed as temperature values rather than utilizing a conventional heat source model as in existing FEM-based process simulations. These fields are enforced only within a relatively small computational region encompassing the melt pool, while heat diffusion effects elsewhere are solved via the FEM. For a wide range of laser power and scan speeds covering the conduction, transition, and keyhole melting regimes, 29 of the 30 total CIFEM-simulated melt pool sizes lie within two standard deviations of the experimental melt pool sizes. Compared with the CFD simulations, the thermal fields obtained by CIFEM possess 7.44% mean absolute relative error (MARE), significantly less than the 43.76% MARE on three representative test cases simulated using the Goldak heat source model calibrated to the measured melt pool dimensions. In terms of computational efficiency, the CIFEM model running on a GPU card with 4,608 Compute Unified Device Architecture (CUDA) cores is 28.2x more efficient than the CFD simulations running on 24 CPU cores in parallel.

Estimation of Harvested RF Energy Based on Survey of Ambient RF Power for Optimized Rectifier Design

This paper presents estimation of harvested RF energy by means of measurement survey and rectifier circuit simulation. The survey was done in an indoor environment in Bangkok, Thailand using a low-cost in-house developed measurement system. From the survey, channel power distribution of a signal with 950 MHz center frequency and 20 MHz bandwidth was created. The maximum time averaged channel power is -7.6 dBm whereas the mean value with maximum signal statistic is -11.1 dBm. A single stage rectifier is simulated with 5 different nominal values of RF input power which is used to optimize the rectifier for maximum RF-to-DC power conversion efficiency. The rectifier composes a Schottky diode, a matching network and a simple load consisting of a resistor and a storage capacitor. Parameters of the simplified LC matching network have been varied to match the rectifier’s input impedance to 50 Ω for various nominal values of the RF input power. In addition, the load resistance was varied according to the nominal RF input power for an optimal power conversion efficiency of the rectifier. The rectifier delivers the highest harvested RF energy with a nominal RF input power of -9 dBm which is a value between the maximum and the mean values from the survey. The DC energy converted from ambient RF energy by the rectifier can be estimated. With this information, it can be assessed what type of applications based on available RF energy can be applied for the test area. This rectifier optimization strategy can be applied to any kind of RF signal since it is based on actual measurement results. Moreover, the proposed rectifier can be designed for reconfigurability regarding nominal RF input power at the location of interest by varying the matching network parameters and the load resistance. In practical applications, the reconfigurable rectifier can maintain a high level of power conversion efficiency over a wide range of RF input power. This can be done by optimizing the rectifier’s input matching network and the load resistance for the highest possible power harvested from the environment where the rectifier is located.

Design of a metal-based deformable mirror for orthogonal beam deflection and highly dynamic beam oscillation.

We report on an opto-mechanical metal mirror design for highly dynamic, diffraction-limited focus shifting. Here, the mechanical geometry of the membrane is of crucial interest as it must provide sufficient optical performance to allow for diffraction limited focussing and have a high mechanical eigenfrequency to provide dynamic motions. The approach is the analytical consideration of the plate theory and provides the basis for a parameterized finite element model. By means of an finite element analysis (FEA), essential steps for the optimization of the mirror design with respect to a wide range of optical power and a high operating frequency are shown. To verify the results of the FE analysis, the deformed surface is decomposed into Zernike coefficients. An analysis of the point spread function is performed to evaluate the optical performance. For dynamic evaluation a modal and a harmonic vibration analysis are conducted. The opto-mechanical design allows a biconical deformation of the mirror surface, enabling the generation of a diffraction-limited spot diameter in the adjustment range of ±1.2 dpt. The surface shape error in this range is 53 nm. The dynamic analysis shows the first excited eigenfrequency at 21.6 kHz and a diffraction-limited operation frequency at 9.5 kHz. This paper provides an alternative design approach for highly dynamic beam oscillation in the Z direction, forming a complement to highly dynamic X-Y scanning systems.

