Page 577 - Mechanical Engineers' Handbook (Volume 2)

568 Servoactuators for Closed-Loop Control

Table 6 Stepper Motor Specifications (Crouzet Model 82940.0)
Step angle 7.5
Number of phases 2 (bipolar)
Resistance per phase 9
Inductance per phase 24 mH
Current per phase 0.55 A
Maximum input power 10 W
Maximum voltage 6.7 V (continuous duty)
Holding torque at 6 V 21.9 in. oz
Detent torque 1.67 in. oz
2
Rotor inertia 1.19 10 3 in. oz s /rad
Maximum coil temperature 248 F

T friction torque on viscometer cup
ƒ
˙ m motor shaft speed
From the specifications and Eq. (33): d /dt 78.5 rad/s and T 14.2 in. oz (0.10
2
m
m
N m). From the torque–speed characteristics of Table 6 it can be seen that the characteristic
labeled b can be used. So a series resistance of 9 should be used to meet the torque
requirements.
The electrical and mechanical time constants may be estimated as follows:
L
2.7 10 3 s
e
R
J J
m L 5.3 10 3 s
m
B L