Vacon NX6, Design Manual

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7
vacon • 41 SIZING OF THE SYSTEM AND PRODUCT
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7. SIZING OF THE SYSTEM AND PRODUCT
The basic principles that have an effect on the power unit selection are described in this chapter.
7.1 Direct to DC
The energy storage voltage window sets up the guideline for the voltage class selection. The
maximum voltage sets the requirement for using either 500 V class or 690 V class units. The value
of DC High Ready (Stop) should be taken into account when choosing the appropriate unit with
adequate maximum voltage. If the storage maximum voltage stays below 800 Vdc, it is possible to
use 500 V class units. If it goes above 800 Vdc but stays below 1100 Vdc, the 690 V unit is applicable.
NX8 voltage class liquid cooled units can be used up to 1200 Vdc link voltage.
The minimum voltage of the energy storage is crucial in current dimensioning of the unit size. An
easy rule of thumb is that output voltage of grid converter is
The gain 1.56 is not accurate and depending for example on voltage drop in filters and grid state.
Theoretically the gain can vary from 1.41 to 1.89. However 1.56 is a good starting point.
Now if the customer has indicated the needed power P, the corresponding current I
ac
for calculated
voltage U
ac
can be calculated with:
The selection is made by choosing an appropriate current size from the VACON products with the
above defined voltage class based on the maximum storage voltage level. The output voltage is
needed for the transformer dimensioning.
230 V Unit 500 V Unit 690 V Unit Vac/Vdc
Supply voltage max 240 500 690 Vac
Supply voltage min 208 380 525 Vac
Over voltage instantly 437 911 1200 Vdc
Over voltage U2t trip - - 1100 Vdc
DC High Ready (Stop) 382 797 1099 Vdc
Normal Max 324 675 931 Vdc
Normal Min 280 513 708 Vdc
DC Low Run (Def.Estim.) 242 475 656 Vdc
DC Low Ready (Stop) 239 436 602 Vdc
DC Low Running Min 225 410 567 Vdc
Under voltage instantly 183 333 461 Vdc