An Interleaved Soft Switched High Step-Up Boost Converter With High Power Density for Renewable Energy Applications

In this article, a novel soft switched interleaved boost structure with a simple auxiliary circuit is proposed which is suitable for stand-alone loads or ac grid applications. In this topology, coupled inductors and switched capacitor cells of parallel modules are merged to obtain high voltage conversion ratio. The converter also has the capability of adding extra switched capacitor cells to attain very high voltage gain. To provide soft-switching condition in the wide range of output power, a new zero-voltage transition auxiliary circuit is employed which is responsible for soft switching of both phases and benefits from low conduction losses, the minimum number of semiconductor elements, and only one auxiliary gate-driver. These merits provide very high efficiency at both full-load and light loads. More importantly, no auxiliary magnetic components are utilized by taking advantage of the leakage inductance of coupled inductors for the resonant network. All semiconductor components operate under soft switching alleviating the reverse recovery problem and switching losses. Besides, the converter benefits from common ground between input and output which simplify voltage feedback. The experimental results of the interleaved converter prototype with 400-V output voltage at 400 W and 100 kHz switching frequency are provided. The full load efficiency of 98% was achieved and the power density was observed 1.9 W/Cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

A High Voltage Gain ZVT Quasi-Z-Source Converter With Reduced Voltage Stress

In this article, a new high voltage gain quasi-Z-source (QZS) dc–dc converter suitable for renewable energy applications is presented. The proposed converter utilizes a zero voltage transition auxiliary circuit with coupled inductors to provide soft-switching conditions for all switches for a wide range of output power. In addition, a switched capacitor circuit is employed to obtain a higher voltage gain and lower voltage stress. The main advantages of the proposed converter include high voltage gain, high efficiency, reduced switch and diode voltage stress, continuous input current, and common ground between the output and input, which are important features for photovoltaic applications. In this circuit, the reverse recovery problem of diodes is alleviated. Operating principles and design considerations of the proposed converter are analyzed. Moreover, to prove the validity of the theoretical analysis, a 200-W prototype of the proposed converter is implemented and the experimental results are shown.

Multi-Mode Control of a Bidirectional Converter for Battery Energy Storage System

In this paper, a bidirectional converter with multi-mode control strategies is proposed for a battery energy storage system (BESS). This proposed converter, which is composed of a half-bridge-type dual-active-bridge (HBDAB) converter and an H-bridge inverter, is able to operate the BESS with different power conditions and achieve the DC–AC function for lower input DC voltage applications. For the HBDAB converter, the variable-frequency control (VFC) and phase-shift control (PSC) are both adopted to achieve zero-voltage switching over a wider power range and the battery module balance control capability for BESS, respectively. In addition, the interleaved configuration is used to reduce the current ripple and increase the overall current rating. For the H-bridge inverter, the unipolar control mode (UCM) and totem-pole control mode (TPCM) are adopted to manage the real and reactive current control under different AC grid conditions. The UCM offers a reduction in current ripple for real and reactive power control. The TPCM is able to eliminate switching losses and achieve higher conversion efficiency for pure real power control. Considering applications for battery energy storage systems, the principle of operation and voltage gain analysis are described. Finally, computer simulations and hardware experimental results from a prototype system are presented to verify the performance of the proposed converter with the different control strategies.

Design of a hexagonal slot rectenna for RF energy harvesting in Wi‐Fi / WLAN applications

This work proposes a single port hexagonal slotted rectenna operating at 2.45 GHz Wi-Fi bands, using a hexagonally slotted shape of microstrip radiator surface followed by a voltage rectifier circuit using Schottky diode. A symmetrically extended ground plane and rectangular slots help in obtaining the desired resonance characteristics with improved antenna bandwidth. Three different antenna designs have been compared and analyzed. Best gain and wide most bandwidth is seen in the newly designed rectangular and hexagonal slotted design having symmetrically extended ground plane. A RF capacitor and inductor based matching network has been designed to maximize the wireless power transmission at 2.45 GHz. This also helps to enhance the rectifier efficiency for various values of load resistance and input power. Furthermore, for maintaining the small size and ensuring least amount of energy loss, the rectifier's ground has been directly connected to the antenna's ground plane. The proposed design has been simulated in HFSS and ADS software, prototyped, and measured. It has been seen in the results that, the proposed radio frequency (RF) power receiving antenna is performing very well at 2.45 GHz with a wide bandwidth ranging from 1.25 to 2.63 GHz. The proposed rectenna is having a maximum efficiency of 62.4% at 2.45 GHz with an input power of 0 dBm. Furthermore, with variations in the load resistance across a wide range of values from 4 to 12 kΩ $$ \mathrm{k}\Omega $$ under a wide range of low input power, the rectenna maintains an efficient power conversion, which is found to be an important parameter when the ambient RF signal input to the antenna is weak. As a result, the rectenna may be adaptable to a variety of low-power electronic circuits by harvesting RF energy at 2.45 GHz Wi-Fi Band. Furthermore, the proposed antenna can also be used for wireless medical telemetry, satellite phone and Wi-Fi applications used for the frequency band 1.45 GHz as well.

