Rotor Coils Research Articles

Electro-thermal dynamics in superconducting generators: An In-Depth investigation of AC losses and cooling techniques for a 10 MW rotor coil system

In the pursuit of optimizing superconducting generator systems, a comprehensive understanding of their electro-thermal behaviors is crucial. This study builds upon previous research on an 8-pole, 10 MW superconducting generator by Inanir et al. (2022, Journal of Superconductivity and Novel Magnetism, 35(11), 3189) and focuses on an in-depth electro-thermal analysis of the rotor coil system. The emphasis is on assessing the AC losses experienced during transitory current changes. By simultaneously solving Ampere's equation and the heat conduction equation under specific boundary conditions, the research provides a detailed insight into the interaction between electrical and thermal dynamics within the rotor coils. The paper highlights the importance of temperature dynamics in various cooling and current conditions. The results demonstrate that achieving an optimal balance in cooling, particularly with the use of liquid nitrogen, is critical for efficient operation. This study not only advances the understanding of superconducting generators but also highlights potential strategies for improving their reliability and efficiency.

Airplane motors employing superconducting DC field windings and conventional conductor AC windings

Many organizations are developing compact lightweight highly efficient rotating machines for airplane applications. These machines include permanent magnets for excitation and an iron-core with and without superconducting windings. Air-core (no magnetic iron) machines have the potential to be the most lightweight and efficient. Such machines can use superconductors for both DC excitation field coils and AC armature coils, which need conductors under development, like MgB2 and Bi2212. If liquid-hydrogen (LH2) is available on a plane and can be used as a coolant, it becomes feasible to develop machines with AC armature coils made from conventional conductors like copper, aluminium, and high-conductivity aluminium.This paper describes conceptual designs for a 3 MW, 4,500 RPM motor employing REBCO CORC conductor for the DC field coils and conventional conductor Litz cable for the AC armature coils cooled by LH2 available on the plane. Both rotor and stator coils are contained in separate cryostats. The DC excitation coils on the rotor are operated at 40 K to work successfully with a brushless flux pump exciter. Likewise, stator AC coils are cooled with available LH2 to take advantage of the lower resistivity of conventional conductors at cryogenic temperatures. Motor size, mass and losses are compared for stator windings employing copper, aluminium, and high-conductivity aluminium (Hyper-Al). Compared with copper and aluminium machines, the machine employing Hyper-Al has smaller size, mass and total losses.

Application and Comparison of a Modified Protection Scheme Utilizing a Proportional–Integral Controller with a Conventional Design to Enhance Doubly Fed Induction Generator Wind Farm Operations during a Balanced Voltage Dip

The doubly fed induction generator (DFIG) is vulnerable to grid faults due to its direct stator connection, causing issues like excess stator current during voltage dips. Consequently, sensitive inverters suffer from increased currents, and the DC-link capacitor undergoes overcharging. This document examines two protection strategies employing a proportional–integral (PI) controller to manage the transient rotor current and mitigate DC-link overcharging, thereby optimizing DFIG behavior during network faults. One option combines a classic crowbar circuit with a DC-chopper, while the other is a modified protection scheme (MPS) that includes an impedance with passive elements and a crowbar. The impedance forms a resistance Rp parallel with an inductance Lp. Both configurations, situated between the rotor coils and the rotor-side converter (RSC), augment the capacity for low-voltage ride-through (LVRT). MATLAB/SIMULINK simulations of the two schemes demonstrate successful rotor current reduction at 2.9 kA and 3.4 kA, and DC-link tension reduction below and at 1.4 KV. In addition, the conventional crowbar and MPS configurations efficiently restrict the RSC current to levels below 0.21 kA and 2.94 kA, while absorbing up to 2.52 kA and 1.52 kA, respectively. The key difference lies in the fact that fine-tuning the parameters in the MPS design prevents rotor disconnection when faced with a balanced fault. This enhancement enhances machine performance and enables full stator power control via the RSC.

