Massachusetts Institute of Technology
Department of Electrical Engineering and Computer Science
6.685 Electric Machinery
Quiz 1 One Crib Sheet Allowed November 6, 2013
There is space for you to write your answers on this quiz.
There are four problems on this quiz. They have equal weight
Problem 1: Induction Motors
The single phase equivalent circuit of a three-phase, four pole induction m otor is shown in
Figure 1. For the purposes of this problem we will assume armature resistance is negligible.
The machine is connected to a three-phase voltage source with line-neutral voltage of 200
volts, RMS (346 volts, line-line) and a frequency of 400 radians/second. The motor reaches
peak torque at a speed of 160 Radians/second (about 1528 RPM).
j 2.5Ω j 2 Ω
Ωj 10 s
200 v
+
−
R2
Figure 1: Induction Motor Equivalent Circuit
1. What is the value of that peak torque (in N-m)?
2. What is the value of R2? (in Ω)
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