tailieunhanh - Industrial Brushless Servomotors Episode 6

Tham khảo tài liệu 'industrial brushless servomotors episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Brushless commutation 95 and eight-pole motors as the rotors turn through 360 mechanical degrees. The figure also shows the signal which originates from the resolver for the sine of the mechanical angle of the rotor. The drive converts the mechanical angle determined from the resolver signals into the electrical angular position required for commutation according to the number of rotor poles. The motor-sensor combination There are two types of brushless motor and several types of sensor giving many possible combinations. The combination used in practice is chosen partly according to its costeffectiveness for the application in hand. The choice is also affected by the potential scale and future development of the application. Sinusoidal drive systems are generally more expensive than the trapezoidal type and there is a great difference between the price of an absolute and an incremental encoder. In general the least expensive sensors are used with trapezoidal motors. Trapezoidal motor-Hall-effect sensor The speed of the trapezoidal motor can be estimated by using the signals from the Hall-effect sensor already fitted for the purpose of commutation. The signals are too widely spaced to be used for position control but speed regulation above about 500 rpm is possible. The method is limited mainly to on-off fixed speed applications one example being the brushless industrial fan motor. In this example the rival pricewise is the induction motor and inverter unit. Trapezoidal motor-tacho and incremental encoder The shaft speed sensor of the trapezoidal motor is normally in the form of a tacho and an incremental encoder is added when 96 Industrial Brushless Servomotors measurement of the shaft position is required. The encoder output can be processed to give a measurement of motor speed but the resulting signal is not usually good enough at the mid to low end of the range. This is due to the presence of a ripple which is inversely proportional to speed. The ripple