Superconducting Synchronous Motor Development for Airplane Applications - Mechanical and Electrical Design of a Prototype 100 kW Motor

A 100 kW, 4500 RPM synchronous superconducting motor is being built at the Paihau-Robinson Research Institute, Victoria University of Wellington, New Zealand. The motor has superconducting excitation field coils on the rotor and a conventional stator winding. To minimize mass the motor is an air-core type, meaning no ferromagnetic materials are employed inside the motor. Some of the salient features of this motor include: 1) field winding coils employing REBCO CORC conductor; 2) field coils powered with a contactless superconducting dynamo exciter; 3) an EM shield on the rotor for protecting the field coils from high frequency magnetic fields due to stator harmonics and the switching of the drive electronics; 4) a unique single-layer winding design for the stator winding, where the stator coils are made with copper Litz wire and are liquid-cooled. This paper describes the electrical design and 3D simulation of the motor including the superconducting dynamo, and highlights stator and rotor coil developments that will be validated in the prototype. Sensitivity to critical design parameters has been assessed in simulation and initial sub-system prototypes manufactured for testing. Preliminary design is projecting this motor diameter and axial length as 360 mm and 550 mm respectively, with an efficiency of 96.4 % at the rated load. These numbers may be comparable with permanent magnet motors of similar rating, but this motor is being built to serve as a test-bed for evaluating different technologies for rotor and stator components. The ultimate goal for this program is a 3.0 MW machine with superconducting armature and field windings. In comparison with the permanent magnet motor in 2.5 - 3.0 MW range, the superconducting motors are expected to be 4 to 5 times smaller in size and mass with efficiency exceeding 99 %.

Enhancement of LVRT Ability of DFIG Wind Turbine by an Improved Protection Scheme with a Modified Advanced Nonlinear Control Loop

One of the problems with the doubly-fed induction generator (DFIG) is its high vulnerability to network perturbations, notably voltage dips, because of its stator windings being coupled directly to the network. As the DFIG’s stator and rotor are electromagnetically mated, the stator current peak occurs during a voltage dip causing an inrush current to the critical converter back-to-back and an overload of the DC-link capacitor. For this purpose, a series of researchers have achieved a linear and non-linear controller with a crowbar-based protection scheme. With this type of protection, the Rotor Side Converter (RSC) is disconnected momentarily, and consequently, its control of both the active and reactive output power of the stator is totally lost, leading to incorrect power quality at the point of common coupling (PCC). In this document, a robust nonlinear controller by Advanced Backstepping with Integral Action Control (ABIAC) is initially employed to monitor the rotor and the network side converters under normal network operations. In the presence of a network fault, an improved protection scheme (IPS) is tacked on to the robust nonlinear control to help enforce the behavior of the DFIG system to be able to overcome the fault. The IPS, which is formed by a crowbar and an RL series circuit, is typically located in the space between the rotor coils and the RSC converter. Compared to a standard crowbar, the developed scheme is successful to limit the rotor transient current and DC-link voltage, also an RSC disengagement to rotor windings can be prevented during the fault. Furthermore, the controllers of both the RSC and the Network Side Converter (NSC) are modified to boost the supply voltage at the PCC. A comparative study is also performed between the IPS without and with modification of the reactive power control loops. The simulation results mean that with the modified controllers during the fault, the amount of reactive power sustainment with ABIAC at the PCC is optimized to 17.5 MVAr instead of 15 MVAr with proportional-integral control (PIC). Therefore, the voltage at the PCC is fort increased in order to comply with the voltage requirements of the farm and absolutely to maintain the connection to the network in case of voltage dip.

Thermographic fault diagnosis of electrical faults of commutator and induction motors

In this paper, the author proposes a fault diagnosis technique for the analysis of thermal images of commutator motors (CMs) and single-phase induction motors (SIMs). The aim of scientific research is to confirm the effectiveness of the proposed technique for the analysis of thermal images of electric motors. Original feature extraction methods: DAMOM (Differences of Arithmetic Mean with Otsu’s Method), DAM20HP (Differences of Arithmetic Mean with 20 Highest Peaks), DAMMH (Differences of Arithmetic Mean with Mean of the histogram), IB (Ignore Binarization). The Nearest Neighbor classifier and Long short-term memory (LSTM) classified feature vectors. The thermal imaging camera was moved 0–1 [m/s2] vertically, during the measurements. Thermal imaging measurements with shivering and analysis are a novelty for fault diagnosis methods. The following conditions of motors were analyzed: healthy commutator motor (HCM), broken rotor coil of the commutator motor (BRCoCM), shorted stator coils of the commutator motor (SSCoCM), healthy single-phase induction motor (HSIM), single-phase induction motor with shorted coils of auxiliary winding (SIMwSCoAW), single-phase induction motor with shorted coils of auxiliary winding, and main winding (SIMwSCoAWaMW). The proposed analysis was successful. The value of AMECM (Arithmetic mean of the efficiency of recognition) was equal to 100% for the analyzed states of the CM. The value of AMESIM was in the range of 95.33%–100% for the analyzed states of the SIM. The original perspective of the presented study is to develop techniques of thermal imaging diagnostics. Readers can learn about the subject of thermographic diagnostics of electrical motors. Readers also gain knowledge about the processing of thermal images. A literature review on the diagnostics of electric motors was also presented.

