Energy economy in electric drive is part of general process of the effective use of electric power and is determined by three processes:
• by energy consumption;
• by energy use of consumable energy;
• by the energy control of process of energy consumption.Energy consumption is the process of forming of constituents power on the entrance of transformer during work of electric drive. This process is characterized by dependences of active, reactive and powers of distortion from speed and moment of engine, by the indexes of quality of electric power and their influence on descriptions of electromechanical transformers.
Energy used is the use of power of consumed from a circuit. This index characterizes the high-quality side of process of energy consumption. It shows as far as the use of consumable electric power is effective, which part from its belong to the losses, and which – to useful power going to the shaft of working machine. How the losses, which determine the operating condition of electric motor, its temperature and reliability, are distributed and allows to expose the mechanisms of senility of electrical equipment.
Energy control is the process of forming of the modes of energy consumption by the technical devices and systems which influence on the control circuit by the electric drive and converter installation, feeding these controls. The control by the redistribution of losses in electric engines, optimization of losses, minimization of heating of active parts of electric machine, decline of levels of consumable reactive power and generation of current belong to energy control.
Such energy approach, which is based on general processes of energy consumption, energy used and energy control, binds in a single electromechanics complex the elements which examined without intercommunication before: power network, user (electric drive) and technological setting. Each of components have their regulation positions in area of management by energy consumption, redistribution of losses and so on.
The first way behaves to simplest out of control most mass electric drive and consists of perfection of procedure of choice of engine for the concrete technological setting with the purpose of observance of the nominal thermal mode of engine during exploitation.
Target setting is obvious - the engine of the understated power fast falls out, and the engine of the overpriced power transforms energy uneffective, in other words, with the high specific losses in an engine (low KPD) and in tricking lines into (low cosj). Task solution not always is elementary, errors, and as there are simplest electric drive of million, so a great damage is possible. In the cases when loading is unchanging, errors are caused only by low qualification of developers (an engine was chosen on the diameter of shaft). When load changes, the choice appears considerably more difficult, that is yet intensify by insufficiency of source information, passport and catalogue data.
The second way of increase of economy of mass constitutive electric drive is transition on energy economy engines and engines of the improved construction which specially intended for work with managed electric drive. Energy economy engines have higher basic values of KPD and cosj due to the increase of mass of active materials (iron and copper).
Energy economy engines are used, for example, in the USA, and is given an effect at the dead load. Efficiency of the use of energy economy engines will be the higher, than more load of engine and than the mode of operations of its to the dead load is nearer. Expedience of used of energy economy engines must be estimated taking into account additional expenses, as to KPD and are achieved the small (to 5%) increase of nominal due to the increase of mass of iron on 30-35%, coppers on 20-25%, aluminium on 10-15%, i. e. rises in the prices of engine on 30-40%.
The third way is the removal of intermediate transmissions. The heart of problem consists of that electric energy is accessible on the fixed frequency (50 Hertzs), and mechanical energy is required in the wide spectrum of frequencies (speeds). The methods which are developed a many years ago for the decision of this problem use the expensive systems generator-engine or mechanical regulators.
Generalized circuit of electric drive consist of: transformer or mechanical regulator (box of speeds, muff of sliding), muff, reducing gear and working organ being part of working machine.
The approximate meaning of KPD of elements of drive are made:
• transformer - (less meanings for small speeds of rotation, large - for more high speeds);
• engine -(less meanings for microscopic machine, large - for the machines of the promoted power);
• mechanical regulator - ;
• muff -;
• reducer;
• working arrangements - (for the drive drum of band conveyer).A fourth way consists in the increase of efficiency of work of electric drive, i.e. in the choice of rational operation mode and exploitation of electric drive. Here get in:
• choice of rational method and range of the control of speed of electric drive. That is depending on the technological terms of work of machines and mechanisms;
• choice of rational method of control of speed which depending on character of change of loading;
• increase of load of working machines;
• exception of the mode of idling;
• decline of tension on the clamps of engine;
• minimization of current and losses of the energy HELL at the change of loading;
• optimization of the dynamic modes;
• use of synchronous machine as compensates of reactive power;
• use of accumulators of energy.Fifth way is choice of rational type of electric drive for the concrete technological setting and transition from constitutive electric drive to adjustable one. In transition from constitutive electric drive to adjustable one it should be remembered that:
• it is often achieved the economy of energy not for the account actually of drive, and due to that process, which drive serves. Thus an economy can to excel in oftentimes own consumption of electric drive;
• for the receipt of useful power effect adjusting in very small limits at the limited requirements to quality of adjusting is often needed. So, only the insignificant adjusting of speed of pump which give hot water in building provides the substantial economy of expensive hot water. Such approach allows to use the cheap and reliable regulators of the tension tricked into to the puttees of stators of asynchronous engines in place of expensive and difficult transformers of frequency.Sixth way is improvement of quality of electric power by facilities of power converter technique of adjusting electric drive.
Adjusting electric drive during work renders unfavorable influence on the network of power supply, that is expressed in the decline of power-factor at the input of transformer, vibrations of supply pressure and distortion of sine form of tension.
The decline of power-factor increases reactive power of the system of power supply, that brings to the additional losses tensions over and energies and requires the increase of carrying capacity of its elements.
Nonsinusoid tension and current stipulates the additional losses and heating, and also speed-up senescence of isolation of electric motors, transformers and, in addition, negatively tells on functioning of different types of electrical equipment. Specific influence on different types of electrical equipment, systems of relay protection, automations, teleautomatics and connection shows up is differentiated and is depended on the peak spectrum of tension (current), parameters of electric networks and other factors.
Creation of high performance power electronic devices of the type IGBT, GТО and another allowed substantially to extend the functions of the power electronic devices which used for adjusting of quality of electric power. In the last few years standards with the hard requirements to quality of electric power are inculcated in industrial countries.
Traditionally for adjusting of quality of electric power thyristor stabilizers, compensates of reactive power and passive filters were used. A new element base of power electronics allows to create transformers of alternating/permanent current, working in the 4th quadrants of complex plane on the side of alternating current with impulsive modulation on the promoted frequencies (This term corresponds to a new standard MEK 60030551). It allows to operate the streams of electric power in any direction on the set law.
During connecting of stores of energy to the transformer from the side of direct current becomes possible to carry out an exchange by reactive power including power of higher harmonyc between the network of alternating current and store. Such chart lies in basis of most modern methods of adjusting of quality of electric power.
At vibrations of tension, is special in the low-powered (small currents of short circuit) electro-systems, there is the problem of their indemnification, as the high-speed devices of indemnification of reactive power are required in this case. In this case the effective decision of problem can be carried out by a new generation of the static thyristor compensating.
Seventh way is economy of electric power by working options and mechanisms due to the increase of efficiency of implementation of technological process. It includes the following basic measures:
• concordance of the modes of operations of setting at the change of loading;
• increase of CPD of setting;
• adjusting of productivity of setting;
• implementation of optimum mission profile and organization of the graph of loadings;
• providing of the rationed load (for lifting machines, conveyers and etc);
• control of the state of the technological setting;
• application of perfective aspects of electric drive;
• organizational measures.
