Power, voltages and transformation ratio
Rated power
For transformer ratings under 10 MVA, IEC 60076-1 suggest preferred values based on the R10 series1: 10, 12.5, 16, 20, 25, 31.5, 40, 50, 63, 80, 100, and multiples of 10n. For example, the preferred transformer sizes from 500 kVA to 4000 kVA are: 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000.
Voltages at higher voltage (HV) side and lower voltage (LV) side
ABB claims that the VSD supply transformer is usually fed by a medium voltage network, but sometimes the transformer primary voltage may be at the LV level. Feeding from an HV network is also possible but rare. The input voltages in MV drives are from 1 kV to 36 kV. The input voltages in LV drives are usually between 380 V and 900 V, depending on the drive type".2
In DriveConstructor it is possible to choose not exact values but ranges of values.
Voltage (HV)
The ranges can be chosen from the following: 2200-2500, 2500-2800, 2800-3200, 3200-3400, 3400-4100, 4100-4300, 4300-5800, 5800-6800, 6800-9000, 9000-12000 V. Choose range which fits grid voltage. Default setting is «any».
Voltage (LV)
The ranges can be chosen from the following: 380-440, 650-700, 2400-2500, 2900-3100, 3200-3400, 4100-4200, 5900-6700 V. Choose range which fits FC voltage. Default setting is «any».
Transformation ratio
In DriveConstructor the ratio is defined by the ranges chosen for the grid side (MaxHV-MinHV) and FC side (MaxLV-MinLV) and the additional adjustments made manually (see the software). The range of ratios is:
- minimum ratio is calculated as MaxHV/MinLV,
- maximum ratio is calculated as MinHV/MaxLV.
Then the ratio can be "manually" adjusted within the range between minimum and maximum values.