15hp Vfd

[Jager]

Hi,

I've been looking into buying a VFD. Most of the ones I've seen come with a fused disconnect. However, I've seen one manufacturer that offers a circuit breaker.

I would think that a circuit breaker would be better, because it's easier to reset. My question is, what are the advantages of using a fused disconnect for feeding VFDs? Why does every manufacturer but one use them?

Thanks in advance

 

[RayS]

Lower first cost would be my guess.

There used to be a need for semiconductor (fast acting) fuses for some types of power semiconductors, but it seems to be less of an issue now.

 

[robbietan]

the VFDs use fuses since they trip faster than breakers. the semiconductors in the VFDs are very sensitive to fault/inrush currents.

and they can use fuses direcly on their pc boards.

 

[petersonra]

Hi,

I've been looking into buying a VFD. Most of the ones I've seen come with a fused disconnect. However, I've seen one manufacturer that offers a circuit breaker.

I would think that a circuit breaker would be better, because it's easier to reset. My question is, what are the advantages of using a fused disconnect for feeding VFDs? Why does every manufacturer but one use them?

Thanks in advance

VFDs packaged together with a disconnect are a semi-custom item. Normally the VFD comes by itself and the other stuff gets added. A shop can make you any combination of things you want in one box.

We rarely use CBs strictly because of the cost difference. Some customers want the capability of just resetting it if it trips rather than chasing all over the place at 2:00 am looking for spare fuses.

Common things we add to base VFDs:

- switches and lights
- pots
- bypass contactors (not as common any more though)
- fans
- PLC I/O
- disconnects (fuses or CBs)
- comm modules
- A/C (sometimes vortex coolers)


Boxes can be anything from cheapest NEMA 1 sheet metal, to NEMA12/13, SS, FRP, whatever someone wants.