CONCLUSION
A new digital technique to determine the torque-speed characteristics
of induction motors, in accordance with the acceleration
method of the IEEE standard test procedure for polyphase induction
motors and generators, has been presented. In contrast to
other currently available methods, this technique has the advantage
of eliminating all extraneous noise and disturbance signals
while preserving the actual characteristics of the machine.
The digital data processing and algorithms used to realise the
advantages of this technique have also been discussed. The use of
these algorithms is not restricted to this application only. The
digital scope, the dynamic window averaging and the new differentiation
algorithms provide unique and powferful tools to handle a
wide range of contaminated signals, such as those observed during
transient conditions. The validity of these algorithms have been
verified by investigating the data produced during the steady state
and run down operation of the machine. This investigation was also
crucial in establishing the size of the various windows used, and to
systematically identify the disturbance signals.
The data acquisition system used to collect and store the desired
information offers a high degree of flexibility as far as the amount
of collected data and sampling rate are concerned. The availability
of accurate measurements of other variables in the system is very
beneficial in assessing the torque profile of the machine and for
trouble shooting tasks that may be required.
The approach described in this paper can be automated to a large
extent to form a standard test method in the manufacturing of
induction motors.