Conceptual design, AC loss calculation, and optimization of an airborne fully high temperature superconducting generator

With the trend of multi-electrification and hybrid-electrification of aircraft, the airborne high temperature superconducting (HTS) generator is considered as the key technology of the new generation of aviation power generation system and has received wide attention. The high critical current and low loss of superconductors can significantly improve the output power, power density, efficiency and other performance of generators. In this work, conceptual design of a fully HTS generator for aircraft is carried out to address key issues in terms of AC loss distribution, which serves as the ground of cryogenic design in the future. A 10 MW fully superconducting generator is designed to be used in a large passenger aircraft (with more than 150 seats and a maximum takeoff weight of about 100 tons). Based on the finite element method (FEM) with the so-called T-A formulation, the electromagnetic characteristics of the generator are analyzed, and AC losses of the stator and rotor are calculated. To calculate the rotor loss in realistic dynamic-field environment, a technique named “rotation-domain exchange” is developed and implemented. By using such technique, accurate calculation of AC loss of the rotor in realistic dynamic electromagnetic environment is achieved with no need of simplified boundary condition as previously reported work. Based on the model, the stator coil structure is optimized to reduce the AC loss and the rotor coil structure is optimized to reduce the HTS tape usage. Results show that the optimized stator AC loss is 15.645 kW, and the rotor AC loss is 6.268 kW, indicating that the rotor AC loss of a fully superconducting generator with narrow air gap and large number of coil turns is not neglectable as previous work assumed. Thus, precise calculation and dedicated optimization of the rotor loss is critical since cooling of the rotor is much more challenging than the stator as the former remains in motion.

Finite element method applied to magnetic flux analysis in large synchronous machines with short circuit faults in the rotor

This paper presents a study of magnetic flux density in a large synchronous large size machine when it is working as a generator. Finite elements software has been used to obtain the same physical and electrical characteristics of the real machine. From the results conveyed from the simulations, it is possible to find the optimal points where the magnetic flux sensors will be placed and to determine short-circuit faults in the rotor coils. The work results are also a reference to evaluate and compare the magnitudes taken by the sensors without creating short-circuits in the actual machine coil. Besides that, the proposed model based on finite elements can be used to make simulation tests of new kinds of sensors.

Computational Design Analysis of a Hydrokinetic Horizontal Parallel Stream Direct Drive Counter-Rotating Darrieus Turbine System: A Phase One Design Analysis Study

This paper introduces a phase one computational design analysis study of a hydrokinetic horizontal parallel stream direct-drive (no gear box) counter-rotating Darrieus turbine system. This system consists of two Darrieus rotors that are arranged in parallel and horizontal to the water stream and operate in counter-rotation due to the incoming flow. One of the rotors directly drives an armature coil rotor and the other one a permanent magnet generator. A two-dimensional (2-D) and three-dimensional (3-D) computational fluid dynamic (CFD) simulation study was conducted to assess the hydrokinetic performance of the design. From a high computational cost and time perspective, the simulation setup was reduced from a 3-D to a 2-D analysis. Although useful information was obtained from the 3-D simulations, the output performance could be assessed with the 2-D simulations without compromising the integrity of the turbine output results. A scaled experimental design prototype was developed for static (non-movement of the rotors with dynamic fluid flow) particle image velocimetry (PIV) studies. The PIV studies were used as a benchmark for validating and verifying the CFD simulations. This paper outlines the prototype development, PIV experimental setup and results, computational simulation setup and results, as well as recommendations for future work that could potentially improve overall performance of the proposed design.