Vibration energy harvesting for cars: semi-active piezo controllers

Energy harvesting represents one of the recent challenging subjects related to vibration and control. The scale of energy harvesters and storage can involve a wide power range, and the scale of some milliwatt is the elective field of piezoelectric applications. This paper investigates the power frontiers of the piezoelectric-based harvesters applied to automotive units. The analysis, supported by experimental data, aims at estimating the upper bound of the specific power of this technology for powering small devices on board cars. Passive optimally tuned piezoelectric harvester and semi-active controlled ones are compared, based on a new control strategy named VFC-Variational Feedback Control, recently developed by the authors. This new technique makes it possible to increase the total energy storage drained from car vibrations. However, the real advantage for their use relies on a sharp balance between the harvested power and the costs for the additional hardware mass transport. Numerical simulations of circuitry and experimental vibration data provides references to assess the energy convenience in installing this type of devices on board.

Non-Destructive Electromagnetic Evaluation of Material Degradation Due to Steel Cutting in a Fully Stacked Electrical Machine

Although it is well known that the magnetic properties of electrical steel can be deeply affected by the cutting process, it is still not clear how to accurately evaluate these effects on a prototyped machine on its final shape, especially at a high frequency or a high power rating. This research provides a more practical method for accurate measurement of magnetic losses in electrical steel with consideration of material degradation effects due to the cutting process. Unlike other similar studies, these investigations are conducted not only on a few laminations but also on a complete electrical machine core. For a fair comparison between both cases, backlack bonding is used for lamination stacking since it is the most non-damaging joining technique. Two different test setups are used to measure the steel performance at a wide range of frequency and input power. Furthermore, a full axial length stator of a switched reluctance machine (SRM) is used as a case study to identify the magnetic properties of NO20 electrical steel. Additionally, by comparing the results obtained from the individual laminations and the assembled stator, the extra losses due to the cutting process and material degradation are extracted accurately.

A review of conventional and new-generation aircraft starter/generators in perspective of electric drive applications

PurposeMore electric aircraft (MEA) is defined as the extensive usage of electric power in aircraft. The demand for electric power in new generation aircraft rises due to environmental and economic considerations. Hence, efficient and reliable starter/generators (SGs) are trending nowadays. The conventional main engine starting system and power generation system can be replaced with an individual SG. The constraints of the SG should be investigated to handle the aviation requirements. Even though the SG is basically an electric machine, it requires a multidisciplinary study consisting of electromagnetic, thermal and mechanical works to cope with aviation demands. This study aims to review conventional and new-generation aircraft SGs from the perspective of electric drive applications.Design/methodology/approachFirst of all, the importance of the MEA concept has been briefly explained. Also, the historical development and the need for higher electrical power in aircraft have been indicated quantitatively. Considering aviation requirements, the candidate electrical machines for aircraft SG have been determined by the method of scoring. Those machines are compared over 14 criteria, and the most predominant of them are specified as efficiency, power density, rotor thermal tolerance, high-speed capability and machine complexity. The features of the most suitable electrical machine are pointed out with data gathered from empirical studies. Finally, the trending technologies related to efficient SG design have been explained with numeric datasets.FindingsThe induction motor, switched reluctance motor and permanent magnet synchronous motor (PMSM) are selected as the candidate machines for SGs. It has been seen that the PMSM is the most preferable machine type due to its efficient operation in a wide range of constant power and speed. It is computationally proven that the using amorphous magnetic alloys in SG cores increases the machine efficiency more. Also, the benefits of high voltage direct current (HVDC) use in aircraft have been explained by a comparison of different aircraft power generation standards. It is concluded that the HVDC use in aircraft decreases total cable weight and increases aircraft operation efficiency. The thermal and mechanical tolerance of the SG is also vital. It has been stated that the liquid cooling techniques are suitable for SGs.Originality/valueThe demand for electrical power in new generation aircraft is increasing. The SG can be used effectively and efficiently instead of conventional systems. To define requirements, constraints and suggestions, this study investigates the SGs from the perspective of electric drive applications.

