Also be aware there are two types of brushless servo motors and drives, Sometimes refered to DC Brushles and AC brushless, there is basically very little between the construction of either motor, the difference comes in the type of commutation, DC brushless uses hall effect sensors to sense the armature position and the amplifier produces a series of pulses at the right moment to drive the rotor, the AC servo has more of a true sinusoidal drive and obtains rotor feedback via an encoder or resolver, the average torque of a DC brushless is about 5% lower than an AC brushless the peak torque however is around 10% higher.
One downside of the DC brushless is that it appears more like a stepper at low rpm, due to the pulse effect into the winding, whereas the AC servo is smooth down to very low rpm. this explanation is a bit simplistic but there is alot of infornmation on the various vendors web sites on this subject.
Al
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.