Parameters setting of Frequency Converter PI regulation to ensure the vacuum of the milking process

This paper presents regulation of an asynchronous induction motor so as to create a stable vacuum milk pump using Variable Frequency Drive (VFD). Contribution includes providing information about the usage of the VFD, which regulates the activity of an asynchronous induction motor so that the vacuum pump milking machine creates stable vacuum. The paper describes the functional and time dependence of input values and output parameters of frequency converters at changing electric motor speed. For simulation and verification the milking process a mathematical model of the milking machine was created. The simulation was verified in Matlab/Simulink software. The constructed mathematical model showed symmetric regulation. Control model symmetry was verified at the laboratory of milking machine. The possibility to remove the control valve from milking equipment was proven using the measured data. It was found that constant vacuum values can be maintained. A constant vacuum can be maintained by changing vacuum pump speed. This control is of an accepted standard (ISO 5707: 2007). The power saving control values (on the milking equipment) of the VFD were positive throughout the measuring range. The performance of the milking vacuum pump is normally designed from the maximum air consumption of the milking machine at nominal vacuum (50 kPa), and a performance reserve is added to this. This means that the pump is operated between the ranges 7.53 and 15.06 dm(3) s(-1). By using a vacuum pump controlled by a VFD, power savings can be achieved from 32.50% to 54.02% compared to a control valve.Web of Science167art. no. e025342

Usage and support of geoinformation technologies in analysing the potential of compostable biomass in the Czech Republic

In the current society there is more and more effort to introduce, to make use of, and also to develop different information systems (IS). Nowadays it is already impossible to work without support of these systems for most institution of administration, private companies and single businessmen – if they want to be successful in their activities. So implementing and using of this IS become matter of fact. Waste management is one of sections, where these technologies are starting to influence as well. There is a development and implementation of the first IS in the level of single waste generators, regions and national administration as well. It happens to gradual data standardization presently because of unification and compatibility of single systems at all levels. The same situation is in section of Geographic information systems (GIS) as a one of parts of IS-subgroup. First nationwide projects, which can be also used in waste management, are starting to rise in GIS. Also this work is example of connection of GIS with one of waste management section – composting – and it shows possible practical usage on concrete examples

Evaluating the parameters of a mobile maize dryer in practice

The method of drying maize for grain has been recently employed on a large scale in the Czech Republic not only thanks to new maize hybrids but also thanks to the existence of new models of drying plants. One of the new post-harvest lines is a plant in Lipoltice (mobile dryer installed in 2010, storage base in 2012) where basic operational measurements were made of the energy intensiveness of drying and operating parameters of the maize dryer were evaluated. The process of maize drying had two stages, i.e. pre-drying from the initial average grain humidity of 28.55% to 19.6% in the first stage, and the additional drying from 16.7% to a final storage grain humidity of 13.7%. Mean volumes of natural gas consumed per 1 t% for drying in the first and second stage amounted to 1.275 m3 and 1.56 m3, respectively. The total mean consumption of electric energy per 1 t% was calculated to be 1.372 kWh for the given configuration of the post-harvest line

Analysis of production tests in processing the mixture of solid and liquid biologically degradable wastes by anaerobic fermentation

This study concerns the analysis of operating anaerobic fermentation systems of agricultural biogas station and implementing a suitable system enabling the use of a mixture of solid and liquid biowaste. The tests made use of liquid substrates commercially offered to biogas station operators. The study evaluates practical measurements at an agricultural biogas station in order to evaluate the biogas production from these substrates and the efficiency of transforming input material to usable energy. The use of such treated substrates for the anaerobic fermentation technology may have a substantial influence on the volume of dosed energy crops. The mixture of input substrates consisting of liquid cattle excrements, silage corn, solid and liquid waste from food processing, animal waste and glycerine water was experimentally validated. This mixture was compared with the operation using liquid cattle excrements and silage corn. It was concluded that the proposed composition of input raw materials makes it possible to increase the production of biogas and el. power. On the other hand, it was identified that the energy content of the input raw materials is not optimally transformed into usable energy. This is why the proposed mixture of input materials with biowaste is not recommended for use at the used proportion