Numerical analysis of discharging stability of basalt fiber bundle thermal energy storage tank

In this paper, a new thermal energy storage (TES) scheme of basalt fiber bundles is proposed. This basalt fiber bundle TES tank adopts two-stage runner arrangement to increase the specific surface area and improve the heat exchange effect. Based on this, a variable flow rate and preheating control scheme is proposed to enhance the discharging stability. The results when the air initial flow rate is 1m/s show that the two methods of automatically controlling the flow rate change and using two tanks in series to make full use of the waste heat can significantly increase the stable discharging time of the TES tank. The increase in the stable discharging time reached 115% with variable flow rate scheme. And the simultaneous use of variable flow and preheating control schemes can extend the stable discharging time to 166% of the constant flow scheme. This TES tank can provide a wide heating power range and the maximum discharging power per unit area reaches 1.005MW±1% when the initial flow rate is 1m/s. However, it is difficult for honeycomb and packed bed to achieve such output under the same flow rate. In short, this new scheme can realize the coexistence of high thermal energy storage density, strong stable discharging, small volume and high discharging power, and can be used in mobile thermal energy storage system to meet user groups with significant differences in heating demand.

Mechanism investigation for the influence of laser power on droplet transfer behaviors in laser-MIG hybrid welding

The stability of droplet transfer plays an important role in the weld formation and spatters suppression during the laser-MIG hybrid welding. However, a debate exists on whether increased laser power improves or suppresses the droplet transfer. In this study, the role of laser heat source was investigated in a wide range of laser power. The transfer frequency was firstly improved by increasing laser power, and then it was decreased once the laser power proceeded a critical value. The variation of droplet transfer frequency was determined by the competition between electromagnetic force and metal vapor reaction force. With increasing laser power, the arc conductivity was better and the arc current was improved, leading to increase of the electromagnetic force. As a result, the droplet transfer was promoted and the deposition rate of wire metal was increased. However, rapid increase of metal vapor reaction force was obtained when the laser power exceeded the critical value, producing a greater resistance on droplet transfer. Furthermore, the critical value of laser power was mainly determined by the characteristics of laser source, materials, laser focusing distance and laser-arc distance. This work will provide more guidance on matching processing parameters of the laser-MIG hybrid welding to improve weld formation and suppress spatters by stabilizing the droplet transfer.

PROBABILITY DENSITY FUNCTION OF AVERAGE POWER OF REAL SPEECH SIGNALS

It is known that many real signals, such as speech signals, are non-stationary processes that express theirfeature through changes in parameters over time. By observing speech in shorter time intervals, the property ofstationarity can be notice. This characteristic enables the application of techniques for adaptation to local signalcharacteristics in signal processing algorithms. Many of these algorithms are described by standards, and in additionto intensive development in this area in last decades, there is a constant need for the development of new solutionsand standards. One of the most used parameters of the speech signal for adaptation is the mean (average) signalpower. The change of speech in time results in a wide dynamic range of average power. In addition to the predicteddynamics of average power, in the design of systems with adaptive techniques it is important to include otherparameters, among which is the Probability Density Function (PDF) of the average power. The goal of the researchpresented in this paper is the analysis of the probability distribution of the average power of speech signals, based onwhich the adaptability in the development of algorithms in digital processing would be improved, which wouldensure higher quality and less requirements in data transmission and storage. In addition to the theoreticalconsideration, the research was conducted on real speech signals of different speakers. In modern technical systems,where Internet technologies are prominent, processing, transmission and memorization of speech is executed frameby frame. Therefore, an analysis of the probability density of the average power for different frame lengths wascarried out in the experiment. In the experimental part, for each of the speech signals of the speech corpus, theProbability Density Function that best describes the average power values per frame was determined. Experimentalresearch results indicate that the function that best describes the average power is different for different speakers. Inaddition, when observing one speaker, the Probability Density Function is different for different frame lengths. Itcan be concluded that when it comes to adaptive techniques in the digital processing of the speech signal, it isimportant to consider the characteristics of the average power, among which is the Probability Density Function ofthe average power