Hey Jeff, The concept of running a "buffer" motor in parallel was on my mind, but I wasn't sure what parameters I needed to be concerned about while trying to specify it. I'll look into building such an beast given what you've suggested. You don't happen to know of any companies that sell "off-the-shelf" type units? I haven't been able to find such a beast yet despite several hours spent on google.
Thanks to everyone who has responded on this topic. We've now graduated to a a transformer/phase converter solution (from our utility supplied power), but we're still having the same problem. Darcy -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Jeff Condit Sent: January 4, 2006 8:40 AM To: Open Topic Forum Subject: Re: [OT] PCB router Just a thought: They make 3-phase motors with large flywheels for surge buffering. This is wired in parallel with the power source (generator) and is physically separate from the real motor you want to use. It runs continuously and uses very little power even though it is a similarly sized motor because the flywheel offers no running load. The purpose is to buffer the line voltage during surges and handle large intermittent currents. When you turn your vacuum motor on and the voltage just starts to dip a little, energy stored in the flywheel is converted through back-EMF to 3-phase current (synchronous with the source) pushed back onto the power lines to bolster them up. They are use in many industrial applications where peak loads are very short and high compared to the average. The buffer motor rating should be equal to or higher than that of the vacuum motor, and the flywheel momentum must be sufficiently large to not slow down significantly during the startup surge. If you estimate the startup energy required for the vacuum motor (volts x amps x time), the stored rotational kinetic flywheel energy should be about ten times larger. Jeff Condit ----- Original Message ----- From: "Alfonso Baz" <[EMAIL PROTECTED]> To: "'Open Topic Forum'" <[email protected]> Sent: Sunday, December 18, 2005 1:02 PM Subject: RE: [OT] PCB router > Darcy, > > The 5hp motor is around 3.7W at no load start-up current would be around 6 > times the full load current, which in this case is around 107A (208V). > Your 20kw alternator would be rated at around 96A. > The alternator's irons shouldn't saturate at the 107A but the rather > abrupt > current drawn will produce a voltage dip. > The only way around this with the gear you have, if you're lucky, is to > see > what adjustments are available on the AVR. Most decent AVR's have at least > 2 > adjustments, response time, and stability. If you can get the AVR to > respond > quick enough you might get the voltage dip to lessen in it's severity but > you could end up with an alternator who's output voltage hunts. Another > problem you'll run into is the engines governor and the power rating of > the > engine. If the engine is weak compared to the load you are placing on it > then no matter how fast the governor responds the engine will not be able > to > keep up the revs and thus the frequency dip will also upset any electronic > controllers on the router. > An alternative to buying a larger alternator might by to by another > alternator and run it in parallel. With this set up though you will need > some kind of syncroscope to bring the 2 alternators on line and the avr's > should also have droop control so that you can keep a lid on circulating > currents (Power Factor or cos phi). > I believe the cheapest alternative would be to replace the motor with a > single phase one until you get 3 phase installed and the get the existing > motor/s rewound to what ever is the standard 3 phase voltage there (415V > in > Oz) going to a higher voltage will reduce the current drawn by the motor > but > you might have to upgrade contactors etc to handle higher voltages > > Regards, > > Alfonso > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Darcy Davis > Sent: Saturday, 17 December 2005 11:10 AM > To: [email protected] > Subject: [OT] PCB router > > Hey Guys, > > We've found ourselves in somewhat of a bind. We've got a PCB router in > house > which is powered from 3-phase 208V. Its a very, very long story, but its > going to be 10wks till our utility supplies 3-phase power. Currently we > have > 240V single phase power, so I've looked into a phase converter but we > still > need to bring the voltage down to 208V. The other option we've been trying > is to use a generator. Turns out that when the 5hp vacuum motor fires up, > the generator doesn't respond quickly enough to counteract the effect, so > we > suck the voltage (and frequency) through the floor. This of course causes > the motor controllers to complain. We've got a 20kW generator already (for > a > ~4kW load), so I don't think a bigger generator will fix the problem. Is > there another way around this with a generator? (Ie, could we try to run > the > controllers from a UPS or will we kill the UPS?) If we were to run a > 3-phase > motor load continuously while we run the router, would it tend to buffer > the > effect? Power systems is well out of my league, so any comments you have > would be welcome. > > Thanks, > Darcy Davis > Design Engineer > > ========================================================= > Dynastream Innovations, Inc. Ph: (403) 932-9292 ext. 132 > 228 River Ave. Fax: (403) 932-6521 > Cochrane, AB T4C 2C1 Web: www.dynastream.com > Canada > ========================================================= > > > ____________________________________________________________ > You are subscribed to the OT discussion forum > > To Post messages: > mailto:[email protected] > > Unsubscribe and Other Options: > http://techservinc.com/mailman/listinfo/ot_techservinc.com > > Browse or Search Old Archives (2001-2004): > http://www.mail-archive.com/[email protected] > > Browse or Search Current Archives (2004-Current): > http://www.mail-archive.com/[email protected] > > > > > > ____________________________________________________________ > You are subscribed to the OT discussion forum > > To Post messages: > mailto:[email protected] > > Unsubscribe and Other Options: > http://techservinc.com/mailman/listinfo/ot_techservinc.com > > Browse or Search Old Archives (2001-2004): > http://www.mail-archive.com/[email protected] > > Browse or Search Current Archives (2004-Current): > http://www.mail-archive.com/[email protected] > > ____________________________________________________________ You are subscribed to the OT discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/ot_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected] ____________________________________________________________ You are subscribed to the OT discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/ot_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
