Change the speed of the motor shaft by means of electronic device, which is usually called a frequency converter. Speed control is done by changing the frequency and amplitude of the three-phase voltage supplied to the motor. In this way, changing the parameters Supply voltage (frequency control) can control the speed of rotation of the motor, installing it, both below and above par. The method of frequency control is a simple principle. Frequency industrial network, as a rule, is 50 Hz. For example, we use a pump with a two-pole motor. For a given frequency, rotational speed of the motor will be 3000 rpm (50 Hz x 60 sec.).
At the same time on output we get the nominal head, and the performance corresponding to the passport unit. Using a frequency converter, we can reduce the frequency of applied ac voltage and, consequently, change pressure and the performance of the pump. The frequency converter changes the frequency accordingly, based on a special pressure sensor that is installed in the pipeline. Modern Frequency Converters are compact size, simple interface (there is already a Russian language version), the body that prevents dust and moisture, so their application is possible even under difficult climatic conditions and in moderately aggressive environments. Range of the market represented a wide power range from 0,4 to 500 kW or more at a standard power 220/380 V, 50-60 Hz.
We will not go into a detailed review of charts and cycles of pumping installations with frequency inverters, but only give some information for thought for those readers whose sphere of activity is somehow linked to the functioning of public utilities. Often decision-makers to upgrading equipment, examining the cost of introducing frequency converters, postponing a decision indefinitely, without realizing the long-term benefit of the whole project. In fact, every implementation requires economic evaluation. And, of course, the majority of qualified engineers are able to conduct relevant feasibility study. The more so because the market is saturated with enough converters and has a wide horizon price, depending on the functionality of devices and brands. Proved that the use of frequency converters in pumping stations allows: – to save electricity, due to the organization of the electric drive in Depending on the actual consumption of water (the effect of saving 20-50%) – reduce water consumption by reducing leakage occurring at an elevated pressure in the line, when water consumption is really low (an average of 5%) – reduce the costs of routine and major repairs of buildings and equipment (the whole infrastructure of water supply), resulting in suppression of emergencies caused by a particular hydraulic shock, which often occurs in the case of unregulated electric (resource service equipment increased at least 1.5 times) – to reduce the payroll service and staff on duty through a comprehensive automation of water systems – to achieve some savings in heating systems, hot water by reducing water losses, which carries the heat – if necessary to make the pressure higher than usual. Practice shows that in majority of projects on the introduction of frequency converters recouped in 1-2 years. And what result you got?