Hiho
Thank you for your considered response.
Re the contentious subject of cogging.
Coreless motors cog, as accidentally powering up a Goldmund Studio without its platter, clearly demonstrated. ( JVC 4 pole, 2 phase, coreless motor). It was a dumb thing to do, but informative never the less.
The problem that you rightly ascribe to the SP range is not IMO cogging.
It is way too high in frequency to be so. The motors have 15 stator poles, don't know how many mag poles, but some higher number.
Making around the mid 200 HZ of power pulses per revolution. But they are 3 phase motors, each phase separated by 120 degrees. The sinusoid supplied phases slide into each other, improving linearity considerably, so "power pulse" would seem to be the wrong term to use.
The SP10s higher pole and phase count than a number of coreless DD motors, would imply, for a given output torque, lower amplitude but higher frequency cogging.
( The motor only delivers the torque asked of it under the load conditions at that moment in time). If it delivered higher torque than the load demand, the platter would accelerate.
I hear the problem in a standard SP10 in the kHz range. This is a feedback speed sense issue and is not intrinsic in the motors architecture and any cogging that it may produce.
It can be fixed.
Thank you for your considered response.
Re the contentious subject of cogging.
Coreless motors cog, as accidentally powering up a Goldmund Studio without its platter, clearly demonstrated. ( JVC 4 pole, 2 phase, coreless motor). It was a dumb thing to do, but informative never the less.
The problem that you rightly ascribe to the SP range is not IMO cogging.
It is way too high in frequency to be so. The motors have 15 stator poles, don't know how many mag poles, but some higher number.
Making around the mid 200 HZ of power pulses per revolution. But they are 3 phase motors, each phase separated by 120 degrees. The sinusoid supplied phases slide into each other, improving linearity considerably, so "power pulse" would seem to be the wrong term to use.
The SP10s higher pole and phase count than a number of coreless DD motors, would imply, for a given output torque, lower amplitude but higher frequency cogging.
( The motor only delivers the torque asked of it under the load conditions at that moment in time). If it delivered higher torque than the load demand, the platter would accelerate.
I hear the problem in a standard SP10 in the kHz range. This is a feedback speed sense issue and is not intrinsic in the motors architecture and any cogging that it may produce.
It can be fixed.
