Gene Heskett wrote: > On Sunday 04 January 2009, Jon Elson wrote: > >> Gene Heskett wrote: >> >>> Interesting. The length of the radial portion of the bearing must be >>> fairly short then? >>> >> The radial bearing sections are about 3/4" long, I think. These are >> combo hydrostatic/hydrodynamic bearings. >> I once had a hose blow off while drilling a hole, and waited until the >> drill was out of the hole to pause EMC and shut off the motor. >> It seemed to spin down pretty normally without the bearing air. >> >> > I'd have assumed the 'hydrodynamic' would have held it properly even without > pressure at that rpms, allowing contact and drag only when it had slowed > considerably. > Yes, exactly. > [...] > >> > I wonder if a triplet of stepdown transformers would more properly match the > vfd's current abilities to that particular motors requirements? A 2/1 ratio > might be worth a try just for grins. That might require a minimum speed > setting to prevent core saturation in the iron though, as allowing that would > be pretty hard on the vfd. With typical iron from Herbach & Rademan, not > less than 50 hz for a low limit should prevent that. > Yes, but they'd have to be designed for a wide frequency range. If I could get the VFD to go to 1000 Hz, then I'd need 200 V RMS output, so you couldn't use a step down. Limited to 400 Hz, I can't go over 80 V RMS, so I suppose I could, but what I have works. I put a fan on the VFD. I doubt 4 A RMS will hurt a VFD rated for 3.3 A continuous. I did put an inductor in series with each motor leg to reduce the ripple current.
Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
