Brushless PM Motors

Providing the highest mechanical power output and torque per unit volume, the Brushless Permanent Magnet Motor (BPMM) is the workhorse of the motor line family. These high performance motors require an integral motor rotor position indicator in order to maximize motor performance and operation.<br><br>The rotor is constructed with durable rare earth samarium cobalt magnets for high temperature performance, stability, and durability. The electrical windings are on the outside stationary stator, providing minimal thermal resistance between the windings and the motor case.

Description / Applications: Rotary Accelerometers (RA's) provide a DC output voltage in proportion to the rotary acceleration of the motor shaft. These permanent magnet devices require no excitation or input power. Ra's are ideal components to achieve a higher order servo stability performance characteristic. The acceleration signal may be used alone, or the voltage may be integrated to provide velocity plus acceleration information. Feedback can eliminate limited cycle oscillation in geared servo systems, and allow high forward loop gain through response shaping networks (PI or PID) in digital or analog signal processing networks. See Page 23 for a Functional Block Diagram or a Rotary Accelerometer in a Close Loop Servo Application.

RA’s may also be used in stepper motor applications, to determine the torque null “crossover” of the motor rotor during operation. This information is useful to determine optimum stepping pulse rate in high load inertia applications, or the stepper motor pulse rate may be dynamically controlled to step at the crossover point, allowing the motor to operate at the higher efficiency slew region of performance while maintaining step count. Since the permanent magnet RA provides a direct DC signal, the output may be used to determine step to step integrity of the stepper motor in critical pointing mechanisms where step integrity is paramount. See Page 22 of our Stepper Motor Engineering Reference Data brochure for additional information on RA benefits with stepper motors.

Imperial Units
Type Output Voltage Output Load Added Length Accelerometer
Added Inertia Added Weight
V/100kRAD/sec² Ohms Inches Inches Oz-In-
03ACC 0.60 50000 0.575 0.750 2.8 E-06 0.750
05ACC 2.1 50000 0.575 1.250 5.5 E-05 2.0

Metric Units
Type Output Voltage Output Load Added Length Accelerometer
Added Inertia Added Weight
V/100kRAD/sec² Ohms mm mm kg-m² kg
03ACC 0.60 50000 14.6 19.1 2.0 E-06 0.021
05ACC 2.1 50000 14.6 31.8 3.8 E-07 0.056