On 11/25/2014 02:43 PM, Viesturs Lācis wrote: > Hello! > > I need to drive 2 high-speed spindle motors, 3,7 kW each. For that I > have 11 kW VFD. > The problem is that I attached motors to the drive, tried to run them, > but VFD does not increase frequency above 8-9 hertz (all the default > frequency values are 50 hertz, I checked them and set to 100 to make > sure that it not a problem). And in addition to that motors get really > hot in a minute or so. I set "no load current" to 0,2 A, max current > currently is set to 17 A (max current for each motor is 8,7A). You need to set the V/Hz slope in the VFD's settings. Every motor has some V/Hz curve, which is usually a straight-line slope. Different VFDs have different ways of making this setting. For instance, on a particular air bearing spindle motor I use, it wants 80 V at 400 Hz.
The other thing is high speed motors have very low inductance. On that particular unit, I needed to add 1 mH inductors in series with all 3 motor wires. > This VFD worked fine few weeks ago with 7 kW motor. I checked the > motors today with 2kW VFD - worked just fine. > > Ok, I can decrease max current to 2-3 amps, while testing, probably > that should fix the overheating, but why does it not allow to increase > frequency? > > It is probably getting stuck at low speed due to high current. The larger VFD may have a lower PWM frequency, which is causing the peak winding current to exceed the current limit. it suppresses frequency increase, waiting for the motor to "catch up" and current to go down, which never happens. So, it gets stuck. Sounds like the inductors may be required. Jon ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=157005751&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
