Page 565 - Mechanical Engineers' Handbook (Volume 2)

556 Servoactuators for Closed-Loop Control

Figure 9 Cross section of a brushless dc motor. (Courtesy of Moog, Inc., East Aurora, NY.)

Numerical Example
Table 5 shows the specifications for a ceramic magnet, inside rotation-type dc brushless
motor manufactured by Magnetic Technology. 14,15
If this motor is operating at peak torque, the steady-state motor speed is given by [from
Eq. (4), dropping the dynamic terms]

Table 5 Performance Data for Magnetic Technology Model 2800-153-084 Brushless dc Motor
Peak torque 40 in. oz
Power at peak torque 175 W
Electrical time constant 0.0005 s
Mechanical time constant 0.054 s
Damping factor 0.064 in. oz s/rad
2
Moment of inertia 0.0035 in. oz s /rad
Total breakaway torque 1.5 in. oz
Temperature rise 2 C/W
Maximum allowable winding temperature 155 C
Weight 19 oz
Number of poles 8
Number of phases 2
Resistance 8.4
Inductance 4.2 mH
Voltage at peak torque 38.2 V
Current at peak torque 4.57 A
Torque constant 8.7 in. oz/A
Voltage constant 0.0617 V s/rad