On 25 February 2012 10:15, andy pugh <bodge...@gmail.com> wrote: > The back-emf in any particular field winding will be independent of > the current, but the field windings which are driven by the H-bridge > at any one time will be different between a properly commutated bldc > with a 90 degree phase shift and one being driven effectively as a > low-pole-count infinite-microstepping stepper motor.
Thinking further, whilst I think the above is correct, a bigger effect might be that a VFD runs at a fixed current and a speed-controlling PID in LinuxCNC can only vary the frequency (which increases torque at a constant load speed in an induction motor, but doesn't in a synchronous motor, which can only lose synch if drive frequency and spindle speed don't match). In the case of a bldc drive the PID loop varies the current (and it will typically be low at low load) and the field is always in synch. -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