Measurements of Flat-Plate Milk Coolers

Measuring in laboratory conditions was performed with the aim to collect a sufficient quantity of measured data for the qualified application of flat-plate coolers in measuring under real operating conditions. The cooling water tank was filled with tap water; the second tank was filled with water at a temperature equivalent to freshly milked milk. At the same time, pumps were activated that delivered the liquids into the flat-plate cooler where heat energy was exchanged between the two media. Two containers for receiving the run-out liquid were placed on the outputs from the cooler; here, temperature was measured with electronic thermometer and volume was measured with calibrated graduated cylinder. Flow rate was regulated both on the side of the cooling fluid and on the side of the cooled liquid by means of a throttle valve. The measurements of regulated flow-rates were repeated several times and the final values were calculated using arithmetic average. To calculate the temperature coefficient and the amount of brought-in and let-out heat, the volume measured in litres was converted to weight unit. The measured values show that the volume of exchanged heat per weight unit increases with the decreasing flow-rate. With the increasing flow-rate on the throttled side, the flow-rate increases on the side without the throttle valve. This phenomenon is caused by pressure increase during throttling and by the consequent increase of the diameter of channels in the cooler at the expense of the opposite channels of the non-throttled part of the circuit. If the pressure is reduced, there is a pressure decrease on the external walls of opposite channels and the flow-rate increases again. This feature could be utilised in practice: a pressure regulator on one side could regulate the flow-rate on the other side. The operating measurement was carried out on the basis of the results of laboratory measurements. The objective was to determine to what extent the use of flat-plate coolers under specific conditions results in cost reduction and improved milk cooling process. The measurement was performed in several cycles. The first measurement took place in the existing system without the use of the flat-plate cooler. The volume of drawn milk was monitored throughout the milking process along with its temperature, temperature in the tank and electricity consumption of the cooling system. At the second stage, the flat-plate cooler was introduced into the cooling process, which was followed by monitoring the milk and cooling water volume, their temperature, temperature in the tank and electricity consumption of the cooling system. The measured data indicate considerable power cost reduction if upstream flat-plate coolers are applied

Comparison of Conventional and Automatic Milking Systems at Extreme Conditions by Thermographic Method

The objective of this study is to evaluate the impacts of teat traumatization on Holstein cows caused by two different types of milking systems (CMS – conventional milking system and AMS – an automatic milking system). The experiments were performed in two locations: at Žabčice School Farm of Mendel University in Brno and at ZEMAX, a. s. in Šitbořice. For the evaluation of the degree of traumatization, thermographic images depicting surface temperatures of teats were used. This paper tested the hypothesis that, at extreme conditions, the teat traumatization of Holstein cows does not depend on used milking system. The hypothesis was disproved by the performed monitoring. From statistical point of view, it was observed that there were significant differences depending on which milking system was used

Analysis of the composition and formation of biogas produced during the processing of biological waste by anaerobic digestion technologies

This work compares the operating system of anaerobic fermentation of agricultural biogas plants with realization using biowaste. It deals with the operation system of anaerobic fermentation of agricultural biogas plants and implement an appropriate system to enable the use of biowaste. Based on the comparison of technological solutions and operational parameters of specific sites has been designed to allow the system biowaste were made a practical experiment to verify the assumption of increased biogas production. In experiments used substrates, which are industrially produced from the available bio-wastes, treated and then provide to operator of biogas plants. The work was carried out practical measurements to verify the production of biogas from different substrates. Utilize of nominal electric power using biowaste amounted up to 97.66%. Processing of such modified substrates in anaerobic digestion technology can greatly affect the amount of energy crops. Benefit of waste is governed primarily by such projects, where is the problem of ensuring sufficient energy crops. The proposed composition of raw materials also allows the implementation of the existing ope­ra­tion of anaerobic digestion. Operational data on real operations demonstrate the real possibility of further development of the area and secondly the use of biogas plants as well as in the preparation of suitably prepared substrates for the operators. The entire data set underwent a complete statistical analysis. Differences between variants were statistically significant

Measurement of Heat Losses on The Milking Machine Electric Motor at Various Regulations of Vacuum Using Methods of Thermal Imagery

To ensure the desirable vacuum in the milking machines, use is currently made predominantly of rotary vacuum pumps. These vacuum pumps are driven by a squirrel-cage induction motor. Until recently, the vacuum in the system to achieve the required value was controlled by a main control valve sucking in ambient air into the system. During the milking process itself and during other activities (flushing, sanitation), this control method consumed a large amount of electricity. The technical solution to electricity demand reduction was introduced with the emergence and development of frequency converters. The frequency converters control the operation of the asynchronous electric motor so that the actual delivery of the vacuum pumps equals the volume of air sucked into the vacuum pipe. The motor supply by the frequency converter brings about a host of adverse phenomena. This paper is dedicated to motor heating and heat losses on the surface of the electric motor at different regulations of vacuum in milking machines. The objective of the paper is to determine the immediate specific heat flows along the surface of the electric motor of the milking machine during milking using a control valve regulation and a control using the frequency converter, and compare the resulting value. The specific heat flows were determined by means of a non-traditional method of temperature field measurement using a system of thermal imagery. The calculated and measured data obtained from both these systems were statistically evaluated and compared. Use was made of a milking machine located in the cooperative Hospodářské obchodní družstvo (HOD) Jabloňov