The Vfd And Related Problems; Figure 14 - User Connection To The Interface M3 Terminal Boards - Daikin EWYD-BZ Series Installation, Maintenance & Operation Manual

Figure 14 - User connection to the interface M3 terminal boards

Unit basic connections
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The VFD and related problems

The units described in this manual use a VFD (Variable Frequency Driver) to vary the compressor rotation speed and
consequently the refrigerant charge generated, maintaining the efficiency of the compressor itself at extremely high
levels compared to other methods of capacity unloading.
Fig. 12 illustrates the power absorbed by a typical single-screw compressor, depending on the load developed by the
compressor, in the classic solution of unloading using slides and with speed variation
Notice how the input power is always lower (by up to 30%) in the case of speed variation compared to the use of
unloading slides.
Furthermore, in the case of speed variation, the compressor can rotate faster than its nominal speed and thus develop a
load greater than 100%, which is obviously impossible with a fixed speed rotation, thus recovering loss in capacity due to
unfavourable environmental conditions, such as low ambient temperature.
Additional
expansion for
Heat Recovery
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Additional expansion for Additional expansion for water
pump control setpoint reset and Unit limitation
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