Hydrogen production from Al–Cu alloy using electric vehicle's waste DC motor coils

Electric vehicles are a viable alternative for internal combustion engine cars to overcome transportation problems due to high fossil fuel consumption and greenhouse gas emissions. Due to their direct current motor and battery technologies' technological development, they have become an efficient transportation option in the last decades. However, the rapid spread of electric vehicles will bring huge dump problems for the environment. Thus, policies related to the recycling of their components must be carried out. In this study, an Al–Cu alloy is developed from the waste direct current motor's Cu rotor coils and pure Al for hydrolysis reactions. Then, 2 wt%, 4 wt% and 6 wt% Cu are added to pure Al to observe different Cu addition to Al–Cu alloy's hydrogen production performance to varying temperatures like 40, 60, and 80 °C. In 40 °C, 6 wt% Cu added Al alloy has around two-fold higher hydrogen production than pure Al. Moreover, the hydrolysis reaction's activation energy is decreased from 81.56 to 35.5 kJ mol −1 in 6 wt% Cu added Al alloy. • Al–Cu alloy is developed from waste DC motor's Cu rotor coils and pure Al. • Activation energy is decreased from 81.56 to 35.5 kJ mol −1 in AlCu6 alloy. • In AlCu6 alloy, 0.17 ml s − 1 hydrogen generation rate is obtained at 40 °C. • Corr rate of the pure Al is changed from 28.78 to 86.56 ml g −1 min −1 by 6 wt% Cu addition.

Design generator of magnetic power (Based on gap rotor-stator motor magnet)

The paper discusses magnetic power generators; if a conductor moves across the magnetic field, a voltage difference will occur at the ends of the conductors. The voltage rises as it approaches the area and vice versa, so electricity arises in cycles: positive - zero - negative - zero. In this study utilizing the rotation of a magnetic motor caused by the unbalance repulsive force between magnets. The design of the tool starts with designing a generator model that will be made. The design of generators is based on calculations obtained through the reference of generator design. The generator design uses magnets instead of anchor coils on the rotor (source of magnetic flux) and copper wire coils as anchor coils on the stator. This design considers rotor and stator parameters, including the distance between magnets, rotor diameter, rotor plate thickness, area of a magnetic area, number of stator coils, number of stator windings, and stator coil dimensions, and calculate generator output power. Tool testing is done to obtain data from tools that have been made. In testing the comparison of the results obtained from the study of the target to be achieved, if the results have not yet reached the target, then improvements are made to the results obtained as expected. Tests were carried out with no load and burden. The results showed that the rotor speed in the generator design could be achieved by determining the number of rotor poles, the generator voltage is influenced by the flux density produced by permanent magnets and the number of stator windings.

Minimization of the Electromagnetic Torque Ripple of a Synchronous Reluctance Generator Using External Rotor Excitation

This paper presents an approach to minimize the electromagnetic torque ripple of a synchronous reluctance generator (SynRG) with a magnetic field created by externally excited rotor coils. The synchronous reluctance machine is widely used in low and medium power systems such as wind power generation and new electric vehicle technologies. This paper proposes a rotor topology with flux barriers and direct current excited coils that reduce the torque ripple and replace the permanent magnets used in other reluctance rotor topologies. First, the initial rotor design, without excitation coils, is optimized to obtain a new rotor structure that reduces the electromagnetic torque ripple. In this work, the optimization of the rotor geometry was achieved by using genetic algorithms and the finite element method to optimize and parameterize the main components of the machine. In the optimized rotor model, an external electronic converter is included to feed the coils positioned between the magnetic flux barriers and the segments formed by the ferromagnetic material of the rotor. Finally, the electrical and magnetic machine variables obtained from implementing the coils into the optimized rotor are compared to the initial rotor structure operating under nominal load conditions to demonstrate the advantage of this topology in minimizing the electromagnetic torque ripple.

Superconductor fault current limiter effect on the performance of doubly-fed induction generators

<span>Between different wind turbine-generator configurations, one of the most accepted and highly regarded structures in the industry is the wind turbine with doubly-fed induction generator. The DFIG wind turbines are very sensitive to grid disturbances especially to voltage drop during grid faults due to relatively low power of the power converters. Fault in a power system causes voltage drop, current increase in stator and rotor coils, and over voltage in the DC shin. Several control methods have been proposed so far. A model based on power electronic instruments and superconductor theory, superconductor fault current limiter (SCFCL), has been proposed in this paper to improve domain and the attenuation time of the parameters under control such as voltage, current, and speed and voltage of the DC link against various types of faults (single-phase, two-phase, and three-phase). In addition to this, in order to compare the results with convectional models (crowbar) and study the innovation of the proposed model, a simulation of the system under two-phase fault and use of crowbar method to control the fault has been conducted using MATLAB-SIMULINK and also, the performance of the proposed method has been assessed. </span>

