1,721,055 research outputs found
A review on active magnetic bearing system limitations, risks of failure and control technologies
Get PDFThis paper provides a review on active magnetic bearing (AMB) system limitations, risks of failure and control technologies. Details regarding the operation of an AMB system and background on bearings and sensors are provided. The following benefits for AMBs was identified and are discussed: 1) high reliability, 2) clean environment, 3) high speed applications, 4) position and vibration control, 5) equipment design, development and testing, 6) machine diagnostics, 7) elimination of oil supply, 8) low power consumption and long life, 9) low weight and 10) capability to operate under extreme conditions. The paper further discussed the limitations of AMBs under the following headings: 1) larger bearings, 2) higher complexity and cost, 3) requires electrical power and 4) windage losses. System faults can be broadly classified as either internal or external to the magnetic bearing control system. This classification then relates to the way in which the faults can be dealt with following occurrence. The measures for reducing risks of failure include the following: 1) quality control and standards, 2) systematic check of the design, 3) software development system, and 4) redundancy. Possible future AMB control technologies are likely to be driven by 1) higher operating speeds, 2) lower power loss, 3) greater use of the available clearance, 4) generalised actuation, sensing and control and 5) control of the unbalance response, which are all discussed in this paper. The paper ends with a conclusion on the review of AMB system limitations, risks of failure and control technologie
Environmental impact of an industrial compressed air system with a solar powered compressor in South Africa
Get PDFAlmost 14% of the electricity generated by the national energy supplier (Eskom)
in South Africa is sold directly to the mining sector and almost 20% is utilized
directly by the compressed air systems of the mining sector. The industrial
compressed air systems in South Africa therefore have a substantial impact on the
environment in terms of emissions output. In this paper a solar powered
compressor is installed parallel to an existing industrial compressed air system.
The environmental (emissions) impact and energy consumption of the industrial
compressed air system with the solar powered compressor is calculated and the
results are provided. It is shown from the results that the solar powered air
compressor improved the overall system efficiency and lowered the carbon
footprint of the industrial compressed air system. The impact of the energy
improvement on the amount of trees required to offset the calculated amount of
CO2 is also provide
Efficiency analysis of an induction motor with field oriented control at a hot rolling mill
Get PDFIn this paper, the efficiency analysis of an induction motor with field-oriented control (FOC) at a hot rolling mill in South Africa is presented. It is shown that the energy consumption of an induction motor at a hot rolling mill can be improved with the introduction of FOC with a variable input reference compared to direct torque and flux control (DTC) with a fixed input reference. An overview on the control process of the induction motor with FOC and the schematics of the field-oriented controller are presented. Results for the following two scenarios are presented: 1) the induction motor is controlled at a constant speed with a variable thickness slab by means of DTC and 2) the induction motor is controlled according to the thickness of the slab by means of FOC. Overall results obtained showed an average improvement of 3.67% in the energy consumption of the experimental test setup system from scenario 1 to scenario 2. The simulation and experimental results that illustrate the performances of the proposed scenarios are also presente
Fault detection techniques on active magnetic bearing systems and electrical machines: a review
Get PDFThis paper provides a review on fault detection techniques on active magnetic bearing systems and electrical machines. The following
non-linear processing fault detection techniques are discussed in this paper: 1) Time domain analysis, 2) Frequency domain analysis, 3)
Time-frequency analysis, and 4) Feature analysis. Time domain analysis is discussed and broken up into data collection, time domain
features and Weibull distribution. Frequency domain analysis is discussed and broken up into Cepstrum analysis, enveloped spectrum
analysis, equi-sampled discrete Fourier transform, high frequency resonance technique, shock pulse analysis and spike energy analysis.
