The VFD is an old EMS G3+ (Yaskawa) drive. The old motors were 200-240v(or 380-460v), 18,000rpm, 7hp. When running the old motors they were drawing about 5-7amps when running at 300Hz. The new motor's tag says 380v, 18,000rpm, 6kw and when running with the VFD set to 300Hz shows about 2 amps current draw. The first test cut with a 1/4" down spiral through two layers of 1/4" MDF (200ipm feed) has no audible drop in rpm, and the VFD shows about 2.5 amps. I think it looks good enough for me.
----- Original Message ----- From: "Karlsson & Wang" <nicklas.karls...@karlssonwang.se> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Sent: Tuesday, November 3, 2015 11:15:33 AM Subject: Re: [Emc-users] Spindle Voltage? > On Tue, Nov 3, 2015, at 09:41 AM, Todd Zuercher wrote: > > I recently purchased an inexpensive router spindle off of ebay. It is rated > > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and > > could be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't > > think to check the old VFD and it is only capible of low voltage (running > > 208 3ph). > > > > So my question, what are the repercussions of feeding this motor with only > > 208 3ph? > > > > If the only problem is a loss of a percentage of power, but not more than > > half, I can live with that. (It cost less than 1/3 the price of the > > original.) > > > > If you keep the same voltage-to-frequency ratio and maximum current the motor > will be happy. > But of course the speed will be lower. For example, if it is designed for > 380V, 240Hz, 14,400RPM, > the volts-per-hertz ratio is 380/244 = 1.5833. If the VFD can only deliver > 208V, then you will be > limited to 208/1.5833 = 131Hz, and the top speed will be 7860 RPM. It will > still deliver rated torque > at rated current, but since the speed is lower the kW will be lower - only > about 3.8kW. > > You can run it at a lower voltage-to-frequency ratio, but you won't get the > same torque. For example > you could run it at 208V and 240Hz. You would get a no-load speed of > 14,400RPM, but the torque- > per-amp will be lower - you'll still only get 3.8kW. > > > -- > John Kasunich > jmkasun...@fastmail.fm I agree. To keep voltage-to-frequency ratio up to the maximum voltage and then just increase frequency is probably the best. The VFD may use space vector control instead of voltage-to-frequency ratio. Did you double check if your motor is Delta connected and may be Y connected instead? Nicklas Karlsson ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
