Work on separate sheets of paper. Must be turned in at beginning of class. First page blank
with only your name and should be stapled. Homework will be collected promptly at 2:30. If
not submitted in time, it will not be graded.
1. A 3stack VRSM with 4 rotor teeth is to be operated at an average speed of 200 rpm (revolu
tions per minute). What is the step length
in degrees? Assuming the phase currents are 0 or
(only one phase on at a time), sketch one full period of
indicating the times it is zero
and nonzero. What is the frequency of the phase current in rad/s?
2. The following stepping sequence is applied to a 3phase VRSM with 4 rotor teeth:
,
to
,
, to
,
. Initially,
.
The rotor position is allowed to settle to a constant after each step. Sketch the corresponding tra
jectory below and indicate the rotor positions after each step (you are to turn in this sheet). What
is the final value of
in degrees? Assume
.
Neglect overshoot.
3. For a given phase (stack) in the VRSM of Problem 1, the maximum selfinductance is 40 mH
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 Spring '08
 Staff
 Frequency, Trigraph, Revolutions per minute, VRSM, maximum load torque

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