SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

Returning to Figure 2.8, when an external force is applied to the rod, a voltage is induced
according to Faraday’s law. Since an external resistance is connected, a current flows and
dissipates heat in the resistor. To satisfy conservation of energy Equation (2.13) must be satisfied
(the mechanical work input must equal the electrical energy dissipated in the resistor).
F v g i
(2.13)
The apparatus in Figure 2.8 is an elementary, ideal linear generator with a load: mechanical
energy is converted into electrical energy which is then dissipated as heat energy. Now, instead of
the resistance serving as a kludge to allow the application of Lenz’s law, let the resistance
represent the distributed resistance of a real coil lumped into one element and let this coil be
driven by an external voltage source. The apparatus now functions as a linear motor, converting
electrical energy into mechanical work. Whereas previously FAPPLIED was exerted to generate a
current, here a current is made to flow and it produces FDEVELOPED, as shown in Figure 2.10.
Figure 2.10 – Demonstration of the Lorentz Force law; motor.
In the same way that an electrical model (Figure 2.9) was created to represent the apparatus of
Figure 2.8, an electrical model (Figure 2.11) can be created to represent the apparatus of Figure
2.10.
Figure 2.11 – Electrical model of coil connected to voltage source.
The above discussion demonstrates that any time the flux linkage of a coil changes, a voltage is
induced in the coil. The mechanism responsible for the induced voltage is the same mechanism
responsible for the applied (or developed) force acting on the coil itself. This result will be
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