General Design of a 300-Kvar HTS Synchronous Condenser Prototype

China Southern Power Grid Corporation has started a project to study the feasibility of large-scale high-temperature superconducting (HTS) dynamic synchronous condensers (DSC) in Ultra High Voltage Direct Current (UHVDC) transmission grid. To investigate some key technologies, a small-scale prototype of HTS DSC of 300 kvar/2 poles/3000 RPM is under development. The electromagnetic design, especially the critical current of REBCO rotor coils was discussed. Besides, the configuration and properties of the air-core stator, the damper and the rotor were also described. Water-cooled windings in the air-core stator have a rated current density of 9.55 A/mm 2 . Helium cooling pipes were embedded within REBCO rotor coils, and HTS windings will be cooled down to <; 30 K (<; 25 K for better) through conduction cooling. Two REBCO coil assemblies were manufactured and successfully tested in liquid nitrogen for several thermal cycles, which validated the manufacture techniques.

Unified Analysis of Induction Machine and Synchronous Machine Based on the General Airgap Field Modulation Theory

This paper investigates the natures of induction machine (IM) and synchronous machine (SM) from a new point of view based on the general airgap field modulation theory. The equivalent airgap model containing three critical elements is proposed to expound their modulation principles and common features in a unified way, thus the electromagnetic performance analysis, i.e., back-electromotive force (EMF) and torque, of IM and SM can be put together from the perspective of airgap field modulation principle while the only difference exists in the modulators. The modulators are optimized by considering the nonlinearities like rotor coils resistance and leakage inductance of IM and the actual magnetomotive force (MMF) distribution of SM. Theoretical expressions of airgap flux density distribution, flux linkage and EMF, general average torque, torque density comparison, and inductance characteristics are developed to reveal the relation between the performances and initial key topological parameters systematically and verify the model feasibility entirely. The iron saturation is treated as a constant discount on the airgap MMF to provide general mechanism comprehension and reasonable parameters calculation. All the theoretical predictions are verified by two-dimensional (2-D) finite element analysis together with experiment achieving good agreement.

Quasi-Static Torque Profile Expressions for Magnetic Resonance-Based Remote Actuation

Resonant wireless power transfer has been employed to transfer electrical power from a transmitter to a receiver coil over an air gap and to remotely charge consumer devices. In this paper, the receiver coil is replaced by a stator–rotor topology, enabling magnetic resonance based motoring over substantial air gaps. The principles of resonant wireless power transfer are used to induce currents in a strongly coupled magnetic resonance system. This results in its turn-in torque, which is applied on the rotor body, allowing for remote actuation. We propose a voltage or current controlled magnetic resonance motoring topology, for which we derive expressions for the generated torque depending on the rotor angle. Furthermore, torque profile expressions are derived for motoring systems with multiple stator and/or rotor coils. Finally, an experimental setup is built to validate the obtained torque expressions. Using the validated expressions, we present a sensitivity analysis of the key system parameters with respect to the torque profile. The presented torque profile expressions enable further topology exploration and optimization of magnetic resonance based motoring systems.

Torque coefficient analysis of a novel direct-drive parallel-stream counter-rotating darrieus turbine system

This research project introduces a novel hydrokinetic turbine system called a direct-drive parallel-stream counter-rotating darrieus turbine (DD-PS-CRDT). Two darrieus rotors are arranged horizontally across the water stream, one directly driving an armature coil rotor and the other a permanent magnet rotor of a generator. The proposed system improves on other counter-rotating turbine systems because each rotor utilizes a separate stream, direct-drive eliminates friction losses in the gearbox and the generator's rotational speed is doubled. This study emulated the DD-PS-CRDT by writing a simulation program using Visual Basic and Matlab codes. Turbine system configurations had different numbers of blades and lag angles between the rotors. Torque coefficient (CT) profiles and ripples were investigated in the interest of torque output smoothing. The system with the lowest ripple was found and a table of prescribed lag angles presented. It is noted that both the magnitude of the minimum ripple and the corresponding lag angle change with rotational speed (ni). Moreover, the CT output profile varies greatly with ni and a few curves contain irregular spikes. However, the evidence suggests that it is possible to maintain smooth curves, especially at the rated speed (ns).

