VECTOR CONTROL AND MOTORS 8-5
SB1391 Hardware and Setup Guide - Document revision no. 1.14
If a high performance servo system is required, but not the high dynamic characteristics of
a DC brushless (AC servo/AC synchronous) motor. When the inertia of the load is much
higher than the inertia of the motor (and it may be difficult to match the inertia of the load to the
inertia of the motor). In such cases, a significant cost reduction can be realized by using an AC
induction motor.
When high accuracy, low velocity control is required. The high inertia of the AC induction
motor and the ability to eliminate most of the magnetic field cogging, will help in overcoming
low frequency disturbances, thus achieving a better velocity regulation. Better than an DC
brushless (AC servo/AC synchronous) motor based servo!
When motor without brushes is required and there is no budget for a DC brushless (AC
servo/AC synchronous) motor. It is surprising what smooth performance and how much torque
a small, low cost AC motor can generate. Usually an AC motor is specified by its power level and
nominal speed. For example, a 1.1KW motor @ 1500rpm nominal no-load speed. A motor like
this (assuming 100% efficiency) is capable of generating rms torque of 7Nm at 1500rpm and
15Nm peak torque at lower speeds!
If using a motor to its full power specifications, make sure that it is cooled by forced air.
Otherwise de-rate it by 35-40%.
The motor's windings should be arranged in delta configuration.
The setup procedure for an AC motor differs from the setup procedure for a DC brushless (AC
servo/AC synchronous) motor only in the commutation adjustment. All other adjustments are
identical. Once the control unit is adjusted properly, it is completely transparent to the user what
type of motor is being used.
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