DC voltage bus, often applied to drive controllers

Question:
What advantages do inverters with DC voltage bus have for the operation of rotating field machines compared to inverters with DC current bus?

Answer:
v-inverters (drive controllers with DC voltage bus, e. g. 8200 frequency inverter, 9300 vector or 9300 servo drives or L-force 9400 Servo Drives and 8400 Inverter Drives):
Advantages, especially for a wide field of application:

• They do not take much space and
• they are suitable for a highly dynamic current control (especially important for servo features).
• Moreover, the supplied mains is only slightly loaded with reactive power (harmonic reactive power). Line faults have a less negative effect on the drive behaviour, as if the drive controllers would be synchronised directly to the mains (e. g. thyristor controlled current controllers).

DC inverters:
Description:

• In comparison to the v-inverters they have a lower dynamic due to the great inductance (therefore, it is less suitable for dynamic drives) and
• need much space and have much weight due to the required inductance (choke).
• They are applied in case of a higher power range (some MW), e. g. wind energy plants, as due to the controlled input bridge (SR1) the possibility of rectifying is easier to realize.

Direct controller:
It would be perfect, but there are no suitable components on the market, which can work as bidirectional switches (the solution with interconnection matrix with 18 single switches is expensive, the drive is complex, problem of different gate potentials...). Currently there are different university development projects, as this solution could bring an important innovation to the drive technology.

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