On Wed, 28 Apr 2010, Jon Elson wrote: > Date: Wed, 28 Apr 2010 11:16:14 -0500 > From: Jon Elson <el...@pico-systems.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Microcontroller motor drive [Was: Resolver to > Quadrature Convertor] > > Andy Pugh wrote: >> I just found this application note from Atmel >> http://www.atmel.com/dyn/resources/prod_documents/doc2592.pdf >> > The problem with all of these designs is they have no current loop > control. I could be wrong, but I think you really need closed-loop > current (torque) control for this to work well. If you do this in > voltage-mode control (just adjusting the PWM duty cycle without sensing > motor current) then I think you will find that the loop becomes very > hard to tune near zero speed, where the requirement for PWM duty cycle > will be VERY low. This is how my drives work, but since they are only > doing trapezoidal drive, you don't have to impose the sinusoidal drive > waveforms on top of that already small pulse width. > > Jon >
We've (and our customers) have run motors in sinusoidal voltage mode with our 7I39 with good results for many years, so it is possible. Its tougher with IGBTs than MOSFETS since the IGBT deadtime is a so much greater proportion of the total on time. This requires good deadzone compensation so the actual motor voltage is more linear near zero (The pulse width is ~50% at ~0 voltage, its just the overlaps that get small) Voltage mode actually has some advantages over current controlled mode: Better inherent high frequency damping (driver has low impedance) Quieter (Current control loops invariably hiss and whistle) balanced with some disadvantages: No torque limit/control other than overall current limit Lower bandwidth (inductance feed forward can help here) Peter Wallace ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
