Appeal No. 1996-1427
Application 08/029,028
constitute all of the pending claims in the application before us.
BACKGROUND
The subject matter on appeal is directed to control electronics for an induction motor (i.e.,
polyphase inverter), and more specifically to an appartus and method for controlling slip frequency of a
motor so as to eliminate clipping of AC motor drive signals throughout an operating range of the motor
(see appellants’ Figure 2 and page 1 of the specification). As stated by appellant at page 2 of the
specification, clipping of the output voltage of the motor reduces its efficiency and increases instability.
The control or anti-clipping circuit of the invention of claims 1 to 7 on appeal includes a means for (see
representative claim 1), and step for (see representative claim 6), adjusting slip frequency as a function
of a comparison output in order to progressively increase slip frequency as the electromotive force of
the motor nears the power supply voltage. The comparison output is the result of a comparison
between a power supply voltage and the electromotive force of the motor. As stated by applicant in
the Summary of the Invention section of the specification, "[t]he inverter can thus operate at maximum
modulation anywhere in the operating range of the motor without clipping the output voltage sine wave"
which "allows maximum power output and efficiency over the entire operating range" (specification,
page 4). Thus, as motor peak output voltage approaches the power supply voltage level, motor drive
waveforms are not distorted (see specification, page 4).
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