Influence of incident angle of hydrogen in the ventilation ducts on multi-physical fields of 1100 MW turbine-generator rotor

During the operation of a large-scale turbine-generator, hydrogen enters the ventilation ducts of the rotor with turbulent state, so that the inlet direction of hydrogen is difficult to solve under the influence of rotor rotation. The cooling effect of the rotor coil can be effected by the mainstream of hydrogen entering the ventilation ducts. With regard to this, it takes an 1100 MW turbine-generator with axial ventilation system, as a test generator, global fluid network equation is carried out to calculate the pressure field and velocity field of hydrogen in the rotor ventilation ducts. Based on the calculations, the fluid and heat transfer nonlinear equation for the rotor is established and calculated via finite volume method (FVM). First, the hydrogen flow law in the complex ventilation duct is investigated and the pressure losses of hydrogen in the corners from the rotor radial inlet area to the axial flow area and then into the radial outlet area are analyzed. Second, the rotor temperature fields are highlighted and investigated in the condition of incident angle α = 0°, 15°, 30°, 45°. The incident angle α = 0° indicates vertical state between hydrogen flow direction and the rotor vent inlet. Simultaneously, the calculations of the average temperature in the rotor coils are compared with the experimental results to verify the accuracy of the calculation method. Additionally, the temperature distribution of rotor varying with the circumferential direction is investigated, which can provide theoretical basis for the larger scale turbine-generator.

Design considerations for electric motors using stacks of high temperature superconducting tape as permanent magnets

High temperature superconducting (HTS) tape can be cut and stacked to form composite bulks capable of generating fields as high as 17.7 T, the highest of any trapped field magnet. This makes them the most powerful permanent magnets accounting for the need to maintain a cryogenic temperature. This cryogenic penalty is increasingly being justified due to the significantly higher power densities (>10kW/Kg) fully superconducting motors can enable by using magnetized stacks of tape on the rotor and HTS coils on the stator. Design considerations for a motor using magnetized stacks for aerospace applications will be presented including FEM modelling in COMSOL and experimental prototype results for candidate designs. The rotor AC loss due to heating by ripple fields will be discussed based on these results and its interdependence with stator AC loss in a fully superconducting motor which has not always been appreciated in previous partially superconducting motor designs.

АНАЛІЗ ПРИЧИН РУЙНУВАННЯ БАНДАЖНОГО КІЛЬЦЯ ТУРБОГЕНЕРАТОРА

Description of the destruction (emergency) of a retaining ring of a pre-series Turbogenerator of medium power is submitted in the scientific work. The following destructions were detected: rupture of the back part of the rotor retaining ring as per the generatrix, complete destruction of the external ring of the fan, blades, diffuser, tearing-off of the rotor coils, cutting of the rotor winding and its fastening parts, severe damage of the whole overhang part of the stator winding, complete destruction of the top row of the stator winding bars in the overhang part, rupture of the elementary conductors. The causes of destruction (emergency) are submitted: availability of cracks on the external surface of the rotor ring of Turbogenerator, nonconformity to the specifications on the plastic properties of the retaining rings metal, admission of the defects at manufacturing of the Turbogenerator rotor retaining ring at the manufacturer-plant (rough treatment of the retaining ring surface, availability of nicks and scratches, eight-fold heating of the retaining ring, fire in the generator). The design peculiarities of the rotor retaining ring of Turbogenerators. The causality analysis of the retaining ring damage was carried out. It is shown that the cause of the emergency can be a chain of events not related to each other and individually each leading to a failure or emergency. It is found that the events, the probability of which lies on the edges of the power-series distribution, the so-called "heavy tail" distributions shall become the most probable if they can cause maximum loss due to damage. One approach is considered in an attempt to answer the question: whether there are objective regularities in describing the consequences of major emergencies and catastrophes in the technosphere and in nature. Since the probability of a defect in the part shall be inherent for all stages of the service life cycle of the design (design working out and studying, technological preparation, manufacturing of the part, testing for compliance with the technical parameters, assembly, testing of the general design), then for the most unfavorable event with "heavy tails" the decisive factor shall be the human factor, to predict the change and behavior of which is almost impossible. The sequence of execution of technological operations for the elimination of rejection is established.