Fused VC Vs VCB for Motors
Fused VC Vs VCB for Motors
(OP)
Have been looking at a SLD, wherein it is mentioned to use VCU for Motors below 1.5MW and Circuit breakers for above 1.5MW for MV applications (11kV).

I know that contactor ratings are available at 400A & 800A.
Any reasons for using circuit breaker?

I know that contactor ratings are available at 400A & 800A.
Any reasons for using circuit breaker?
RE: Fused VC Vs VCB for Motors
RE: Fused VC Vs VCB for Motors
Thus, though the contactor is rated at 400A, it is the stability of fuse during motor starting that decides what should be the desirable maximum rating of motor.
The magnitude of motor starting current as well as the duration plays a critical role.
RE: Fused VC Vs VCB for Motors
There is also a difference in the vacuum bottles used. Contactor vacuum bottles are designed to reduce “chop current” on opening, which can damage motor windings. The metallurgy of the contact material is optimized to minimize this, but that reduces its ability to handle high interrupt current, hence the need to be paired with fuses. VCB vacuum bottles are usually not designed for reducing chop current because their main function is protective, not control. The metallurgy in the contacts is tailored to handle higher interrupt current, not chop current, resulting in the chop current typically being 5x that of a VC. If you are not cycling a motor on and off very often, that’s not as big of an issue.
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