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this optimal rpm value both power output and efficiency proceed to decrease.
From the dynamic measurements, we can conclude that there is a small value of
viscous damping and that this value increases when breaking load is applied. This viscous
damping variable can be attributed to losses in the bearings, and eddy current losses in
the magnetic materials.
An assumption made in the model of the dynamic mechanical part of the DC
motor was that the electrical time constant te is small so the current in the motor reaches
its steady state value before the motor starts to move. Based in our calculations we can
verify that this is the case, since te is 0.007 with no disk and 0.009 with the disk. Along
with this observation, we note that the presence of the disk affects the performance of the 20 motor by increasing the value of all time constants, te, ts, and tm. Thus, when the disk is
incorporated to the apparatus, it takes a little longer for the motor to reach 63% of its
steady state value, including it steady state current and steady state angular velocity. 8. References
Akbari, Pejman. “DC Motor Case Study.” Columbia University. 2012.
Akbari, Pejman. “DC Motor Characteristics.” Lecture. 2012. 9. Appendix 21...
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- Fall '13
- Mechanical Engineering