Help with the problems in Electric Generators
Problem 1.1: parts (a) and (b) are independent of (c) and (d). In part (d), each generator is rated at 7.222 MVA.
Problem 1.3: in parts (c) and (d), use an RPM range that corresponds to the range of lambda used previously.
Problems 3.3 and 3.4: use time-domain expressions for the voltages (not phasors).
The voltage
at one point is the difference between the voltages at that point and at the ground.
The voltage on a winding is the difference between the
voltages at the two terminals.
The voltage at the mid-point of a
winding is the average of the voltages at the end points.
Problem 4.3:
compute the impedance Z of a resistance in parallel with a capacitance.
Then, PF = cos (angle(Z)). If Z=R+jX, then cos(ϕ)=R/|Z|.
Problem 5.4:
parts (a) and (b), run the simulation at constant speed to find the
operating points.
The absorbed mechanical power is the torque (variable
tau) times the speed (variable om).
Be careful with the signs of absorbed vs generated power.
Problem 5.5: use the peak voltage to obtain the line-to-line rms value.
Problem 6.2:
recall that the magnitude of the phasors is defined in the book as the
peak magnitude of line-to-neutral voltages and the peak magnitude for
line currents.
Use conversion factors from chapter 3 to derive rms and line-to-line values.
In
(b), the maximum power should correspond to the point P3 in Fig. 6.20,
with Q=0 and I= Imax.
The power is different from Pmax in Fig. 6.13
with Q<0, a larger E, and a current greater than Imax.
Problem 7.1: recall that, in Matlab, x=[x1;x2] defines a 2x1 column vector and x=[x1 x2] defines a 1x2 row vector.
In both cases, x1=x(1) and x2=x(2). The vectors in the generator blocks are column vectors.
It
is useful to define the size of variables using x=[0;0] at the
beginning of an m-file or as the initial condition of an integrator.
The dimensions of Inports and Outports in sub-blocks are found by double-clicking on the port, then choosing attributes.
The
dimension is set to -1 by default, which means that Simulink will
figure out the dimensions from other signals in the system.
Sometimes, it helps to set the dimension of the port.
However,
problems can arise when using copy/paste for ports and integrators, as
the dimension is also copied and may not fit the location of pasting.
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of the
Department of Electrical and Computer
Engineering
at the University of Utah.
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For questions or comments, please send an e-mail to marc.bodson@utah.edu.
Last updated: May 29, 2024.