The use of Danfoss frequency converters in the power circuits of centrifugal mechanisms can significantly save energy consumption. In mechanisms of this type, the consumed energy is proportional to the cube of the frequency of the supply voltage of the drive. Consider, for example, a D500-65 pump drive powered from the mains through a frequency converter. If you reduce the frequency of the supply voltage from 50 to 40 Hz, then the energy consumption will decrease by:
(40/50) ³ = 0.512,
i.e. 2 times.
The main characteristic of a centrifugal mechanism (pump, compressor, centrifugal fan) is the performance-head relationship of the mechanism. As a rule, for each model of the unit, there are graphs of the dependence of the head H on the productivity Q for fixed values of the speed.
When calculating, it is important to take into account the characteristics of the hydraulic lines on which the pump is used. To do this, it is necessary to plot the characteristic of the hydraulic line and the pressure characteristic of the pump on one graph. The pump operation mode in this line is set by the point of intersection of both graphs.
The pressure can be controlled either by throttling the line or by frequency control of the pump. As practice shows, throttling is quite uneconomical, since it increases the hydraulic resistance and spends a lot of pump power to overcome it.
Frequent regulation of the pump drive motor allows optimal performance adjustment. This ensures maximum energy savings and gentle operation of the equipment and reduction of loads of various kinds. As a result, the service life of the equipment is extended, sometimes several times, and the cost of repairs is reduced. With this control method, the pressure in the system is kept constant at different flow rates, the output characteristics change smoothly. This also prevents water hammering in the system.
Calculation of the payback period from the introduction of frequency management depends on two factors:
1) Electricity tariff. The cost of electricity depends on the category of the consumer organization.
2) Equipment type. The rule applies here - the more powerful the unit, the less time it pays for itself. This is due to the specific cost of the frequency converter. With increasing power, it decreases. In some cases, the introduction of frequency regulation on low-power equipment can quickly pay off, provided there is a high energy-saving potential.
Despite the high cost of implementing this technology, in the future it quickly pays off due to the positive factors listed above. As a rule, wed
