AC inverters on a common DC bus?

If you *really* want to do it this way, I too would recommend the Siemens

You didn't state what motor size you are talking about (reel unwind does not necessarily equal small), but if they *are* small, the cheaper way to do it would be to use seven "bookshelf"-style drives the likes of Danfoss, SEW or PDL (not in any particular order) and common-up the AC inputs. Below a certain drive size, there is no benefit in splitting out the inverter part.

Cameron:-)

Oh, sorry, you did! - "fractional horsepower". My second comment still applies. :-)

Cameron:-)

Almost all drives have an accesible DC link. I can't see a problem with interconecting these links (via fuses) so that drives in regeneration can supply power to drives in motoring mode. It may be advisable to install a braking resistor as well.

It depends upon what kind of DC bus protection the drives use.

To reduce the cost of the drive (and to prevent people electrocuting themselves), some of the smaller drive manufacturers ('fractional horsepower') deliberately do NOT have the DC bus available (that's one reason Masterdrives are so expensive).

Remember that DC bus volts can get up near 1kV on regeneration, so if the DC link is available you need to be *really* careful how you design, select and install DC bus isolation and fusegear - your average DC bus capacitor is blooming huge and contains enough energy to run the motor for several seconds on power failure!

At the end of the day, it depends exactly which brand/model of drive the OP gets and that will depend upon what is available to him. Certainly, if he is going to do this it would be a good idea to install a braking resistor - and one sized large enough for the duty.

Cameron:-)