Time-frequency analysis is discussed and broken up into short-time Fourier and bilinear transform, which includes Wigner-Ville distribution. Feature analysis is discussed and broken up into artificial neural networks, feature selection and extraction, feature set reduction,
fuzzy logic and pattern recognition. This paper focuses only on nonlinear fault detection techniques and ends with a conclusion on the
discussed fault detection techniques for active magnetic bearing systems and electrical machine
Condition monitoring analysis methods for electrical machines: a review
Get PDFThis paper provides a review on condition monitoring analysis methods for electrical machines. An overview of condition monitoring is
provided where online as well as offline monitoring is discussed. A section on vibration monitoring is included, since vibration monitoring is one of the most important online monitoring techniques. As part of vibration monitoring, background vibration, the effect of machine speed and load and variation of a signal at constant operating conditions are discussed. The paper further discussed time and process domain averaging, temperature effects, spurious low frequency ‘ski-slope’ effect and evaluation standards related to vibration monitoring. Various analysis methods exist for the condition monitoring of machines. These analysis methods are divided and discussed in
this paper as deterministic and non-deterministic (or statistical analysis approach) methods. The paper ends with sections on condition
monitoring measurements and noise filtering during condition monitorin
Analysis of a 405 km transmission line with series compensation
Get PDFThis paper presents an investigative case study and energy efficiency analysis of the 405 km, 420 kV transmission line between Insukamini
substation in Bulawayo in Zimbabwe and the Matimba thermal power station in South Africa. Three scenarios were evaluated: 1) where a
line to ground fault occurred on the secondary bus, 2) where an impedance fault occurred on the two transmission lines and 3) where the
combination of the above two faults occurred. An analysis was made on the energy efficiency of the load with respect to the three scenarios
by means of a simulation modelThis paper was presented at the 2011
Industrial and Commercial Use of Energy
Conference, Cape Town, August 2011,
and is reprinted with permissio
Energy management by means of SMD model analysis for AMB systems with eccentricity
Get PDFThis paper provides the spring-mass-damper (SMD)
model analysis of a radial active magnetic bearing (AMB)
system that displays eccentricity. Energy management of AMB
systems can be done by means of a detailed SMD model analysis.
It is specifically important to use SMD model analysis when the
AMB system displays eccentricity. A SMD model analysis as
well as the free-body diagram analysis is presented for the
following scenarios: 1) rotational load unbalance, 2) foundation
looseness, 3) rotating overhung rotor, 4) static eccentricity and
5) dynamic eccentricit
Energy management by means of PLC for a solar powered ultra-capacitor streetlight system
Get PDFThis paper presents the design of an energy
management programmable logic controller (PLC) control
program for a solar powered ultra-capacitor and battery
powered streetlight system. A PLC is used to control the flow of
energy between an ultra-capacitor bank and a deep-cycle
battery bank for a solar powered streetlight system. The
purposes are to increase the efficiency of the complete solar
powered system and to prolong the lifetime of the battery bank,
since deep-cycle batteries normally used in solar electrical
systems, generally have low efficiencies, have a limited amount
of charging and discharging cycles, have long charging times
and are temperature sensitive. The designed operational
diagram as well as a functional block diagram of PLC control
program is presented. The results of five different scenarios
pertaining to the functionality and use of the energy between the
ultra-capacitor bank and deep-cycle battery bank are presented
in this pape
Impact of frequency switching on the efficiency of a fully suspended active magnetic bearing system
Get PDFDue to the rising energy (and electricity) cost it is essential that an active magnetic bearing (AMB) system is operated as efficiently as possible. Frequency switching caused by an external source can cause an AMB system to operate at a higher than expected energy level and lower than expected efficiency. The purpose of this paper is therefore to investigate the impact of frequency switching (caused by an external source) on the efficiency of a fully suspended AMB system. The shaft of the fully suspended AMB system for this project is mechanically connected and driven by an induction motor and the vertical and horizontal displacements of the driven unit are controlled by means of PID controllers. The model of the fully suspended AMB system with the external fault and the process diagram used for frequency extraction during the fault condition is presented. It is shown that the efficiency of the fully suspended AMB system can be improved by optimizing the controller performance during the external fault condition
Renewable energy thermoelectric module air conditioning system-design factors: a review
Get PDFThe conventional air conditioner is fast becoming a noticeable
energy user that negatively affects the supplier’s ability to
supply energy during peak periods when the country’s energy
need rises. The Clean Development Mechanism (CDM)
stipulates that a country committed under the Kyoto Protocol,
has to implement emissions-reduction programs in developing
countries to help reduce the CO2 emissions around the world. It
is therefore important to invest in renewable energy projects
and perform research on air conditioning systems, in order to
lower the energy strain on the electricity grid and contribute
towards CDM. This paper therefore provides a review on the
factors that need to be taken into account and the different
technologies that can be used in the design of a renewable
energy thermoelectric module (TEM) air conditioning system
for South African conditions. The different technologies in the
design are compared to each other by means of a unique tradeoff study, in order to design the optimal efficient and cost
effective renewable energy TEM air conditioning syste
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