gene heskett wrote: > > > Bring in the VFD, and of course you are right. The VFD may in fact have > more amps per leg flowing but with careful design, can recover much of that > which isn't actually used to turn the motor, I've seen that in the > discussion so far. > > Which leads me to believe that the VFD's enhanced efficiency would pay for > itself in reduced power draw over time. > > No, the VFD does not reduce POWER consumption as long as the motor is run at rated speed. You can reduce power consumption quite a but by running fans and pumps at reduced speed, instead of using louvers and valves to throttle the flow.
Reducing line current is not the same thing as reducing POWER. Induction motors can often draw current close to the rating all the way from idle to full load, but the power drawn varies, due to the changing phase angle. An inductor plugged into the wall socket may draw 15 A of reactive current, but since it is at 90 degrees to the voltage, there is no real power, so the electric meter doesn't register it. It only reads real power, ie. current that is IN PHASE with the voltage. Now, if your electric utility bills you for power factor, that is an entirely different situation, and all large power consumers are either billed or periodically audited for power factor and peak usage. Our university is billed at a flat rate for an entire year based on the highest 15 minute period of the previous year! Thus, peak load control is a big issue, and saves them millions of Dollars a year. I don't know what they do about power factor, but I'm sure that is something they control, also. Jon ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
